Class Scanner
- java.lang.Object
-
- java.util.Scanner
- All Implemented Interfaces:
-
Closeable
,AutoCloseable
,Iterator<String>
public final class Scanner extends Object implements Iterator<String>, Closeable
A simple text scanner which can parse primitive types and strings using regular expressions.
A Scanner
breaks its input into tokens using a delimiter pattern, which by default matches whitespace. The resulting tokens may then be converted into values of different types using the various next
methods.
For example, this code allows a user to read a number from System.in
:
Scanner sc = new Scanner(System.in); int i = sc.nextInt();
As another example, this code allows long
types to be assigned from entries in a file myNumbers
:
Scanner sc = new Scanner(new File("myNumbers")); while (sc.hasNextLong()) { long aLong = sc.nextLong(); }
The scanner can also use delimiters other than whitespace. This example reads several items in from a string:
String input = "1 fish 2 fish red fish blue fish"; Scanner s = new Scanner(input).useDelimiter("\\s*fish\\s*"); System.out.println(s.nextInt()); System.out.println(s.nextInt()); System.out.println(s.next()); System.out.println(s.next()); s.close();
prints the following output:
1 2 red blue
The same output can be generated with this code, which uses a regular expression to parse all four tokens at once:
String input = "1 fish 2 fish red fish blue fish"; Scanner s = new Scanner(input); s.findInLine("(\\d+) fish (\\d+) fish (\\w+) fish (\\w+)"); MatchResult result = s.match(); for (int i=1; i<=result.groupCount(); i++) System.out.println(result.group(i)); s.close();
The default whitespace delimiter used by a scanner is as recognized by Character.isWhitespace()
. The reset()
method will reset the value of the scanner's delimiter to the default whitespace delimiter regardless of whether it was previously changed.
A scanning operation may block waiting for input.
The next()
and hasNext()
methods and their companion methods (such as nextInt()
and hasNextInt()
) first skip any input that matches the delimiter pattern, and then attempt to return the next token. Both hasNext()
and next()
methods may block waiting for further input. Whether a hasNext()
method blocks has no connection to whether or not its associated next()
method will block. The tokens()
method may also block waiting for input.
The findInLine()
, findWithinHorizon()
, skip()
, and findAll()
methods operate independently of the delimiter pattern. These methods will attempt to match the specified pattern with no regard to delimiters in the input and thus can be used in special circumstances where delimiters are not relevant. These methods may block waiting for more input.
When a scanner throws an InputMismatchException
, the scanner will not pass the token that caused the exception, so that it may be retrieved or skipped via some other method.
Depending upon the type of delimiting pattern, empty tokens may be returned. For example, the pattern "\\s+"
will return no empty tokens since it matches multiple instances of the delimiter. The delimiting pattern "\\s"
could return empty tokens since it only passes one space at a time.
A scanner can read text from any object which implements the Readable
interface. If an invocation of the underlying readable's read()
method throws an IOException
then the scanner assumes that the end of the input has been reached. The most recent IOException
thrown by the underlying readable can be retrieved via the ioException()
method.
When a Scanner
is closed, it will close its input source if the source implements the Closeable
interface.
A Scanner
is not safe for multithreaded use without external synchronization.
Unless otherwise mentioned, passing a null
parameter into any method of a Scanner
will cause a NullPointerException
to be thrown.
A scanner will default to interpreting numbers as decimal unless a different radix has been set by using the useRadix(int)
method. The reset()
method will reset the value of the scanner's radix to 10
regardless of whether it was previously changed.
Localized numbers
An instance of this class is capable of scanning numbers in the standard formats as well as in the formats of the scanner's locale. A scanner's initial locale is the value returned by the Locale.getDefault(Locale.Category.FORMAT)
method; it may be changed via the useLocale()
method. The reset()
method will reset the value of the scanner's locale to the initial locale regardless of whether it was previously changed.
The localized formats are defined in terms of the following parameters, which for a particular locale are taken from that locale's DecimalFormat
object, df
, and its and DecimalFormatSymbols
object, dfs
.
- LocalGroupSeparator
- The character used to separate thousands groups, i.e.,
dfs.
getGroupingSeparator()
- LocalDecimalSeparator
- The character used for the decimal point, i.e.,
dfs.
getDecimalSeparator()
- LocalPositivePrefix
- The string that appears before a positive number (may be empty), i.e.,
df.
getPositivePrefix()
- LocalPositiveSuffix
- The string that appears after a positive number (may be empty), i.e.,
df.
getPositiveSuffix()
- LocalNegativePrefix
- The string that appears before a negative number (may be empty), i.e.,
df.
getNegativePrefix()
- LocalNegativeSuffix
- The string that appears after a negative number (may be empty), i.e.,
df.
getNegativeSuffix()
- LocalNaN
- The string that represents not-a-number for floating-point values, i.e.,
dfs.
getNaN()
- LocalInfinity
- The string that represents infinity for floating-point values, i.e.,
dfs.
getInfinity()
Number syntax
The strings that can be parsed as numbers by an instance of this class are specified in terms of the following regular-expression grammar, where Rmax is the highest digit in the radix being used (for example, Rmax is 9 in base 10).
- NonAsciiDigit:
- A non-ASCII character c for which
Character.isDigit
(c)
returns true - Non0Digit:
-
[1-
Rmax] |
NonASCIIDigit - Digit:
-
[0-
Rmax] |
NonASCIIDigit - GroupedNumeral:
-
(
Non0Digit Digit?
Digit?
(
LocalGroupSeparator Digit Digit Digit)+ )
- Numeral:
-
( (
Digit+ ) |
GroupedNumeral)
- Integer:
-
( [-+]? (
Numeral) )
|
LocalPositivePrefix Numeral LocalPositiveSuffix|
LocalNegativePrefix Numeral LocalNegativeSuffix - DecimalNumeral:
-
Numeral
|
Numeral LocalDecimalSeparator Digit*
|
LocalDecimalSeparator Digit+
- Exponent:
-
( [eE] [+-]?
Digit+ )
- Decimal:
-
( [-+]?
