Class Objects

java.lang.Object
java.util.Objects
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.
Since:
1.7

  • Method Summary

    Modifier and Type
    Method
    Description
    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 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
    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 int
    checkIndex(int index, int length)
    Checks if the index is within the bounds of the 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 <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 long
    getObjectSize(Object o)
    Return the size of the object in the heap.
    static int
    hash(Object... values)
    Returns 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
    hasIdentity(Object obj)
    Preview.
    Returns true if the specified object reference is an identity object, otherwise false.
    static boolean
    isNull(Object obj)
    Returns true if the provided reference is null; false otherwise.
    static boolean
    nonNull(Object obj)
    Returns true if the provided reference is non-null; false otherwise.
    static <T> T
    requireIdentity(T obj)
    Preview.
    Checks that the specified object reference is an identity object.
    static <T> T
    requireIdentity(T obj, String message)
    Preview.
    Checks that the specified object reference is an identity object.
    static <T> T
    requireIdentity(T obj, Supplier<String> messageSupplier)
    Preview.
    Checks that the specified object reference is an identity object.
    static <T> T
    requireNonNull(T obj)
    Checks that the specified object reference is not null.
    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
    requireNonNullElse(T obj, T defaultObj)
    Returns the first argument if it is non-null and otherwise the second argument if it is non-null.
    static <T> T
    requireNonNullElseGet(T obj, Supplier<? extends T> supplier)
    Returns the first argument if it is non-null and otherwise the value from supplier.get() if it is non-null.
    static String
    toIdentityString(Object o)
    Returns a string equivalent to the string returned by Object.toString if that method and hashCode are not overridden.
    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 the second argument otherwise.

    Methods declared in class java.lang.Object

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

  • Method Details

    • 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 - 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:

    • 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 - 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:

    • hashCode

      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:

    • hash

      public static int hash(Object... values)
      Returns 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 - the values to be hashed
      Returns:
      a hash code for a sequence of input values
      See Also:

    • 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 - an object
      Returns:
      the result of calling toString for a non-null argument and "null" for a null argument
      See Also:

    • 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 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 the first argument is not null and the second argument otherwise
      See Also:

    • toIdentityString

      public static String toIdentityString(Object o)
      Returns a string equivalent to the string returned by Object.toString if that method and hashCode are not overridden.
      Implementation Requirements:
      The method returns a string equivalent to:
      o.getClass().getName() + "@" + Integer.toHexString(System.identityHashCode(o))
      Implementation Note:
      This method constructs a string for an object without calling any overridable methods of the object.
      Parameters:
      o - an object
      Returns:
      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
      Since:
      19
      See Also:

    • hasIdentity

      public static boolean hasIdentity(Object obj)
      hasIdentity is a preview API of the Java platform.
      Programs can only use hasIdentity when preview features are enabled.
      Preview features may be removed in a future release, or upgraded to permanent features of the Java platform.
      Returns true if the specified object reference is an identity object, otherwise false.
      Parameters:
      obj - an object
      Returns:
      true if the specified object reference is an identity object, otherwise false
      Throws:
      NullPointerException - if obj is null

    • requireIdentity

      public static <T> T requireIdentity(T obj)
      requireIdentity is a preview API of the Java platform.
      Programs can only use requireIdentity when preview features are enabled.
      Preview features may be removed in a future release, or upgraded to permanent features of the Java platform.
      Checks that the specified object reference is an identity object.
      Type Parameters:
      T - the type of the reference
      Parameters:
      obj - the object reference to check for identity
      Returns:
      obj if obj is an identity object
      Throws:
      NullPointerException - if obj is null
      IdentityExceptionPREVIEW - if obj is not an identity object
      Since:
      Valhalla

    • requireIdentity

      public static <T> T requireIdentity(T obj, String message)
      requireIdentity is a preview API of the Java platform.
      Programs can only use requireIdentity when preview features are enabled.
      Preview features may be removed in a future release, or upgraded to permanent features of the Java platform.
      Checks that the specified object reference is an identity object.
      Type Parameters:
      T - the type of the reference
      Parameters:
      obj - the object reference to check for identity
      message - detail message to be used in the event that an IdentityException is thrown; may be null
      Returns:
      obj if obj is an identity object
      Throws:
      NullPointerException - if obj is null
      IdentityExceptionPREVIEW - if obj is not an identity object
      Since:
      Valhalla

    • requireIdentity

      public static <T> T requireIdentity(T obj, Supplier<String> messageSupplier)
      requireIdentity is a preview API of the Java platform.
      Programs can only use requireIdentity when preview features are enabled.
      Preview features may be removed in a future release, or upgraded to permanent features of the Java platform.
      Checks that the specified object reference is an identity object.
      Type Parameters:
      T - the type of the reference
      Parameters:
      obj - the object reference to check for identity
      messageSupplier - supplier of the detail message to be used in the event that an IdentityException is thrown; may be null
      Returns:
      obj if obj is an identity object
      Throws:
      NullPointerException - if obj is null
      IdentityExceptionPREVIEW - if obj is not an identity object
      Since:
      Valhalla

    • compare

      public 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. 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.

      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:

    • 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 - if obj is null

    • requireNonNull

      public 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. 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 - if obj is null

    • isNull

      public static boolean isNull(Object obj)
      Returns true if the provided reference is null; false otherwise.
      API Note:
      This method exists to be used as a Predicate, filter(Objects::isNull)
      Parameters:
      obj - a reference to be checked against null
      Returns:
      true if the provided reference is null; false otherwise
      Since:
      1.8
      See Also:

    • nonNull

      public static boolean nonNull(Object obj)
      Returns true if the provided reference is non-null; false otherwise.
      API Note:
      This method exists to be used as a Predicate, filter(Objects::nonNull)
      Parameters:
      obj - a reference to be checked against null
      Returns:
      true if the provided reference is non-null; false otherwise
      Since:
      1.8
      See Also:

    • requireNonNullElse

      public static <T> T requireNonNullElse(T obj, T defaultObj)
      Returns the first argument if it is non-null and otherwise the second argument if it is non-null.
      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 - if both obj is null and defaultObj is null
      Since:
      9

    • requireNonNullElseGet

      public static <T> T requireNonNullElseGet(T obj, Supplier<? extends T> supplier)
      Returns the first argument if it is non-null and otherwise the value from supplier.get() if it is non-null.
      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 - 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<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.

      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 - 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 - 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 - 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 - if the sub-range is out of bounds
      Since:
      9

    • getObjectSize

      public static long getObjectSize(Object o)
      Return the size of the object in the heap.
      Parameters:
      o - an object
      Returns:
      the objects's size
      Since:
      Valhalla

    • 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 - the index
      length - the upper-bound (exclusive) of the range
      Returns:
      index if it is within bounds of the range
      Throws:
      IndexOutOfBoundsException - if the index is out of bounds
      Since:
      16

    • 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 - 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 - if the sub-range is out of bounds
      Since:
      16

    • 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 - 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 - if the sub-range is out of bounds
      Since:
      16