Objects | API reference | Android Developers

public final class Objects
extends Object

This class consists of 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.

Summary

Public methods
`static long`	`checkFromIndexSize(long fromIndex, long size, long length)` 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`	`checkFromIndexSize(int fromIndex, int size, int length)` 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(int fromIndex, int toIndex, int length)` 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(long fromIndex, long toIndex, long length)` 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`	`checkIndex(long index, long length)` Checks if the `index` is within the bounds of the range from `0` (inclusive) to `length` (exclusive).
`static int`	`checkIndex(int index, int length)` Checks if the `index` is within the bounds of the range from `0` (inclusive) to `length` (exclusive).
`static <T> int`	`compare(T a, T b, Comparator<? super T> c)` Returns 0 if the arguments are identical and `c.compare(a, b)` otherwise.
`static boolean`	`deepEquals(Object a, Object b)` Returns `true` if the arguments are deeply equal to each other and `false` otherwise.
`static boolean`	`equals(Object a, Object b)` Returns `true` if the arguments are equal to each other and `false` otherwise.
`static int`	`hash(Object... values)` Generates a hash code for a sequence of input values.
`static int`	`hashCode(Object o)` Returns the hash code of a non-`null` argument and 0 for a `null` argument.
`static boolean`	`isNull(Object obj)` Returns `true` if the provided reference is `null` otherwise returns `false`.
`static boolean`	`nonNull(Object obj)` Returns `true` if the provided reference is non-`null` otherwise returns `false`.
`static <T> T`	`requireNonNull(T obj, String message)` Checks that the specified object reference is not `null` and throws a customized `NullPointerException` if it is.
`static <T> T`	`requireNonNull(T obj, Supplier<String> messageSupplier)` Checks that the specified object reference is not `null` and throws a customized `NullPointerException` if it is.
`static <T> T`	`requireNonNull(T obj)` Checks that the specified object reference is not `null`.
`static <T> T`	`requireNonNullElse(T obj, T defaultObj)` Returns the first argument if it is non-`null` and otherwise returns the non-`null` second argument.
`static <T> T`	`requireNonNullElseGet(T obj, Supplier<? extends T> supplier)` Returns the first argument if it is non-`null` and otherwise returns the non-`null` value of `supplier.get()`.
`static String`	`toIdentityString(Object o)`
`static String`	`toString(Object o)` Returns the result of calling `toString` for a non-`null` argument and `"null"` for a `null` argument.
`static String`	`toString(Object o, String nullDefault)` Returns the result of calling `toString` on the first argument if the first argument is not `null` and returns the second argument otherwise.

Inherited methods

From class java.lang.Object

`Object`	`clone()` Creates and returns a copy of this object.
`boolean`	`equals(Object obj)` Indicates whether some other object is "equal to" this one.
`void`	`finalize()` Called by the garbage collector on an object when garbage collection determines that there are no more references to the object.
`final Class<?>`	`getClass()` Returns the runtime class of this `Object`.
`int`	`hashCode()` Returns a hash code value for the object.
`final void`	`notify()` Wakes up a single thread that is waiting on this object's monitor.
`final void`	`notifyAll()` Wakes up all threads that are waiting on this object's monitor.
`String`	`toString()` Returns a string representation of the object.
`final void`	`wait(long timeoutMillis, int nanos)` Causes the current thread to wait until it is awakened, typically by being notified or interrupted, or until a certain amount of real time has elapsed.
`final void`	`wait(long timeoutMillis)` Causes the current thread to wait until it is awakened, typically by being notified or interrupted, or until a certain amount of real time has elapsed.
`final void`	`wait()` Causes the current thread to wait until it is awakened, typically by being notified or interrupted.