DecimalNumeral Exponent? )
|
LocalPositivePrefix DecimalNumeral LocalPositiveSuffix Exponent?
|
LocalNegativePrefix DecimalNumeral LocalNegativeSuffix Exponent?
- HexFloat:
-
[-+]? 0[xX][0-9a-fA-F]*\.[0-9a-fA-F]+ ([pP][-+]?[0-9]+)?
- NonNumber:
-
NaN |
LocalNan| Infinity |
LocalInfinity - SignedNonNumber:
-
( [-+]?
NonNumber)
|
LocalPositivePrefix NonNumber LocalPositiveSuffix|
LocalNegativePrefix NonNumber LocalNegativeSuffix - Float:
-
Decimal
|
HexFloat|
SignedNonNumber
Whitespace is not significant in the above regular expressions.
- Since:
- 1.5
Constructor Summary
Constructor | Description |
---|---|
Scanner(File source) | Constructs a new |
Scanner(File source,
String charsetName) | Constructs a new |
Scanner(File source,
Charset charset) | Constructs a new |
Scanner(InputStream source) | Constructs a new |
Scanner(InputStream source,
String charsetName) | Constructs a new |
Scanner(InputStream source,
Charset charset) | Constructs a new |
Scanner(Readable source) | Constructs a new |
Scanner(String source) | Constructs a new |
Scanner(ReadableByteChannel source) | Constructs a new |
Scanner(ReadableByteChannel source,
String charsetName) | Constructs a new |
Scanner(ReadableByteChannel source,
Charset charset) | Constructs a new |
Scanner(Path source) | Constructs a new |
Scanner(Path source,
String charsetName) | Constructs a new |
Scanner(Path source,
Charset charset) | Constructs a new |
Method Summary
Modifier and Type | Method | Description |
---|---|---|
void | close() | Closes this scanner. |
Pattern | delimiter() | Returns the |
Stream<MatchResult> | findAll(String patString) | Returns a stream of match results that match the provided pattern string. |
Stream<MatchResult> | findAll(Pattern pattern) | Returns a stream of match results from this scanner. |
String | findInLine(String pattern) | Attempts to find the next occurrence of a pattern constructed from the specified string, ignoring delimiters. |
String | findInLine(Pattern pattern) | Attempts to find the next occurrence of the specified pattern ignoring delimiters. |
String | findWithinHorizon(String pattern,
int horizon) | Attempts to find the next occurrence of a pattern constructed from the specified string, ignoring delimiters. |
String | findWithinHorizon(Pattern pattern,
int horizon) | Attempts to find the next occurrence of the specified pattern. |
boolean | hasNext() | Returns true if this scanner has another token in its input. |
boolean | hasNext(String pattern) | Returns true if the next token matches the pattern constructed from the specified string. |
boolean | hasNext(Pattern pattern) | Returns true if the next complete token matches the specified pattern. |
boolean | hasNextBigDecimal() | Returns true if the next token in this scanner's input can be interpreted as a |
boolean | hasNextBigInteger() | Returns true if the next token in this scanner's input can be interpreted as a |
boolean | hasNextBigInteger(int radix) | Returns true if the next token in this scanner's input can be interpreted as a |
boolean | hasNextBoolean() | Returns true if the next token in this scanner's input can be interpreted as a boolean value using a case insensitive pattern created from the string "true|false". |
boolean | hasNextByte() | Returns true if the next token in this scanner's input can be interpreted as a byte value in the default radix using the |
boolean | hasNextByte(int radix) | Returns true if the next token in this scanner's input can be interpreted as a byte value in the specified radix using the |
boolean | hasNextDouble() | Returns true if the next token in this scanner's input can be interpreted as a double value using the |
boolean | hasNextFloat() | Returns true if the next token in this scanner's input can be interpreted as a float value using the |
boolean | hasNextInt() | Returns true if the next token in this scanner's input can be interpreted as an int value in the default radix using the |
boolean | hasNextInt(int radix) | Returns true if the next token in this scanner's input can be interpreted as an int value in the specified radix using the |
boolean | hasNextLine() | Returns true if there is another line in the input of this scanner. |
boolean | hasNextLong() | Returns true if the next token in this scanner's input can be interpreted as a long value in the default radix using the |
boolean | hasNextLong(int radix) | Returns true if the next token in this scanner's input can be interpreted as a long value in the specified radix using the |
boolean | hasNextShort() | Returns true if the next token in this scanner's input can be interpreted as a short value in the default radix using the |
boolean | hasNextShort(int radix) | Returns true if the next token in this scanner's input can be interpreted as a short value in the specified radix using the |
IOException | ioException() | Returns the |
Locale | locale() | Returns this scanner's locale. |
MatchResult | match() | Returns the match result of the last scanning operation performed by this scanner. |
String | next() | Finds and returns the next complete token from this scanner. |
String | next(String pattern) | Returns the next token if it matches the pattern constructed from the specified string. |
String | next(Pattern pattern) | Returns the next token if it matches the specified pattern. |
BigDecimal | nextBigDecimal() | Scans the next token of the input as a |
BigInteger | nextBigInteger() | Scans the next token of the input as a |
BigInteger | nextBigInteger(int radix) | Scans the next token of the input as a |
boolean | nextBoolean() | Scans the next token of the input into a boolean value and returns that value. |
byte | nextByte() | Scans the next token of the input as a |
byte | nextByte(int radix) | Scans the next token of the input as a |
double | nextDouble() | Scans the next token of the input as a |
float | nextFloat() | Scans the next token of the input as a |
int | nextInt() | Scans the next token of the input as an |
int | nextInt(int radix) | Scans the next token of the input as an |
String | nextLine() | Advances this scanner past the current line and returns the input that was skipped. |
long | nextLong() | Scans the next token of the input as a |
long | nextLong(int radix) | Scans the next token of the input as a |
short | nextShort() | Scans the next token of the input as a |
short | nextShort(int radix) | Scans the next token of the input as a |
int | radix() | Returns this scanner's default radix. |
void | remove() | The remove operation is not supported by this implementation of |
Scanner | reset() | Resets this scanner. |
Scanner | skip(String pattern) | Skips input that matches a pattern constructed from the specified string. |
Scanner | skip(Pattern pattern) | Skips input that matches the specified pattern, ignoring delimiters. |
Stream<String> | tokens() | Returns a stream of delimiter-separated tokens from this scanner. |
String | toString() | Returns the string representation of this |
Scanner | useDelimiter(String pattern) | Sets this scanner's delimiting pattern to a pattern constructed from the specified |
Scanner | useDelimiter(Pattern pattern) | Sets this scanner's delimiting pattern to the specified pattern. |
Scanner | useLocale(Locale locale) | Sets this scanner's locale to the specified locale. |
Scanner | useRadix(int radix) | Sets this scanner's default radix to the specified radix. |
Methods declared in class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait
Methods declared in interface java.util.Iterator
forEachRemaining
Constructor Detail
Scanner
public Scanner(Readable source)
Constructs a new Scanner
that produces values scanned from the specified source.
