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/OpenJDK 21

Class PrintWriter

java.lang.Object
java.io.Writer
java.io.PrintWriter
All Implemented Interfaces:
Closeable, Flushable, Appendable, AutoCloseable 
public class PrintWriter extends Writer
Prints formatted representations of objects to a text-output stream. This class implements all of the print methods found in PrintStream. It does not contain methods for writing raw bytes, for which a program should use unencoded byte streams.

Unlike the PrintStream class, if automatic flushing is enabled it will be done only when one of the println, printf, or format methods is invoked, rather than whenever a newline character happens to be output. These methods use the platform's own notion of line separator rather than the newline character.

Methods in this class never throw I/O exceptions, although some of its constructors may. The client may inquire as to whether any errors have occurred by invoking checkError().

This class always replaces malformed and unmappable character sequences with the charset's default replacement string. The CharsetEncoder class should be used when more control over the encoding process is required.

Since:
1.1

Field Summary

Modifier and Type Field Description
protected Writer out
The underlying character-output stream of this PrintWriter.

Fields declared in class java.io.Writer

lock

Constructor Summary

Constructor Description
PrintWriter(File file)
Creates a new PrintWriter, without automatic line flushing, with the specified file.
PrintWriter(File file, String csn)
Creates a new PrintWriter, without automatic line flushing, with the specified file and charset.
PrintWriter(File file, Charset charset)
Creates a new PrintWriter, without automatic line flushing, with the specified file and charset.
PrintWriter(OutputStream out)
Creates a new PrintWriter, without automatic line flushing, from an existing OutputStream.
PrintWriter(OutputStream out, boolean autoFlush)
Creates a new PrintWriter from an existing OutputStream.
PrintWriter(OutputStream out, boolean autoFlush, Charset charset)
Creates a new PrintWriter from an existing OutputStream.
PrintWriter(Writer out)
Creates a new PrintWriter, without automatic line flushing.
PrintWriter(Writer out, boolean autoFlush)
Creates a new PrintWriter.
PrintWriter(String fileName)
Creates a new PrintWriter, without automatic line flushing, with the specified file name.
PrintWriter(String fileName, String csn)
Creates a new PrintWriter, without automatic line flushing, with the specified file name and charset.
PrintWriter(String fileName, Charset charset)
Creates a new PrintWriter, without automatic line flushing, with the specified file name and charset.

Method Summary

Modifier and Type Method Description
PrintWriter append(char c)
Appends the specified character to this writer.
PrintWriter append(CharSequence csq)
Appends the specified character sequence to this writer.
PrintWriter append(CharSequence csq, int start, int end)
Appends a subsequence of the specified character sequence to this writer.
boolean checkError()
Flushes the stream if it's not closed and checks its error state.
protected void clearError()
Clears the error state of this stream.
void close()
Closes the stream and releases any system resources associated with it.
void flush()
Flushes the stream.
PrintWriter format(String format, Object... args)
Writes a formatted string to this writer using the specified format string and arguments.
PrintWriter format(Locale l, String format, Object... args)
Writes a formatted string to this writer using the specified format string and arguments.
void print(boolean b)
Prints a boolean value.
void print(char c)
Prints a character.
void print(char[] s)
Prints an array of characters.
void print(double d)
Prints a double-precision floating-point number.
void print(float f)
Prints a floating-point number.
void print(int i)
Prints an integer.
void print(long l)
Prints a long integer.
void print(Object obj)
Prints an object.
void print(String s)
Prints a string.
PrintWriter printf(String format, Object... args)
A convenience method to write a formatted string to this writer using the specified format string and arguments.
PrintWriter printf(Locale l, String format, Object... args)
A convenience method to write a formatted string to this writer using the specified format string and arguments.
void println()
Terminates the current line by writing the line separator string.
void println(boolean x)
Prints a boolean value and then terminates the line.
void println(char x)
Prints a character and then terminates the line.
void println(char[] x)
Prints an array of characters and then terminates the line.
void println(double x)
Prints a double-precision floating-point number and then terminates the line.
void println(float x)
Prints a floating-point number and then terminates the line.
void println(int x)
Prints an integer and then terminates the line.
void println(long x)
Prints a long integer and then terminates the line.
void println(Object x)
Prints an Object and then terminates the line.
void println(String x)
Prints a String and then terminates the line.
protected void setError()
Sets the error state of the stream to true.
void write(char[] buf)
Writes an array of characters.
void write(char[] buf, int off, int len)
Writes A Portion of an array of characters.
void write(int c)
Writes a single character.
void write(String s)
Writes a string.
void write(String s, int off, int len)
Writes a portion of a string.