Public methods

checkFromIndexSize

public static long checkFromIndexSize (long fromIndex, 
                long size, 
                long length)

Checks if the sub-range from 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 overflow
length < 0, which is implied from the former inequalities

Parameters
`fromIndex`	`long`: the lower-bound (inclusive) of the sub-interval
`size`	`long`: the size of the sub-range
`length`	`long`: the upper-bound (exclusive) of the range

Returns
`long`	`fromIndex` if the sub-range within bounds of the range

Throws
`IndexOutOfBoundsException`	if the sub-range is out of bounds

checkFromIndexSize

public static int checkFromIndexSize (int fromIndex, 
                int size, 
                int length)

Checks if the sub-range from 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 overflow
length < 0, which is implied from the former inequalities

Parameters
`fromIndex`	`int`: the lower-bound (inclusive) of the sub-interval
`size`	`int`: the size of the sub-range
`length`	`int`: the upper-bound (exclusive) of the range

Returns
`int`	`fromIndex` if the sub-range within bounds of the range

Throws
`IndexOutOfBoundsException`	if the sub-range is out of bounds

checkFromToIndex

public static int checkFromToIndex (int fromIndex, 
                int toIndex, 
                int length)

Checks if the sub-range from 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 inequalities

Parameters
`fromIndex`	`int`: the lower-bound (inclusive) of the sub-range
`toIndex`	`int`: the upper-bound (exclusive) of the sub-range
`length`	`int`: the upper-bound (exclusive) the range

Returns
`int`	`fromIndex` if the sub-range within bounds of the range

Throws
`IndexOutOfBoundsException`	if the sub-range is out of bounds

checkFromToIndex

public static long checkFromToIndex (long fromIndex, 
                long toIndex, 
                long length)

Checks if the sub-range from 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 inequalities

Parameters
`fromIndex`	`long`: the lower-bound (inclusive) of the sub-range
`toIndex`	`long`: the upper-bound (exclusive) of the sub-range
`length`	`long`: the upper-bound (exclusive) the range

Returns
`long`	`fromIndex` if the sub-range within bounds of the range

Throws
`IndexOutOfBoundsException`	if the sub-range is out of bounds

checkIndex

public static long checkIndex (long index, 
                long length)

Checks if the 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 inequalities

Parameters
`index`	`long`: the index
`length`	`long`: the upper-bound (exclusive) of the range

Returns
`long`	`index` if it is within bounds of the range

Throws
`IndexOutOfBoundsException`	if the `index` is out of bounds

checkIndex

public static int checkIndex (int index, 
                int length)

Checks if the 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 inequalities

Parameters
`index`	`int`: the index
`length`	`int`: the upper-bound (exclusive) of the range

Returns
`int`	`index` if it is within bounds of the range

Throws
`IndexOutOfBoundsException`	if the `index` is out of bounds

compare

public static int compare (T a, 
                T b, 
                Comparator<? super T> c)

Returns 0 if the arguments are identical and 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.

Parameters
`a`	`T`: an object
`b`	`T`: an object to be compared with `a`
`c`	`Comparator`: the `Comparator` to compare the first two arguments

Returns
`int`	0 if the arguments are identical and `c.compare(a, b)` otherwise.

deepEquals

public static boolean deepEquals (Object a, 
                Object b)

Returns 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.

Parameters
`a`	`Object`: an object
`b`	`Object`: an object to be compared with `a` for deep equality

Returns
`boolean`	`true` if the arguments are deeply equal to each other and `false` otherwise

equals

public static boolean equals (Object a, 
                Object b)

Returns 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.

Parameters
`a`	`Object`: an object
`b`	`Object`: an object to be compared with `a` for equality

Returns
`boolean`	`true` if the arguments are equal to each other and `false` otherwise

hash

public static int hash (Object... values)

Generates a hash code for a sequence of input values. The hash code is generated as if all the input values were placed into an array, and that array were hashed by calling 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:

 @Override public int hashCode() {
     return Objects.hash(x, y, z);
 }

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 hashCode(Object).

Parameters
`values`	`Object`: the values to be hashed

Returns
`int`	a hash value of the sequence of input values

hashCode

public static int hashCode (Object o)

Returns the hash code of a non-null argument and 0 for a null argument.