- Parameters:
-
source
- A character source implementing theReadable
interface
Scanner
public Scanner(InputStream source)
Constructs a new Scanner
that produces values scanned from the specified input stream. Bytes from the stream are converted into characters using the underlying platform's default charset.
- Parameters:
-
source
- An input stream to be scanned
Scanner
public Scanner(InputStream source, String charsetName)
Constructs a new Scanner
that produces values scanned from the specified input stream. Bytes from the stream are converted into characters using the specified charset.
- Parameters:
-
source
- An input stream to be scanned -
charsetName
- The encoding type used to convert bytes from the stream into characters to be scanned - Throws:
-
IllegalArgumentException
- if the specified character set does not exist
Scanner
public Scanner(InputStream source, Charset charset)
Constructs a new Scanner
that produces values scanned from the specified input stream. Bytes from the stream are converted into characters using the specified charset.
- Parameters:
-
source
- an input stream to be scanned -
charset
- the charset used to convert bytes from the file into characters to be scanned - Since:
- 10
Scanner
public Scanner(File source) throws FileNotFoundException
Constructs a new Scanner
that produces values scanned from the specified file. Bytes from the file are converted into characters using the underlying platform's default charset.
- Parameters:
-
source
- A file to be scanned - Throws:
-
FileNotFoundException
- if source is not found
Scanner
public Scanner(File source, String charsetName) throws FileNotFoundException
Constructs a new Scanner
that produces values scanned from the specified file. Bytes from the file are converted into characters using the specified charset.
- Parameters:
-
source
- A file to be scanned -
charsetName
- The encoding type used to convert bytes from the file into characters to be scanned - Throws:
-
FileNotFoundException
- if source is not found -
IllegalArgumentException
- if the specified encoding is not found
Scanner
public Scanner(File source, Charset charset) throws IOException
Constructs a new Scanner
that produces values scanned from the specified file. Bytes from the file are converted into characters using the specified charset.
- Parameters:
-
source
- A file to be scanned -
charset
- The charset used to convert bytes from the file into characters to be scanned - Throws:
-
IOException
- if an I/O error occurs opening the source - Since:
- 10
Scanner
public Scanner(Path source) throws IOException
Constructs a new Scanner
that produces values scanned from the specified file. Bytes from the file are converted into characters using the underlying platform's default charset.
- Parameters:
-
source
- the path to the file to be scanned - Throws:
-
IOException
- if an I/O error occurs opening source - Since:
- 1.7
Scanner
public Scanner(Path source, String charsetName) throws IOException
Constructs a new Scanner
that produces values scanned from the specified file. Bytes from the file are converted into characters using the specified charset.
- Parameters:
-
source
- the path to the file to be scanned -
charsetName
- The encoding type used to convert bytes from the file into characters to be scanned - Throws:
-
IOException
- if an I/O error occurs opening source -
IllegalArgumentException
- if the specified encoding is not found - Since:
- 1.7
Scanner
public Scanner(Path source, Charset charset) throws IOException
Constructs a new Scanner
that produces values scanned from the specified file. Bytes from the file are converted into characters using the specified charset.
- Parameters:
-
source
- the path to the file to be scanned -
charset
- the charset used to convert bytes from the file into characters to be scanned - Throws:
-
IOException
- if an I/O error occurs opening the source - Since:
- 10
Scanner
public Scanner(String source)
Constructs a new Scanner
that produces values scanned from the specified string.
- Parameters:
-
source
- A string to scan
Scanner
public Scanner(ReadableByteChannel source)
Constructs a new Scanner
that produces values scanned from the specified channel. Bytes from the source are converted into characters using the underlying platform's default charset.
- Parameters:
-
source
- A channel to scan
Scanner
public Scanner(ReadableByteChannel source, String charsetName)
Constructs a new Scanner
that produces values scanned from the specified channel. Bytes from the source are converted into characters using the specified charset.
- Parameters:
-
source
- A channel to scan -
charsetName
- The encoding type used to convert bytes from the channel into characters to be scanned - Throws:
-
IllegalArgumentException
- if the specified character set does not exist
Scanner
public Scanner(ReadableByteChannel source, Charset charset)
Constructs a new Scanner
that produces values scanned from the specified channel. Bytes from the source are converted into characters using the specified charset.
- Parameters:
-
source
- a channel to scan -
charset
- the encoding type used to convert bytes from the channel into characters to be scanned - Since:
- 10
Method Detail
close
public void close()
Closes this scanner.
If this scanner has not yet been closed then if its underlying readable also implements the Closeable
interface then the readable's close
method will be invoked. If this scanner is already closed then invoking this method will have no effect.
Attempting to perform search operations after a scanner has been closed will result in an IllegalStateException
.
- Specified by:
-
close
in interfaceAutoCloseable
- Specified by:
-
close
in interfaceCloseable
ioException
public IOException ioException()
Returns the IOException
last thrown by this Scanner
's underlying Readable
. This method returns null
if no such exception exists.
- Returns:
- the last exception thrown by this scanner's readable
delimiter
public Pattern delimiter()
Returns the Pattern
this Scanner
is currently using to match delimiters.
- Returns:
- this scanner's delimiting pattern.
useDelimiter
public Scanner useDelimiter(Pattern pattern)
Sets this scanner's delimiting pattern to the specified pattern.