Methods declared in class java.io.Writer

nullWriter

Methods declared in class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Details

out

protected Writer out
The underlying character-output stream of this PrintWriter.
Since:
1.2

Constructor Details

PrintWriter

public PrintWriter(Writer out)
Creates a new PrintWriter, without automatic line flushing.
Parameters:
out - A character-output stream

PrintWriter

public PrintWriter(Writer out, boolean autoFlush)
Creates a new PrintWriter.
Parameters:
out - A character-output stream
autoFlush - A boolean; if true, the println, printf, or format methods will flush the output buffer

PrintWriter

public PrintWriter(OutputStream out)
Creates a new PrintWriter, without automatic line flushing, from an existing OutputStream. This convenience constructor creates the necessary intermediate OutputStreamWriter, which will convert characters into bytes using the default charset, or where out is a PrintStream, the charset used by the print stream.
Parameters:
out - An output stream
See Also:

PrintWriter

public PrintWriter(OutputStream out, boolean autoFlush)
Creates a new PrintWriter from an existing OutputStream. This convenience constructor creates the necessary intermediate OutputStreamWriter, which will convert characters into bytes using the default charset, or where out is a PrintStream, the charset used by the print stream.
Parameters:
out - An output stream
autoFlush - A boolean; if true, the println, printf, or format methods will flush the output buffer
See Also:

PrintWriter

public PrintWriter(OutputStream out, boolean autoFlush, Charset charset)
Creates a new PrintWriter from an existing OutputStream. This convenience constructor creates the necessary intermediate OutputStreamWriter, which will convert characters into bytes using the specified charset.
Parameters:
out - An output stream
autoFlush - A boolean; if true, the println, printf, or format methods will flush the output buffer
charset - A charset
Since:
10

PrintWriter

public PrintWriter(String fileName) throws FileNotFoundException
Creates a new PrintWriter, without automatic line flushing, with the specified file name. This convenience constructor creates the necessary intermediate OutputStreamWriter, which will encode characters using the default charset for this instance of the Java virtual machine.
Parameters:
fileName - The name of the file to use as the destination of this writer. If the file exists then it will be truncated to zero size; otherwise, a new file will be created. The output will be written to the file and is buffered.
Throws:
FileNotFoundException - If the given string does not denote an existing, writable regular file and a new regular file of that name cannot be created, or if some other error occurs while opening or creating the file
SecurityException - If a security manager is present and checkWrite(fileName) denies write access to the file
Since:
1.5
See Also:

PrintWriter

public PrintWriter(String fileName, String csn) throws FileNotFoundException, UnsupportedEncodingException
Creates a new PrintWriter, without automatic line flushing, with the specified file name and charset. This convenience constructor creates the necessary intermediate OutputStreamWriter, which will encode characters using the provided charset.
Parameters:
fileName - The name of the file to use as the destination of this writer. If the file exists then it will be truncated to zero size; otherwise, a new file will be created. The output will be written to the file and is buffered.
csn - The name of a supported charset
Throws:
FileNotFoundException - If the given string does not denote an existing, writable regular file and a new regular file of that name cannot be created, or if some other error occurs while opening or creating the file
SecurityException - If a security manager is present and checkWrite(fileName) denies write access to the file
UnsupportedEncodingException - If the named charset is not supported
Since:
1.5

PrintWriter

public PrintWriter(String fileName, Charset charset) throws IOException
Creates a new PrintWriter, without automatic line flushing, with the specified file name and charset. This convenience constructor creates the necessary intermediate OutputStreamWriter, which will encode characters using the provided charset.
Parameters:
fileName - The name of the file to use as the destination of this writer. If the file exists then it will be truncated to zero size; otherwise, a new file will be created. The output will be written to the file and is buffered.
charset - A charset
Throws:
IOException - if an I/O error occurs while opening or creating the file
SecurityException - If a security manager is present and checkWrite(fileName) denies write access to the file
Since:
10

PrintWriter

public PrintWriter(File file) throws FileNotFoundException
Creates a new PrintWriter, without automatic line flushing, with the specified file. This convenience constructor creates the necessary intermediate OutputStreamWriter, which will encode characters using the default charset for this instance of the Java virtual machine.
Parameters:
file - The file to use as the destination of this writer. If the file exists then it will be truncated to zero size; otherwise, a new file will be created. The output will be written to the file and is buffered.
Throws:
FileNotFoundException - If the given file object does not denote an existing, writable regular file and a new regular file of that name cannot be created, or if some other error occurs while opening or creating the file
SecurityException - If a security manager is present and checkWrite(file.getPath()) denies write access to the file
Since:
1.5
See Also:

