Objects

public final class Objects extends Object

This class consists of static utility methods for operating on objects. These utilities include null-safe or null-tolerant methods for computing the hash code of an object, returning a string for an object, and comparing two objects.

Public Method Summary

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 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 Method Summary

Public Methods

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 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.

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 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

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 and if exactly one argument is null, false is returned. Otherwise, equality is determined by using the equals 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

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 hashCode(Object[]).

This method is useful for implementing 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 the values to be hashed
Returns
  • a hash value of the sequence of input values

public static int hashCode (Object 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