- Parameters:
-
pattern
- A delimiting pattern - Returns:
- this scanner
useDelimiter
public Scanner useDelimiter(String pattern)
Sets this scanner's delimiting pattern to a pattern constructed from the specified String
.
An invocation of this method of the form useDelimiter(pattern)
behaves in exactly the same way as the invocation useDelimiter(Pattern.compile(pattern))
.
Invoking the reset()
method will set the scanner's delimiter to the default.
- Parameters:
-
pattern
- A string specifying a delimiting pattern - Returns:
- this scanner
locale
public Locale locale()
Returns this scanner's locale.
A scanner's locale affects many elements of its default primitive matching regular expressions; see localized numbers above.
- Returns:
- this scanner's locale
useLocale
public Scanner useLocale(Locale locale)
Sets this scanner's locale to the specified locale.
A scanner's locale affects many elements of its default primitive matching regular expressions; see localized numbers above.
Invoking the reset()
method will set the scanner's locale to the initial locale.
- Parameters:
-
locale
- A string specifying the locale to use - Returns:
- this scanner
radix
public int radix()
Returns this scanner's default radix.
A scanner's radix affects elements of its default number matching regular expressions; see localized numbers above.
- Returns:
- the default radix of this scanner
useRadix
public Scanner useRadix(int radix)
Sets this scanner's default radix to the specified radix.
A scanner's radix affects elements of its default number matching regular expressions; see localized numbers above.
If the radix is less than Character.MIN_RADIX
or greater than Character.MAX_RADIX
, then an IllegalArgumentException
is thrown.
Invoking the reset()
method will set the scanner's radix to 10
.
- Parameters:
-
radix
- The radix to use when scanning numbers - Returns:
- this scanner
- Throws:
-
IllegalArgumentException
- if radix is out of range
match
public MatchResult match()
Returns the match result of the last scanning operation performed by this scanner. This method throws IllegalStateException
if no match has been performed, or if the last match was not successful.
The various next
methods of Scanner
make a match result available if they complete without throwing an exception. For instance, after an invocation of the nextInt()
method that returned an int, this method returns a MatchResult
for the search of the Integer regular expression defined above. Similarly the findInLine()
, findWithinHorizon()
, and skip()
methods will make a match available if they succeed.
- Returns:
- a match result for the last match operation
- Throws:
-
IllegalStateException
- If no match result is available
toString
public String toString()
Returns the string representation of this Scanner
. The string representation of a Scanner
contains information that may be useful for debugging. The exact format is unspecified.
hasNext
public boolean hasNext()
Returns true if this scanner has another token in its input. This method may block while waiting for input to scan. The scanner does not advance past any input.
- Specified by:
-
hasNext
in interfaceIterator<String>
- Returns:
- true if and only if this scanner has another token
- Throws:
-
IllegalStateException
- if this scanner is closed - See Also:
Iterator
next
public String next()
Finds and returns the next complete token from this scanner. A complete token is preceded and followed by input that matches the delimiter pattern. This method may block while waiting for input to scan, even if a previous invocation of hasNext()
returned true
.
- Specified by:
-
next
in interfaceIterator<String>
- Returns:
- the next token
- Throws:
-
NoSuchElementException
- if no more tokens are available -
IllegalStateException
- if this scanner is closed - See Also:
Iterator
remove
public void remove()
The remove operation is not supported by this implementation of Iterator
.
- Specified by:
-
remove
in interfaceIterator<String>
- Throws:
-
UnsupportedOperationException
- if this method is invoked. - See Also:
Iterator
hasNext
public boolean hasNext(String pattern)
Returns true if the next token matches the pattern constructed from the specified string. The scanner does not advance past any input.
An invocation of this method of the form hasNext(pattern)
behaves in exactly the same way as the invocation hasNext(Pattern.compile(pattern))
.
- Parameters:
-
pattern
- a string specifying the pattern to scan - Returns:
- true if and only if this scanner has another token matching the specified pattern
- Throws:
-
IllegalStateException
- if this scanner is closed
next
public String next(String pattern)
Returns the next token if it matches the pattern constructed from the specified string. If the match is successful, the scanner advances past the input that matched the pattern.
An invocation of this method of the form next(pattern)
behaves in exactly the same way as the invocation next(Pattern.compile(pattern))
.
- Parameters:
-
pattern
- a string specifying the pattern to scan - Returns:
- the next token
- Throws:
-
NoSuchElementException
- if no such tokens are available -
IllegalStateException
- if this scanner is closed
hasNext
public boolean hasNext(Pattern pattern)
Returns true if the next complete token matches the specified pattern. A complete token is prefixed and postfixed by input that matches the delimiter pattern. This method may block while waiting for input. The scanner does not advance past any input.
- Parameters:
-
pattern
- the pattern to scan for - Returns:
- true if and only if this scanner has another token matching the specified pattern
- Throws:
-
IllegalStateException
- if this scanner is closed
next
public String next(Pattern pattern)
Returns the next token if it matches the specified pattern. This method may block while waiting for input to scan, even if a previous invocation of hasNext(Pattern)
returned true
. If the match is successful, the scanner advances past the input that matched the pattern.
- Parameters:
-
pattern
- the pattern to scan for - Returns:
- the next token
- Throws:
-
NoSuchElementException
- if no more tokens are available -
IllegalStateException
- if this scanner is closed
hasNextLine
public boolean hasNextLine()
Returns true if there is another line in the input of this scanner. This method may block while waiting for input. The scanner does not advance past any input.
- Returns:
- true if and only if this scanner has another line of input
- Throws:
-
IllegalStateException
- if this scanner is closed
nextLine
public String nextLine()
Advances this scanner past the current line and returns the input that was skipped. This method returns the rest of the current line, excluding any line separator at the end. The position is set to the beginning of the next line.
Since this method continues to search through the input looking for a line separator, it may buffer all of the input searching for the line to skip if no line separators are present.
