* #### equals
public static boolean equals([Object](../../java/lang/Object.html "class in java.lang") a,
[Object](../../java/lang/Object.html "class in java.lang") b)
Returns `true` if the arguments are equal to each other and `false` otherwise. Consequently, if both arguments are `null`, `true` is returned and if exactly one argument is `null`, ` false` is returned. Otherwise, equality is determined by using the [equals](../../java/lang/Object.html#equals-java.lang.Object-) method of the first argument.
Parameters:
`a` \- an object
`b` \- an object to be compared with `a` for equality
Returns:
`true` if the arguments are equal to each other and `false` otherwise
See Also:
[Object.equals(Object)](../../java/lang/Object.html#equals-java.lang.Object-)
* #### deepEquals
public static boolean deepEquals([Object](../../java/lang/Object.html "class in java.lang") a,
[Object](../../java/lang/Object.html "class in java.lang") 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](../../java/util/Arrays.html#deepEquals-java.lang.Object:A-java.lang.Object:A-) is used to determine equality. Otherwise, equality is determined by using the [equals](../../java/lang/Object.html#equals-java.lang.Object-) method of the first argument.
Parameters:
`a` \- an object
`b` \- an object to be compared with `a` for deep equality
Returns:
`true` if the arguments are deeply equal to each other and `false` otherwise
See Also:
[Arrays.deepEquals(Object\[\], Object\[\])](../../java/util/Arrays.html#deepEquals-java.lang.Object:A-java.lang.Object:A-), [equals(Object, Object)](../../java/util/Objects.html#equals-java.lang.Object-java.lang.Object-)
* #### hashCode
public static int hashCode([Object](../../java/lang/Object.html "class in java.lang") o)
Returns the hash code of a non-`null` argument and 0 for a `null` argument.
Parameters:
`o` \- an object
Returns:
the hash code of a non-`null` argument and 0 for a `null` argument
See Also:
[Object.hashCode()](../../java/lang/Object.html#hashCode--)
* #### hash
public static int hash([Object](../../java/lang/Object.html "class in java.lang")... 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\[\])](../../java/util/Arrays.html#hashCode-java.lang.Object:A-).
This method is useful for implementing [Object.hashCode()](../../java/lang/Object.html#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)](../../java/util/Objects.html#hashCode-java.lang.Object-).
Parameters:
`values` \- the values to be hashed
Returns:
a hash value of the sequence of input values
See Also:
[Arrays.hashCode(Object\[\])](../../java/util/Arrays.html#hashCode-java.lang.Object:A-), [List.hashCode()](../../java/util/List.html#hashCode--)
* #### toString
public static [String](../../java/lang/String.html "class in java.lang") toString([Object](../../java/lang/Object.html "class in java.lang") o)
Returns the result of calling `toString` for a non-` null` argument and `"null"` for a `null` argument.
Parameters:
`o` \- an object
Returns:
the result of calling `toString` for a non-` null` argument and `"null"` for a `null` argument
See Also:
[Object.toString()](../../java/lang/Object.html#toString--), [String.valueOf(Object)](../../java/lang/String.html#valueOf-java.lang.Object-)
* #### toString
public static [String](../../java/lang/String.html "class in java.lang") toString([Object](../../java/lang/Object.html "class in java.lang") o,
[String](../../java/lang/String.html "class in java.lang") 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` \- an object
`nullDefault` \- string to return if the first argument is`null`
Returns:
the result of calling `toString` on the first argument if it is not `null` and the second argument otherwise.
See Also:
[toString(Object)](../../java/util/Objects.html#toString-java.lang.Object-)
* #### compare
public static <T> int compare(T a,
T b,
[Comparator](../../java/util/Comparator.html "interface in java.util")<? 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](../../java/util/Comparator.html "interface in java.util") chooses to have for `null` values.
Type Parameters:
`T` \- the type of the objects being compared
Parameters:
`a` \- an object
`b` \- an object to be compared with `a`
`c` \- the `Comparator` to compare the first two arguments
Returns:
0 if the arguments are identical and ` c.compare(a, b)` otherwise.
See Also:
[Comparable](../../java/lang/Comparable.html "interface in java.lang"), [Comparator](../../java/util/Comparator.html "interface in java.util")
* #### requireNonNull
public static <T> 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);
> }
>
Type Parameters:
`T` \- the type of the reference
Parameters:
`obj` \- the object reference to check for nullity
Returns:
`obj` if not `null`
Throws:
`[NullPointerException](../../java/lang/NullPointerException.html "class in java.lang")` \- if `obj` is `null`
* #### requireNonNull
public static <T> T requireNonNull(T obj,
[String](../../java/lang/String.html "class in java.lang") message)
Checks that the specified object reference is not `null` and throws a customized [NullPointerException](../../java/lang/NullPointerException.html "class in java.lang") 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");
> }
>
Type Parameters:
`T` \- the type of the reference
Parameters:
`obj` \- the object reference to check for nullity
`message` \- detail message to be used in the event that a ` NullPointerException` is thrown
Returns:
`obj` if not `null`
Throws:
`[NullPointerException](../../java/lang/NullPointerException.html "class in java.lang")` \- if `obj` is `null`
* #### isNull
public static boolean isNull([Object](../../java/lang/Object.html "class in java.lang") obj)
Returns `true` if the provided reference is `null` otherwise returns `false`.
