public final class Objects extends Object
static
utility methods for operating on objects, or checking certain conditions before operation. These utilities include null
-safe or null
-tolerant methods for computing the hash code of an object, returning a string for an object, comparing two objects, and checking if indexes or sub-range values are out of bounds.Modifier and Type | Method | Description |
---|---|---|
static int |
checkFromIndexSize |
Checks if the sub-range from fromIndex (inclusive) to fromIndex + size (exclusive) is within the bounds of range from 0 (inclusive) to length (exclusive). |
static long |
checkFromIndexSize |
Checks if the sub-range from fromIndex (inclusive) to fromIndex + size (exclusive) is within the bounds of range from 0 (inclusive) to length (exclusive). |
static int |
checkFromToIndex |
Checks if the sub-range from fromIndex (inclusive) to toIndex (exclusive) is within the bounds of range from 0 (inclusive) to length (exclusive). |
static long |
checkFromToIndex |
Checks if the sub-range from fromIndex (inclusive) to toIndex (exclusive) is within the bounds of range from 0 (inclusive) to length (exclusive). |
static int |
checkIndex |
Checks if the index is within the bounds of the range from 0 (inclusive) to length (exclusive). |
static long |
checkIndex |
Checks if the index is within the bounds of the range from 0 (inclusive) to length (exclusive). |
static <T> int |
compare |
Returns 0 if the arguments are identical and
c.compare(a, b) otherwise. |
static boolean |
deepEquals |
Returns true if the arguments are deeply equal to each other and false otherwise. |
static boolean |
equals |
Returns true if the arguments are equal to each other and false otherwise. |
static int |
hash |
Generates a hash code for a sequence of input values. |
static int |
hashCode |
Returns the hash code of a non- null argument and 0 for a null argument. |
static boolean |
isNull |
Returns true if the provided reference is null otherwise returns false . |
static boolean |
nonNull |
Returns true if the provided reference is non-null otherwise returns false . |
static <T> T |
requireNonNull |
Checks that the specified object reference is not null . |
static <T> T |
requireNonNull |
Checks that the specified object reference is not null and throws a customized NullPointerException if it is. |
static <T> T |
requireNonNull |
Checks that the specified object reference is not null and throws a customized NullPointerException if it is. |
static <T> T |
requireNonNullElse |
Returns the first argument if it is non- null and otherwise returns the non-null second argument. |
static <T> T |
requireNonNullElseGet |
Returns the first argument if it is non- null and otherwise returns the non-null value of supplier.get() . |
static String |
toIdentityString |
Returns a string equivalent to the string returned by
Object.toString if that method and hashCode are not overridden. |
static String |
toString |
Returns the result of calling toString for a non-
null argument and "null" for a null argument. |
static String |
toString |
Returns the result of calling toString on the first argument if the first argument is not null and returns the second argument otherwise. |
public static boolean equals(Object a, Object b)
true
if the arguments are equal to each other and false
otherwise. Consequently, if both arguments are null
, true
is returned. Otherwise, if the first argument is not
null
, equality is determined by calling the equals
method of the first argument with the second argument of this method. Otherwise, false
is returned.a
- an objectb
- an object to be compared with a
for equalitytrue
if the arguments are equal to each other and false
otherwisepublic static boolean deepEquals(Object a, Object b)
true
if the arguments are deeply equal to each other and false
otherwise. Two null
values are deeply equal. If both arguments are arrays, the algorithm in Arrays.deepEquals
is used to determine equality. Otherwise, equality is determined by using the equals
method of the first argument.a
- an objectb
- an object to be compared with a
for deep equalitytrue
if the arguments are deeply equal to each other and false
otherwisepublic static int hashCode(Object o)
null
argument and 0 for a null
argument.o
- an objectnull
argument and 0 for a null
argumentpublic static int hash(Object... values)
Arrays.hashCode(Object[])
. This method is useful for implementing Object.hashCode()
on objects containing multiple fields. For example, if an object that has three fields, x
,
y
, and z
, one could write:
Warning: When a single object reference is supplied, the returned value does not equal the hash code of that object reference. This value can be computed by calling@Override public int hashCode() { return Objects.hash(x, y, z); }
hashCode(Object)
.values
- the values to be hashedpublic static String toString(Object o)
toString
for a non-
null
argument and "null"
for a null
argument.o
- an objecttoString
for a non-
null
argument and "null"
for a null
argumentpublic static String toString(Object o, String nullDefault)
toString
on the first argument if the first argument is not null
and returns the second argument otherwise.o
- an objectnullDefault
- string to return if the first argument is null
toString
on the first argument if it is not null
and the second argument otherwise.public static String toIdentityString(Object o)
Object.toString
if that method and hashCode
are not overridden.o.getClass().getName() + "@" + Integer.toHexString(System.identityHashCode(o))
o
- an object
Object.toString
if that method and hashCode
are not overriddenNullPointerException
- if the argument is nullpublic static <T> int compare(T a, T b, Comparator<? super T> c)
c.compare(a, b)
otherwise. Consequently, if both arguments are null
0 is returned. Note that if one of the arguments is null
, a
NullPointerException
may or may not be thrown depending on what ordering policy, if any, the Comparator
chooses to have for null
values.