- Returns:
- the line that was skipped
- Throws:
-
NoSuchElementException
- if no line was found -
IllegalStateException
- if this scanner is closed
findInLine
public String findInLine(String pattern)
Attempts to find the next occurrence of a pattern constructed from the specified string, ignoring delimiters.
An invocation of this method of the form findInLine(pattern)
behaves in exactly the same way as the invocation findInLine(Pattern.compile(pattern))
.
- Parameters:
-
pattern
- a string specifying the pattern to search for - Returns:
- the text that matched the specified pattern
- Throws:
-
IllegalStateException
- if this scanner is closed
findInLine
public String findInLine(Pattern pattern)
Attempts to find the next occurrence of the specified pattern ignoring delimiters. If the pattern is found before the next line separator, the scanner advances past the input that matched and returns the string that matched the pattern. If no such pattern is detected in the input up to the next line separator, then null
is returned and the scanner's position is unchanged. This method may block waiting for input that matches the pattern.
Since this method continues to search through the input looking for the specified pattern, it may buffer all of the input searching for the desired token if no line separators are present.
- Parameters:
-
pattern
- the pattern to scan for - Returns:
- the text that matched the specified pattern
- Throws:
-
IllegalStateException
- if this scanner is closed
findWithinHorizon
public String findWithinHorizon(String pattern, int horizon)
Attempts to find the next occurrence of a pattern constructed from the specified string, ignoring delimiters.
An invocation of this method of the form findWithinHorizon(pattern)
behaves in exactly the same way as the invocation findWithinHorizon(Pattern.compile(pattern), horizon)
.
- Parameters:
-
pattern
- a string specifying the pattern to search for -
horizon
- the search horizon - Returns:
- the text that matched the specified pattern
- Throws:
-
IllegalStateException
- if this scanner is closed -
IllegalArgumentException
- if horizon is negative
findWithinHorizon
public String findWithinHorizon(Pattern pattern, int horizon)
Attempts to find the next occurrence of the specified pattern.
This method searches through the input up to the specified search horizon, ignoring delimiters. If the pattern is found the scanner advances past the input that matched and returns the string that matched the pattern. If no such pattern is detected then the null is returned and the scanner's position remains unchanged. This method may block waiting for input that matches the pattern.
A scanner will never search more than horizon
code points beyond its current position. Note that a match may be clipped by the horizon; that is, an arbitrary match result may have been different if the horizon had been larger. The scanner treats the horizon as a transparent, non-anchoring bound (see Matcher.useTransparentBounds(boolean)
and Matcher.useAnchoringBounds(boolean)
).
If horizon is 0
, then the horizon is ignored and this method continues to search through the input looking for the specified pattern without bound. In this case it may buffer all of the input searching for the pattern.
If horizon is negative, then an IllegalArgumentException is thrown.
- Parameters:
-
pattern
- the pattern to scan for -
horizon
- the search horizon - Returns:
- the text that matched the specified pattern
- Throws:
-
IllegalStateException
- if this scanner is closed -
IllegalArgumentException
- if horizon is negative
skip
public Scanner skip(Pattern pattern)
Skips input that matches the specified pattern, ignoring delimiters. This method will skip input if an anchored match of the specified pattern succeeds.
If a match to the specified pattern is not found at the current position, then no input is skipped and a NoSuchElementException
is thrown.
Since this method seeks to match the specified pattern starting at the scanner's current position, patterns that can match a lot of input (".*", for example) may cause the scanner to buffer a large amount of input.
Note that it is possible to skip something without risking a NoSuchElementException
by using a pattern that can match nothing, e.g., sc.skip("[ \t]*")
.
- Parameters:
-
pattern
- a string specifying the pattern to skip over - Returns:
- this scanner
- Throws:
-
NoSuchElementException
- if the specified pattern is not found -
IllegalStateException
- if this scanner is closed
skip
public Scanner skip(String pattern)
Skips input that matches a pattern constructed from the specified string.
An invocation of this method of the form skip(pattern)
behaves in exactly the same way as the invocation skip(Pattern.compile(pattern))
.
- Parameters:
-
pattern
- a string specifying the pattern to skip over - Returns:
- this scanner
- Throws:
-
IllegalStateException
- if this scanner is closed
hasNextBoolean
public boolean hasNextBoolean()
Returns true if the next token in this scanner's input can be interpreted as a boolean value using a case insensitive pattern created from the string "true|false". The scanner does not advance past the input that matched.
- Returns:
- true if and only if this scanner's next token is a valid boolean value
- Throws:
-
IllegalStateException
- if this scanner is closed
nextBoolean
public boolean nextBoolean()
Scans the next token of the input into a boolean value and returns that value. This method will throw InputMismatchException
if the next token cannot be translated into a valid boolean value. If the match is successful, the scanner advances past the input that matched.
- Returns:
- the boolean scanned from the input
- Throws:
-
InputMismatchException
- if the next token is not a valid boolean -
NoSuchElementException
- if input is exhausted -
IllegalStateException
- if this scanner is closed
hasNextByte
public boolean hasNextByte()
Returns true if the next token in this scanner's input can be interpreted as a byte value in the default radix using the nextByte()
method. The scanner does not advance past any input.
- Returns:
- true if and only if this scanner's next token is a valid byte value
- Throws:
-
IllegalStateException
- if this scanner is closed
hasNextByte
public boolean hasNextByte(int radix)
Returns true if the next token in this scanner's input can be interpreted as a byte value in the specified radix using the nextByte()
method. The scanner does not advance past any input.
If the radix is less than Character.MIN_RADIX
or greater than Character.MAX_RADIX
, then an IllegalArgumentException
is thrown.
- Parameters:
-
radix
- the radix used to interpret the token as a byte value - Returns:
- true if and only if this scanner's next token is a valid byte value
- Throws:
-
IllegalStateException
- if this scanner is closed -
IllegalArgumentException
- if the radix is out of range
nextByte
public byte nextByte()
Scans the next token of the input as a byte
.
An invocation of this method of the form nextByte()
behaves in exactly the same way as the invocation nextByte(radix)
, where radix
is the default radix of this scanner.
