Module java.base
Package java.util

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 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 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)
    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 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 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.

    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:
      Object.equals(Object)
    • 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:
      Arrays.deepEquals(Object[], Object[]), equals(Object, Object)
    • 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:
      Object.hashCode()
    • 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 - the values to be hashed
      Returns:
      a hash value of the sequence of input values
      See Also:
      Arrays.hashCode(Object[]), List.hashCode()
    • 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:
      Object.toString(), String.valueOf(Object)
    • 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 - 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)
    • 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:
      Comparable, Comparator
    • 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 otherwise returns false.
      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 otherwise false
      Since:
      1.8
      See Also:
      Predicate
    • 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 - a reference to be checked against null
      Returns:
      true if the provided reference is non-null otherwise false
      Since:
      1.8
      See Also:
      Predicate
    • 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 - 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 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 - 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