T
- the type of the objects being compareda
- an objectb
- an object to be compared with a
c
- the Comparator
to compare the first two arguments
c.compare(a, b)
otherwise.public static <T> T requireNonNull(T obj)
null
. This method is designed primarily for doing parameter validation in methods and constructors, as demonstrated below: public Foo(Bar bar) { this.bar = Objects.requireNonNull(bar); }
T
- the type of the referenceobj
- the object reference to check for nullityobj
if not null
NullPointerException
- if obj
is null
public static <T> T requireNonNull(T obj, String message)
null
and throws a customized NullPointerException
if it is. This method is designed primarily for doing parameter validation in methods and constructors with multiple parameters, as demonstrated below: public Foo(Bar bar, Baz baz) { this.bar = Objects.requireNonNull(bar, "bar must not be null"); this.baz = Objects.requireNonNull(baz, "baz must not be null"); }
T
- the type of the referenceobj
- the object reference to check for nullitymessage
- detail message to be used in the event that a
NullPointerException
is thrownobj
if not null
NullPointerException
- if obj
is null
public static boolean isNull(Object obj)
true
if the provided reference is null
otherwise returns false
.Predicate
, filter(Objects::isNull)
obj
- a reference to be checked against null
true
if the provided reference is null
otherwise false
public static boolean nonNull(Object obj)
true
if the provided reference is non-null
otherwise returns false
.Predicate
, filter(Objects::nonNull)
obj
- a reference to be checked against null
true
if the provided reference is non-null
otherwise false
public static <T> T requireNonNullElse(T obj, T defaultObj)
null
and otherwise returns the non-null
second argument.T
- the type of the referenceobj
- an objectdefaultObj
- a non-null
object to return if the first argument is null
null
and otherwise the second argument if it is non-null
NullPointerException
- if both obj
is null and defaultObj
is null
public static <T> T requireNonNullElseGet(T obj, Supplier<? extends T> supplier)
null
and otherwise returns the non-null
value of supplier.get()
.T
- the type of the first argument and return typeobj
- an objectsupplier
- of a non-null
object to return if the first argument is null
null
and otherwise the value from supplier.get()
if it is non-null
NullPointerException
- if both obj
is null and either the supplier
is null
or the supplier.get()
value is null
public static <T> T requireNonNull(T obj, Supplier<String> messageSupplier)
null
and throws a customized NullPointerException
if it is. Unlike the method requireNonNull(Object, String)
, this method allows creation of the message to be deferred until after the null check is made. While this may confer a performance advantage in the non-null case, when deciding to call this method care should be taken that the costs of creating the message supplier are less than the cost of just creating the string message directly.