Parameters
`o`	`Object`: an object

Returns
`int`	the hash code of a non-`null` argument and 0 for a `null` argument

isNull

public static boolean isNull (Object obj)

Returns true if the provided reference is null otherwise returns false.

API Note:

This method exists to be used as a Predicate, filter(Objects::isNull)

Parameters
`obj`	`Object`: a reference to be checked against `null`

Returns
`boolean`	`true` if the provided reference is `null` otherwise `false`

nonNull

public static boolean nonNull (Object obj)

Returns true if the provided reference is non-null otherwise returns false.

API Note:

This method exists to be used as a Predicate, filter(Objects::nonNull)

Parameters
`obj`	`Object`: a reference to be checked against `null`

Returns
`boolean`	`true` if the provided reference is non-`null` otherwise `false`

requireNonNull

public static T requireNonNull (T obj, 
                String message)

Checks that the specified object reference is not 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");
 }

Parameters
`obj`	`T`: the object reference to check for nullity
`message`	`String`: detail message to be used in the event that a `NullPointerException` is thrown

Returns
`T`	`obj` if not `null`

Throws
`NullPointerException`	if `obj` is `null`

requireNonNull

public static T requireNonNull (T obj, 
                Supplier<String> messageSupplier)

Checks that the specified object reference is not 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.

Parameters
`obj`	`T`: the object reference to check for nullity
`messageSupplier`	`Supplier`: supplier of the detail message to be used in the event that a `NullPointerException` is thrown

Returns
`T`	`obj` if not `null`

Throws
`NullPointerException`	if `obj` is `null`

requireNonNull

public static T requireNonNull (T obj)

Checks that the specified object reference is not 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);
 }

Parameters
`obj`	`T`: the object reference to check for nullity

Returns
`T`	`obj` if not `null`

Throws
`NullPointerException`	if `obj` is `null`

requireNonNullElse

public static T requireNonNullElse (T obj, 
                T defaultObj)

Returns the first argument if it is non-null and otherwise returns the non-null second argument.

Parameters
`obj`	`T`: an object
`defaultObj`	`T`: a non-`null` object to return if the first argument is `null`

Returns
`T`	the first argument if it is non-`null` and otherwise the second argument if it is non-`null`

Throws
`NullPointerException`	if both `obj` is null and `defaultObj` is `null`

requireNonNullElseGet

public static T requireNonNullElseGet (T obj, 
                Supplier<? extends T> supplier)

Returns the first argument if it is non-null and otherwise returns the non-null value of supplier.get().

Parameters
`obj`	`T`: an object
`supplier`	`Supplier`: of a non-`null` object to return if the first argument is `null`

Returns
`T`	the first argument if it is non-`null` and otherwise the value from `supplier.get()` if it is non-`null`

Throws
`NullPointerException`	if both `obj` is null and either the `supplier` is `null` or the `supplier.get()` value is `null`

toIdentityString

public static String toIdentityString (Object o)

Implementation Note:

This method constructs a string for an object without calling any overridable methods of the object.

Implementation Requirements:

The method returns a string equivalent to:
o.getClass().getName() + "@" + Integer.toHexString(System.identityHashCode(o))

Parameters
`o`	`Object`: an object

Returns
`String`	a string equivalent to the string returned by `Object.toString` if that method and `hashCode` are not overridden

Throws
`NullPointerException`	if the argument is null

toString

public static String toString (Object o)

Returns the result of calling toString for a non-null argument and "null" for a null argument.

Parameters
`o`	`Object`: an object

Returns
`String`	the result of calling `toString` for a non-`null` argument and `"null"` for a `null` argument

toString

public static String toString (Object o, 
                String nullDefault)

Returns the result of calling toString on the first argument if the first argument is not null and returns the second argument otherwise.

Parameters
`o`	`Object`: an object
`nullDefault`	`String`: string to return if the first argument is `null`

Returns
`String`	the result of calling `toString` on the first argument if it is not `null` and the second argument otherwise.