PrintWriter

public PrintWriter(File file, String csn) throws FileNotFoundException, UnsupportedEncodingException
Creates a new PrintWriter, without automatic line flushing, with the specified file and charset. This convenience constructor creates the necessary intermediate OutputStreamWriter, which will encode characters using the provided charset.
Parameters:
file - The file to use as the destination of this writer. If the file exists then it will be truncated to zero size; otherwise, a new file will be created. The output will be written to the file and is buffered.
csn - The name of a supported charset
Throws:
FileNotFoundException - If the given file object does not denote an existing, writable regular file and a new regular file of that name cannot be created, or if some other error occurs while opening or creating the file
SecurityException - If a security manager is present and checkWrite(file.getPath()) denies write access to the file
UnsupportedEncodingException - If the named charset is not supported
Since:
1.5

PrintWriter

public PrintWriter(File file, Charset charset) throws IOException
Creates a new PrintWriter, without automatic line flushing, with the specified file and charset. This convenience constructor creates the necessary intermediate OutputStreamWriter, which will encode characters using the provided charset.
Parameters:
file - The file to use as the destination of this writer. If the file exists then it will be truncated to zero size; otherwise, a new file will be created. The output will be written to the file and is buffered.
charset - A charset
Throws:
IOException - if an I/O error occurs while opening or creating the file
SecurityException - If a security manager is present and checkWrite(file.getPath()) denies write access to the file
Since:
10

Method Details

flush

public void flush()
Flushes the stream.
Specified by:
flush in interface Flushable
Specified by:
flush in class Writer
See Also:

close

public void close()
Closes the stream and releases any system resources associated with it. Closing a previously closed stream has no effect.
Specified by:
close in interface AutoCloseable
Specified by:
close in interface Closeable
Specified by:
close in class Writer
See Also:

checkError

public boolean checkError()
Flushes the stream if it's not closed and checks its error state.
Returns:
true if and only if this stream has encountered an IOException, or the setError method has been invoked

setError

protected void setError()
Sets the error state of the stream to true.

This method will cause subsequent invocations of checkError() to return true until clearError() is invoked.

clearError

protected void clearError()
Clears the error state of this stream.

This method will cause subsequent invocations of checkError() to return false until another write operation fails and invokes setError().

Since:
1.6

write

public void write(int c)
Writes a single character.
Overrides:
write in class Writer
Parameters:
c - int specifying a character to be written.

write

public void write(char[] buf, int off, int len)
Writes A Portion of an array of characters.
Specified by:
write in class Writer
Parameters:
buf - Array of characters
off - Offset from which to start writing characters
len - Number of characters to write
Throws:
IndexOutOfBoundsException - If the values of the off and len parameters cause the corresponding method of the underlying Writer to throw an IndexOutOfBoundsException

write

public void write(char[] buf)
Writes an array of characters. This method cannot be inherited from the Writer class because it must suppress I/O exceptions.
Overrides:
write in class Writer
Parameters:
buf - Array of characters to be written

write

public void write(String s, int off, int len)
Writes a portion of a string.
Overrides:
write in class Writer
Parameters:
s - A String
off - Offset from which to start writing characters
len - Number of characters to write
Throws:
IndexOutOfBoundsException - If the values of the off and len parameters cause the corresponding method of the underlying Writer to throw an IndexOutOfBoundsException

write

public void write(String s)
Writes a string. This method cannot be inherited from the Writer class because it must suppress I/O exceptions.
Overrides:
write in class Writer
Parameters:
s - String to be written

print

public void print(boolean b)
Prints a boolean value. The string produced by String.valueOf(boolean) is translated into bytes according to the default charset, and these bytes are written in exactly the manner of the write(int) method.
Parameters:
b - The boolean to be printed
See Also:

print

public void print(char c)
Prints a character. The character is translated into one or more bytes according to the default charset, and these bytes are written in exactly the manner of the write(int) method.
Parameters:
c - The char to be printed
See Also:

print

public void print(int i)
Prints an integer. The string produced by String.valueOf(int) is translated into bytes according to the default charset, and these bytes are written in exactly the manner of the write(int) method.
Parameters:
i - The int to be printed
See Also:

print

public void print(long l)
Prints a long integer. The string produced by String.valueOf(long) is translated into bytes according to the default charset, and these bytes are written in exactly the manner of the write(int) method.
Parameters:
l - The long to be printed
See Also:

print

public void print(float f)
Prints a floating-point number. The string produced by String.valueOf(float) is translated into bytes according to the default charset, and these bytes are written in exactly the manner of the write(int) method.
Parameters:
f - The float to be printed
See Also:

print

public void print(double d)
Prints a double-precision floating-point number. The string produced by String.valueOf(double) is translated into bytes according to the default charset, and these bytes are written in exactly the manner of the write(int) method.
Parameters:
d - The double to be printed
See Also:

print

public void print(char[] s)
Prints an array of characters. The characters are converted into bytes according to the default charset, and these bytes are written in exactly the manner of the write(int) method.
Parameters:
s - The array of chars to be printed
Throws:
NullPointerException - If s is null
See Also:

print

public void print(String s)
Prints a string. If the argument is null then the string "null" is printed. Otherwise, the string's characters are converted into bytes according to the default charset, and these bytes are written in exactly the manner of the write(int) method.
Parameters:
s - The String to be printed
See Also:

print

public void print(Object obj)
Prints an object. The string produced by the String.valueOf(Object) method is translated into bytes according to the default charset, and these bytes are written in exactly the manner of the write(int) method.
Parameters:
obj - The Object to be printed
See Also:

println

public void println()
Terminates the current line by writing the line separator string. The line separator is System.lineSeparator() and is not necessarily a single newline character ('\n').

println

public void println(boolean x)
Prints a boolean value and then terminates the line. This method behaves as though it invokes print(boolean) and then println().
Parameters:
x - the boolean value to be printed

println

public void println(char x)
Prints a character and then terminates the line. This method behaves as though it invokes print(char) and then println().
Parameters:
x - the char value to be printed

println

public void println(int x)
Prints an integer and then terminates the line. This method behaves as though it invokes print(int) and then println().
Parameters:
x - the int value to be printed

println

public void println(long x)
Prints a long integer and then terminates the line. This method behaves as though it invokes print(long) and then println().
Parameters:
x - the long value to be printed

println

public void println(float x)
Prints a floating-point number and then terminates the line. This method behaves as though it invokes print(float) and then println().
Parameters:
x - the float value to be printed

println

public void println(double x)
Prints a double-precision floating-point number and then terminates the line. This method behaves as though it invokes print(double) and then println().
Parameters:
x - the double value to be printed

println

public void println(char[] x)
Prints an array of characters and then terminates the line. This method behaves as though it invokes print(char[]) and then println().
Parameters:
x - the array of char values to be printed

println

public void println(String x)
Prints a String and then terminates the line. This method behaves as though it invokes print(String) and then println().
Parameters:
x - the String value to be printed

println

public void println(Object x)
Prints an Object and then terminates the line. This method calls at first String.valueOf(x) to get the printed object's string value, then behaves as though it invokes print(String) and then println().
Parameters:
x - The Object to be printed.

printf

public PrintWriter printf(String format, Object... args)
A convenience method to write a formatted string to this writer using the specified format string and arguments. If automatic flushing is enabled, calls to this method will flush the output buffer.

An invocation of this method of the form out.printf(format, args) behaves in exactly the same way as the invocation 

    out.format(format, args)
Parameters:
format - A format string as described in Format string syntax.
args - Arguments referenced by the format specifiers in the format string. If there are more arguments than format specifiers, the extra arguments are ignored. The number of arguments is variable and may be zero. The maximum number of arguments is limited by the maximum dimension of a Java array as defined by The Java Virtual Machine Specification. The behaviour on a null argument depends on the conversion.
Returns:
This writer
Throws:
IllegalFormatException - If a format string contains an illegal syntax, a format specifier that is incompatible with the given arguments, insufficient arguments given the format string, or other illegal conditions. For specification of all possible formatting errors, see the Details section of the formatter class specification.
NullPointerException - If the format is null
Since:
1.5

printf

public PrintWriter printf(Locale l, String format, Object... args)
A convenience method to write a formatted string to this writer using the specified format string and arguments. If automatic flushing is enabled, calls to this method will flush the output buffer.