T
- the type of the referenceobj
- the object reference to check for nullitymessageSupplier
- supplier of the detail message to be used in the event that a NullPointerException
is thrownobj
if not null
NullPointerException
- if obj
is null
public static int checkIndex(int index, int length)
index
is within the bounds of the range from 0
(inclusive) to length
(exclusive). The index
is defined to be out of bounds if any of the following inequalities is true:
index < 0
index >= length
length < 0
, which is implied from the former inequalitiesindex
- the indexlength
- the upper-bound (exclusive) of the rangeindex
if it is within bounds of the rangeIndexOutOfBoundsException
- if the index
is out of boundspublic static int checkFromToIndex(int fromIndex, int toIndex, int length)
fromIndex
(inclusive) to toIndex
(exclusive) is within the bounds of range from 0
(inclusive) to length
(exclusive). The sub-range is defined to be out of bounds if any of the following inequalities is true:
fromIndex < 0
fromIndex > toIndex
toIndex > length
length < 0
, which is implied from the former inequalitiesfromIndex
- the lower-bound (inclusive) of the sub-rangetoIndex
- the upper-bound (exclusive) of the sub-rangelength
- the upper-bound (exclusive) the rangefromIndex
if the sub-range within bounds of the rangeIndexOutOfBoundsException
- if the sub-range is out of boundspublic static int checkFromIndexSize(int fromIndex, int size, int length)
fromIndex
(inclusive) to fromIndex + size
(exclusive) is within the bounds of range from 0
(inclusive) to length
(exclusive). The sub-range is defined to be out of bounds if any of the following inequalities is true:
fromIndex < 0
size < 0
fromIndex + size > length
, taking into account integer overflowlength < 0
, which is implied from the former inequalitiesfromIndex
- the lower-bound (inclusive) of the sub-intervalsize
- the size of the sub-rangelength
- the upper-bound (exclusive) of the rangefromIndex
if the sub-range within bounds of the rangeIndexOutOfBoundsException
- if the sub-range is out of boundspublic static long checkIndex(long index, long length)
index
is within the bounds of the range from 0
(inclusive) to length
(exclusive). The index
is defined to be out of bounds if any of the following inequalities is true:
index < 0
index >= length
length < 0
, which is implied from the former inequalitiesindex
- the indexlength
- the upper-bound (exclusive) of the rangeindex
if it is within bounds of the rangeIndexOutOfBoundsException
- if the index
is out of boundspublic static long checkFromToIndex(long fromIndex, long toIndex, long length)
fromIndex
(inclusive) to toIndex
(exclusive) is within the bounds of range from 0
(inclusive) to length
(exclusive). The sub-range is defined to be out of bounds if any of the following inequalities is true:
fromIndex < 0
fromIndex > toIndex
toIndex > length
length < 0
, which is implied from the former inequalitiesfromIndex
- the lower-bound (inclusive) of the sub-rangetoIndex
- the upper-bound (exclusive) of the sub-rangelength
- the upper-bound (exclusive) the rangefromIndex
if the sub-range within bounds of the rangeIndexOutOfBoundsException
- if the sub-range is out of boundspublic static long checkFromIndexSize(long fromIndex, long size, long length)
fromIndex
(inclusive) to fromIndex + size
(exclusive) is within the bounds of range from 0
(inclusive) to length
(exclusive). The sub-range is defined to be out of bounds if any of the following inequalities is true:
fromIndex < 0
size < 0
fromIndex + size > length
, taking into account integer overflowlength < 0
, which is implied from the former inequalitiesfromIndex
- the lower-bound (inclusive) of the sub-intervalsize
- the size of the sub-rangelength
- the upper-bound (exclusive) of the rangefromIndex
if the sub-range within bounds of the rangeIndexOutOfBoundsException
- if the sub-range is out of bounds
© 1993, 2023, Oracle and/or its affiliates. All rights reserved.
Documentation extracted from Debian's OpenJDK Development Kit package.
Licensed under the GNU General Public License, version 2, with the Classpath Exception.
Various third party code in OpenJDK is licensed under different licenses (see Debian package).
Java and OpenJDK are trademarks or registered trademarks of Oracle and/or its affiliates.
https://docs.oracle.com/en/java/javase/21/docs/api/java.base/java/util/Objects.html