- Returns:
- the
byte
scanned from the input - Throws:
-
InputMismatchException
- if the next token does not match the Integer regular expression, or is out of range -
NoSuchElementException
- if input is exhausted -
IllegalStateException
- if this scanner is closed
nextByte
public byte nextByte(int radix)
Scans the next token of the input as a byte
. This method will throw InputMismatchException
if the next token cannot be translated into a valid byte value as described below. If the translation is successful, the scanner advances past the input that matched.
If the next token matches the Integer regular expression defined above then the token is converted into a byte
value as if by removing all locale specific prefixes, group separators, and locale specific suffixes, then mapping non-ASCII digits into ASCII digits via Character.digit
, prepending a negative sign (-) if the locale specific negative prefixes and suffixes were present, and passing the resulting string to Byte.parseByte
with the specified radix.
If the radix is less than Character.MIN_RADIX
or greater than Character.MAX_RADIX
, then an IllegalArgumentException
is thrown.
- Parameters:
-
radix
- the radix used to interpret the token as a byte value - Returns:
- the
byte
scanned from the input - Throws:
-
InputMismatchException
- if the next token does not match the Integer regular expression, or is out of range -
NoSuchElementException
- if input is exhausted -
IllegalStateException
- if this scanner is closed -
IllegalArgumentException
- if the radix is out of range
hasNextShort
public boolean hasNextShort()
Returns true if the next token in this scanner's input can be interpreted as a short value in the default radix using the nextShort()
method. The scanner does not advance past any input.
- Returns:
- true if and only if this scanner's next token is a valid short value in the default radix
- Throws:
-
IllegalStateException
- if this scanner is closed
hasNextShort
public boolean hasNextShort(int radix)
Returns true if the next token in this scanner's input can be interpreted as a short value in the specified radix using the nextShort()
method. The scanner does not advance past any input.
If the radix is less than Character.MIN_RADIX
or greater than Character.MAX_RADIX
, then an IllegalArgumentException
is thrown.
- Parameters:
-
radix
- the radix used to interpret the token as a short value - Returns:
- true if and only if this scanner's next token is a valid short value in the specified radix
- Throws:
-
IllegalStateException
- if this scanner is closed -
IllegalArgumentException
- if the radix is out of range
nextShort
public short nextShort()
Scans the next token of the input as a short
.
An invocation of this method of the form nextShort()
behaves in exactly the same way as the invocation nextShort(radix)
, where radix
is the default radix of this scanner.
- Returns:
- the
short
scanned from the input - Throws:
-
InputMismatchException
- if the next token does not match the Integer regular expression, or is out of range -
NoSuchElementException
- if input is exhausted -
IllegalStateException
- if this scanner is closed
nextShort
public short nextShort(int radix)
Scans the next token of the input as a short
. This method will throw InputMismatchException
if the next token cannot be translated into a valid short value as described below. If the translation is successful, the scanner advances past the input that matched.
If the next token matches the Integer regular expression defined above then the token is converted into a short
value as if by removing all locale specific prefixes, group separators, and locale specific suffixes, then mapping non-ASCII digits into ASCII digits via Character.digit
, prepending a negative sign (-) if the locale specific negative prefixes and suffixes were present, and passing the resulting string to Short.parseShort
with the specified radix.
If the radix is less than Character.MIN_RADIX
or greater than Character.MAX_RADIX
, then an IllegalArgumentException
is thrown.
- Parameters:
-
radix
- the radix used to interpret the token as a short value - Returns:
- the
short
scanned from the input - Throws:
-
InputMismatchException
- if the next token does not match the Integer regular expression, or is out of range -
NoSuchElementException
- if input is exhausted -
IllegalStateException
- if this scanner is closed -
IllegalArgumentException
- if the radix is out of range
hasNextInt
public boolean hasNextInt()
Returns true if the next token in this scanner's input can be interpreted as an int value in the default radix using the nextInt()
method. The scanner does not advance past any input.
- Returns:
- true if and only if this scanner's next token is a valid int value
- Throws:
-
IllegalStateException
- if this scanner is closed
hasNextInt
public boolean hasNextInt(int radix)
Returns true if the next token in this scanner's input can be interpreted as an int value in the specified radix using the nextInt()
method. The scanner does not advance past any input.
If the radix is less than Character.MIN_RADIX
or greater than Character.MAX_RADIX
, then an IllegalArgumentException
is thrown.
- Parameters:
-
radix
- the radix used to interpret the token as an int value - Returns:
- true if and only if this scanner's next token is a valid int value
- Throws:
-
IllegalStateException
- if this scanner is closed -
IllegalArgumentException
- if the radix is out of range
nextInt
public int nextInt()
Scans the next token of the input as an int
.
An invocation of this method of the form nextInt()
behaves in exactly the same way as the invocation nextInt(radix)
, where radix
is the default radix of this scanner.
- Returns:
- the
int
scanned from the input - Throws:
-
InputMismatchException
- if the next token does not match the Integer regular expression, or is out of range -
NoSuchElementException
- if input is exhausted -
IllegalStateException
- if this scanner is closed
nextInt
public int nextInt(int radix)
Scans the next token of the input as an int
. This method will throw InputMismatchException
if the next token cannot be translated into a valid int value as described below. If the translation is successful, the scanner advances past the input that matched.
If the next token matches the Integer regular expression defined above then the token is converted into an int
value as if by removing all locale specific prefixes, group separators, and locale specific suffixes, then mapping non-ASCII digits into ASCII digits via Character.digit
, prepending a negative sign (-) if the locale specific negative prefixes and suffixes were present, and passing the resulting string to Integer.parseInt
with the specified radix.
If the radix is less than Character.MIN_RADIX
or greater than Character.MAX_RADIX
, then an IllegalArgumentException
is thrown.
- Parameters:
-
radix
- the radix used to interpret the token as an int value - Returns:
- the
int
scanned from the input - Throws:
-
InputMismatchException
- if the next token does not match the Integer regular expression, or is out of range -
NoSuchElementException
- if input is exhausted -
IllegalStateException
- if this scanner is closed -
IllegalArgumentException
- if the radix is out of range
hasNextLong
public boolean hasNextLong()
Returns true if the next token in this scanner's input can be interpreted as a long value in the default radix using the nextLong()
method. The scanner does not advance past any input.