API Note:
This method exists to be used as a[Predicate](../../java/util/function/Predicate.html "interface in java.util.function"), `filter(Objects::isNull)`
Parameters:
`obj` \- a reference to be checked against `null`
Returns:
`true` if the provided reference is `null` otherwise`false`
Since:
1.8
See Also:
[Predicate](../../java/util/function/Predicate.html "interface in java.util.function")
* #### nonNull
public static boolean nonNull([Object](../../java/lang/Object.html "class in java.lang") obj)
Returns `true` if the provided reference is non-`null` otherwise returns `false`.
API Note:
This method exists to be used as a[Predicate](../../java/util/function/Predicate.html "interface in java.util.function"), `filter(Objects::nonNull)`
Parameters:
`obj` \- a reference to be checked against `null`
Returns:
`true` if the provided reference is non-`null` otherwise `false`
Since:
1.8
See Also:
[Predicate](../../java/util/function/Predicate.html "interface in java.util.function")
* #### requireNonNullElse
public 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.
Type Parameters:
`T` \- the type of the reference
Parameters:
`obj` \- an object
`defaultObj` \- a non-`null` object to return if the first argument is `null`
Returns:
the first argument if it is non-`null` and otherwise the second argument if it is non-`null`
Throws:
`[NullPointerException](../../java/lang/NullPointerException.html "class in java.lang")` \- if both `obj` is null and`defaultObj` is `null`
Since:
9
* #### requireNonNullElseGet
public static <T> T requireNonNullElseGet(T obj,
[Supplier](../../java/util/function/Supplier.html "interface in java.util.function")<? extends T> supplier)
Returns the first argument if it is non-`null` and otherwise returns the non-`null` value of `supplier.get()`.
Type Parameters:
`T` \- the type of the first argument and return type
Parameters:
`obj` \- an object
`supplier` \- of a non-`null` object to return if the first argument is `null`
Returns:
the first argument if it is non-`null` and otherwise the value from `supplier.get()` if it is non-`null`
Throws:
`[NullPointerException](../../java/lang/NullPointerException.html "class in java.lang")` \- if both `obj` is null and either the `supplier` is `null` or the `supplier.get()` value is `null`
Since:
9
* #### requireNonNull
public static <T> T requireNonNull(T obj,
[Supplier](../../java/util/function/Supplier.html "interface in java.util.function")<[String](../../java/lang/String.html "class in java.lang")> messageSupplier)
Checks that the specified object reference is not `null` and throws a customized [NullPointerException](../../java/lang/NullPointerException.html "class in java.lang") if it is.
Unlike the method [requireNonNull(Object, String)](../../java/util/Objects.html#requireNonNull-T-java.lang.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.
Type Parameters:
`T` \- the type of the reference
Parameters:
`obj` \- the object reference to check for nullity
`messageSupplier` \- supplier of the detail message to be used in the event that a `NullPointerException` is thrown
Returns:
`obj` if not `null`
Throws:
`[NullPointerException](../../java/lang/NullPointerException.html "class in java.lang")` \- if `obj` is `null`
Since:
1.8
* #### 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` \- the index
`length` \- the upper-bound (exclusive) of the range
Returns:
`index` if it is within bounds of the range
Throws:
`[IndexOutOfBoundsException](../../java/lang/IndexOutOfBoundsException.html "class in java.lang")` \- if the `index` is out-of-bounds
Since:
9
* #### 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` \- the lower-bound (inclusive) of the sub-range
`toIndex` \- the upper-bound (exclusive) of the sub-range
`length` \- the upper-bound (exclusive) the range
Returns:
`fromIndex` if the sub-range within bounds of the range
Throws:
`[IndexOutOfBoundsException](../../java/lang/IndexOutOfBoundsException.html "class in java.lang")` \- if the sub-range is out-of-bounds
Since:
9
* #### 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` \- the lower-bound (inclusive) of the sub-interval
`size` \- the size of the sub-range
`length` \- the upper-bound (exclusive) of the range
Returns:
`fromIndex` if the sub-range within bounds of the range
Throws:
`[IndexOutOfBoundsException](../../java/lang/IndexOutOfBoundsException.html "class in java.lang")` \- if the sub-range is out-of-bounds
Since:
9