An invocation of this method of the form out.printf(l, format, args) behaves in exactly the same way as the invocation 

    out.format(l, format, args)
Parameters:
l - The locale to apply during formatting. If l is null then no localization is applied.
format - A format string as described in Format string syntax.
args - Arguments referenced by the format specifiers in the format string. If there are more arguments than format specifiers, the extra arguments are ignored. The number of arguments is variable and may be zero. The maximum number of arguments is limited by the maximum dimension of a Java array as defined by The Java Virtual Machine Specification. The behaviour on a null argument depends on the conversion.
Returns:
This writer
Throws:
IllegalFormatException - If a format string contains an illegal syntax, a format specifier that is incompatible with the given arguments, insufficient arguments given the format string, or other illegal conditions. For specification of all possible formatting errors, see the Details section of the formatter class specification.
NullPointerException - If the format is null
Since:
1.5

format

public PrintWriter format(String format, Object... args)
Writes a formatted string to this writer using the specified format string and arguments. If automatic flushing is enabled, calls to this method will flush the output buffer.

The locale always used is the one returned by Locale.getDefault(), regardless of any previous invocations of other formatting methods on this object.

Parameters:
format - A format string as described in Format string syntax.
args - Arguments referenced by the format specifiers in the format string. If there are more arguments than format specifiers, the extra arguments are ignored. The number of arguments is variable and may be zero. The maximum number of arguments is limited by the maximum dimension of a Java array as defined by The Java Virtual Machine Specification. The behaviour on a null argument depends on the conversion.
Returns:
This writer
Throws:
IllegalFormatException - If a format string contains an illegal syntax, a format specifier that is incompatible with the given arguments, insufficient arguments given the format string, or other illegal conditions. For specification of all possible formatting errors, see the Details section of the Formatter class specification.
NullPointerException - If the format is null
Since:
1.5

format

public PrintWriter format(Locale l, String format, Object... args)
Writes a formatted string to this writer using the specified format string and arguments. If automatic flushing is enabled, calls to this method will flush the output buffer.
Parameters:
l - The locale to apply during formatting. If l is null then no localization is applied.
format - A format string as described in Format string syntax.
args - Arguments referenced by the format specifiers in the format string. If there are more arguments than format specifiers, the extra arguments are ignored. The number of arguments is variable and may be zero. The maximum number of arguments is limited by the maximum dimension of a Java array as defined by The Java Virtual Machine Specification. The behaviour on a null argument depends on the conversion.
Returns:
This writer
Throws:
IllegalFormatException - If a format string contains an illegal syntax, a format specifier that is incompatible with the given arguments, insufficient arguments given the format string, or other illegal conditions. For specification of all possible formatting errors, see the Details section of the formatter class specification.
NullPointerException - If the format is null
Since:
1.5

append

public PrintWriter append(CharSequence csq)
Appends the specified character sequence to this writer.

An invocation of this method of the form out.append(csq) behaves in exactly the same way as the invocation 

    out.write(csq.toString())

Depending on the specification of toString for the character sequence csq, the entire sequence may not be appended. For instance, invoking the toString method of a character buffer will return a subsequence whose content depends upon the buffer's position and limit.

Specified by:
append in interface Appendable
Overrides:
append in class Writer
Parameters:
csq - The character sequence to append. If csq is null, then the four characters "null" are appended to this writer.
Returns:
This writer
Since:
1.5

append

public PrintWriter append(CharSequence csq, int start, int end)
Appends a subsequence of the specified character sequence to this writer.

An invocation of this method of the form out.append(csq, start, end) when csq is not null, behaves in exactly the same way as the invocation 

    out.write(csq.subSequence(start, end).toString())
Specified by:
append in interface Appendable
Overrides:
append in class Writer
Parameters:
csq - The character sequence from which a subsequence will be appended. If csq is null, then characters will be appended as if csq contained the four characters "null".
start - The index of the first character in the subsequence
end - The index of the character following the last character in the subsequence
Returns:
This writer
Throws:
IndexOutOfBoundsException - If start or end are negative, start is greater than end, or end is greater than csq.length()
Since:
1.5

append

public PrintWriter append(char c)
Appends the specified character to this writer.

An invocation of this method of the form out.append(c) behaves in exactly the same way as the invocation 

    out.write(c)
Specified by:
append in interface Appendable
Overrides:
append in class Writer
Parameters:
c - The 16-bit character to append
Returns:
This writer
Since:
1.5

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Documentation extracted from Debian's OpenJDK Development Kit package.
Licensed under the GNU General Public License, version 2, with the Classpath Exception.
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https://docs.oracle.com/en/java/javase/21/docs/api/java.base/java/io/PrintWriter.html