- Returns:
- true if and only if this scanner's next token is a valid long value
- Throws:
-
IllegalStateException
- if this scanner is closed
hasNextLong
public boolean hasNextLong(int radix)
Returns true if the next token in this scanner's input can be interpreted as a long value in the specified radix using the nextLong()
method. The scanner does not advance past any input.
If the radix is less than Character.MIN_RADIX
or greater than Character.MAX_RADIX
, then an IllegalArgumentException
is thrown.
- Parameters:
-
radix
- the radix used to interpret the token as a long value - Returns:
- true if and only if this scanner's next token is a valid long value
- Throws:
-
IllegalStateException
- if this scanner is closed -
IllegalArgumentException
- if the radix is out of range
nextLong
public long nextLong()
Scans the next token of the input as a long
.
An invocation of this method of the form nextLong()
behaves in exactly the same way as the invocation nextLong(radix)
, where radix
is the default radix of this scanner.
- Returns:
- the
long
scanned from the input - Throws:
-
InputMismatchException
- if the next token does not match the Integer regular expression, or is out of range -
NoSuchElementException
- if input is exhausted -
IllegalStateException
- if this scanner is closed
nextLong
public long nextLong(int radix)
Scans the next token of the input as a long
. This method will throw InputMismatchException
if the next token cannot be translated into a valid long value as described below. If the translation is successful, the scanner advances past the input that matched.
If the next token matches the Integer regular expression defined above then the token is converted into a long
value as if by removing all locale specific prefixes, group separators, and locale specific suffixes, then mapping non-ASCII digits into ASCII digits via Character.digit
, prepending a negative sign (-) if the locale specific negative prefixes and suffixes were present, and passing the resulting string to Long.parseLong
with the specified radix.
If the radix is less than Character.MIN_RADIX
or greater than Character.MAX_RADIX
, then an IllegalArgumentException
is thrown.
- Parameters:
-
radix
- the radix used to interpret the token as an int value - Returns:
- the
long
scanned from the input - Throws:
-
InputMismatchException
- if the next token does not match the Integer regular expression, or is out of range -
NoSuchElementException
- if input is exhausted -
IllegalStateException
- if this scanner is closed -
IllegalArgumentException
- if the radix is out of range
hasNextFloat
public boolean hasNextFloat()
Returns true if the next token in this scanner's input can be interpreted as a float value using the nextFloat()
method. The scanner does not advance past any input.
- Returns:
- true if and only if this scanner's next token is a valid float value
- Throws:
-
IllegalStateException
- if this scanner is closed
nextFloat
public float nextFloat()
Scans the next token of the input as a float
. This method will throw InputMismatchException
if the next token cannot be translated into a valid float value as described below. If the translation is successful, the scanner advances past the input that matched.
If the next token matches the Float regular expression defined above then the token is converted into a float
value as if by removing all locale specific prefixes, group separators, and locale specific suffixes, then mapping non-ASCII digits into ASCII digits via Character.digit
, prepending a negative sign (-) if the locale specific negative prefixes and suffixes were present, and passing the resulting string to Float.parseFloat
. If the token matches the localized NaN or infinity strings, then either "Nan" or "Infinity" is passed to Float.parseFloat
as appropriate.
- Returns:
- the
float
scanned from the input - Throws:
-
InputMismatchException
- if the next token does not match the Float regular expression, or is out of range -
NoSuchElementException
- if input is exhausted -
IllegalStateException
- if this scanner is closed
hasNextDouble
public boolean hasNextDouble()
Returns true if the next token in this scanner's input can be interpreted as a double value using the nextDouble()
method. The scanner does not advance past any input.
- Returns:
- true if and only if this scanner's next token is a valid double value
- Throws:
-
IllegalStateException
- if this scanner is closed
nextDouble
public double nextDouble()
Scans the next token of the input as a double
. This method will throw InputMismatchException
if the next token cannot be translated into a valid double value. If the translation is successful, the scanner advances past the input that matched.
If the next token matches the Float regular expression defined above then the token is converted into a double
value as if by removing all locale specific prefixes, group separators, and locale specific suffixes, then mapping non-ASCII digits into ASCII digits via Character.digit
, prepending a negative sign (-) if the locale specific negative prefixes and suffixes were present, and passing the resulting string to Double.parseDouble
. If the token matches the localized NaN or infinity strings, then either "Nan" or "Infinity" is passed to Double.parseDouble
as appropriate.
- Returns:
- the
double
scanned from the input - Throws:
-
InputMismatchException
- if the next token does not match the Float regular expression, or is out of range -
NoSuchElementException
- if the input is exhausted -
IllegalStateException
- if this scanner is closed
hasNextBigInteger
public boolean hasNextBigInteger()
Returns true if the next token in this scanner's input can be interpreted as a BigInteger
in the default radix using the nextBigInteger()
method. The scanner does not advance past any input.
- Returns:
- true if and only if this scanner's next token is a valid
BigInteger
- Throws:
-
IllegalStateException
- if this scanner is closed
hasNextBigInteger
public boolean hasNextBigInteger(int radix)
Returns true if the next token in this scanner's input can be interpreted as a BigInteger
in the specified radix using the nextBigInteger()
method. The scanner does not advance past any input.
If the radix is less than Character.MIN_RADIX
or greater than Character.MAX_RADIX
, then an IllegalArgumentException
is thrown.
- Parameters:
-
radix
- the radix used to interpret the token as an integer - Returns:
- true if and only if this scanner's next token is a valid
BigInteger
- Throws:
-
IllegalStateException
- if this scanner is closed -
IllegalArgumentException
- if the radix is out of range
nextBigInteger
public BigInteger nextBigInteger()
Scans the next token of the input as a BigInteger
.
An invocation of this method of the form nextBigInteger()
behaves in exactly the same way as the invocation nextBigInteger(radix)
, where radix
is the default radix of this scanner.
- Returns:
- the
BigInteger
scanned from the input - Throws:
-
InputMismatchException
- if the next token does not match the Integer regular expression, or is out of range -
NoSuchElementException
- if the input is exhausted -
IllegalStateException
- if this scanner is closed
nextBigInteger
public BigInteger nextBigInteger(int radix)
Scans the next token of the input as a BigInteger
.
If the next token matches the Integer regular expression defined above then the token is converted into a BigInteger
value as if by removing all group separators, mapping non-ASCII digits into ASCII digits via the Character.digit
, and passing the resulting string to the BigInteger(String, int)
constructor with the specified radix.
If the radix is less than Character.MIN_RADIX
or greater than Character.MAX_RADIX
, then an IllegalArgumentException
is thrown.
- Parameters:
-
radix
- the radix used to interpret the token - Returns:
- the
BigInteger
scanned from the input - Throws:
-
InputMismatchException
- if the next token does not match the Integer regular expression, or is out of range -
NoSuchElementException
- if the input is exhausted -
IllegalStateException
- if this scanner is closed -
IllegalArgumentException
- if the radix is out of range
hasNextBigDecimal
public boolean hasNextBigDecimal()
Returns true if the next token in this scanner's input can be interpreted as a BigDecimal
using the nextBigDecimal()
method. The scanner does not advance past any input.
- Returns:
- true if and only if this scanner's next token is a valid
BigDecimal
- Throws:
-
IllegalStateException
- if this scanner is closed
nextBigDecimal
public BigDecimal nextBigDecimal()
Scans the next token of the input as a BigDecimal
.
If the next token matches the Decimal regular expression defined above then the token is converted into a BigDecimal
value as if by removing all group separators, mapping non-ASCII digits into ASCII digits via the Character.digit
, and passing the resulting string to the BigDecimal(String)
constructor.
- Returns:
- the
BigDecimal
scanned from the input - Throws:
-
InputMismatchException
- if the next token does not match the Decimal regular expression, or is out of range -
NoSuchElementException
- if the input is exhausted -
IllegalStateException
- if this scanner is closed
reset
public Scanner reset()
Resets this scanner.
Resetting a scanner discards all of its explicit state information which may have been changed by invocations of useDelimiter()
, useLocale()
, or useRadix()
.
An invocation of this method of the form scanner.reset()
behaves in exactly the same way as the invocation
scanner.useDelimiter("\\p{javaWhitespace}+") .useLocale(Locale.getDefault(Locale.Category.FORMAT)) .useRadix(10);
- Returns:
- this scanner
- Since:
- 1.6
tokens
public Stream<String> tokens()
Returns a stream of delimiter-separated tokens from this scanner. The stream contains the same tokens that would be returned, starting from this scanner's current state, by calling the next()
method repeatedly until the hasNext()
method returns false.
The resulting stream is sequential and ordered. All stream elements are non-null.
Scanning starts upon initiation of the terminal stream operation, using the current state of this scanner. Subsequent calls to any methods on this scanner other than close()
and ioException()
may return undefined results or may cause undefined effects on the returned stream. The returned stream's source Spliterator
is fail-fast and will, on a best-effort basis, throw a ConcurrentModificationException
if any such calls are detected during stream pipeline execution.
After stream pipeline execution completes, this scanner is left in an indeterminate state and cannot be reused.
If this scanner contains a resource that must be released, this scanner should be closed, either by calling its close()
method, or by closing the returned stream. Closing the stream will close the underlying scanner. IllegalStateException
is thrown if the scanner has been closed when this method is called, or if this scanner is closed during stream pipeline execution.
This method might block waiting for more input.
- API Note:
- For example, the following code will create a list of comma-delimited tokens from a string:
List<String> result = new Scanner("abc,def,,ghi") .useDelimiter(",") .tokens() .collect(Collectors.toList());
The resulting list would contain
"abc"
,"def"
, the empty string, and"ghi"
. - Returns:
- a sequential stream of token strings
- Throws:
-
IllegalStateException
- if this scanner is closed - Since:
- 9
findAll
public Stream<MatchResult> findAll(Pattern pattern)
Returns a stream of match results from this scanner. The stream contains the same results in the same order that would be returned by calling findWithinHorizon(pattern, 0)
and then match()
successively as long as findWithinHorizon()
finds matches.
The resulting stream is sequential and ordered. All stream elements are non-null.
Scanning starts upon initiation of the terminal stream operation, using the current state of this scanner. Subsequent calls to any methods on this scanner other than close()
and ioException()
may return undefined results or may cause undefined effects on the returned stream. The returned stream's source Spliterator
is fail-fast and will, on a best-effort basis, throw a ConcurrentModificationException
if any such calls are detected during stream pipeline execution.
After stream pipeline execution completes, this scanner is left in an indeterminate state and cannot be reused.
If this scanner contains a resource that must be released, this scanner should be closed, either by calling its close()
method, or by closing the returned stream. Closing the stream will close the underlying scanner. IllegalStateException
is thrown if the scanner has been closed when this method is called, or if this scanner is closed during stream pipeline execution.
As with the findWithinHorizon()
methods, this method might block waiting for additional input, and it might buffer an unbounded amount of input searching for a match.
- API Note:
- For example, the following code will read a file and return a list of all sequences of characters consisting of seven or more Latin capital letters:
try (Scanner sc = new Scanner(Path.of("input.txt"))) { Pattern pat = Pattern.compile("[A-Z]{7,}"); List<String> capWords = sc.findAll(pat) .map(MatchResult::group) .collect(Collectors.toList()); }
- Parameters:
-
pattern
- the pattern to be matched - Returns:
- a sequential stream of match results
- Throws:
-
NullPointerException
- if pattern is null -
IllegalStateException
- if this scanner is closed - Since:
- 9
findAll
public Stream<MatchResult> findAll(String patString)
Returns a stream of match results that match the provided pattern string. The effect is equivalent to the following code:
scanner.findAll(Pattern.compile(patString))
- Parameters:
-
patString
- the pattern string - Returns:
- a sequential stream of match results
- Throws:
-
NullPointerException
- if patString is null -
IllegalStateException
- if this scanner is closed -
PatternSyntaxException
- if the regular expression's syntax is invalid - Since:
- 9
- See Also:
Pattern