Java – Arrays

Table of Contents

Java Arrays Class

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Introduction

The Java Arrays class contains a static factory that allows arrays to be viewed as lists. Following are the important points about Arrays −

This class contains various methods for manipulating arrays (such as sorting and searching).
The methods in this class throw a NullPointerException if the specified array reference is null.

Arrays Class Declaration

Following is the declaration for java.util.Arrays class −

public class Arrays
   extends Object

Arrays Class Methods

Sr.No.	Method & Description
1	static <T> List<T> asList(T… a) This method returns a fixed-size list backed by the specified array.
2	static int binarySearch(byte[] a, byte key) This method searches the specified array of bytes for the specified value using the binary search algorithm.
3	static int binarySearch(char[] a, char key) This method searches the specified array of chars for the specified value using the binary search algorithm.
4	static int binarySearch(double[] a, double key) This method searches the specified array of doubles for the specified value using the binary search algorithm.
5	static int binarySearch(float[] a, float key) This method searches the specified array of floats for the specified value using the binary search algorithm.
6	static int binarySearch(int[] a, int key) This method searches the specified array of ints for the specified value using the binary search algorithm.
7	static int binarySearch(long[] a, int fromIndex, int toIndex, long key) This method searches a range of the specified array of longs for the specified value using the binary search algorithm.
8	static int binarySearch(Object[] a, Object key) This method searches the specified array for the specified object using the binary search algorithm.
9	static int binarySearch(short[] a, short key) This method searches the specified array of shorts for the specified value using the binary search algorithm.
10	static <T> int binarySearch(T[] a, T key, Comparator<? super T> c) This method searches the specified array for the specified object using the binary search algorithm.
11	static int compare(boolean[] a, boolean[] b) This method compares two boolean arrays lexicographically.
12	static int compare(byte[] a, byte[] b) This method compares two byte arrays lexicographically.
13	static int compare(char[] a, char[] b) This method compares two char arrays lexicographically.
14	static int compare(double[] a, double[] b) This method compares two double arrays lexicographically.
15	static int compare(float[] a, float[] b) This method compares two float arrays lexicographically.
16	static int compare(int[] a, int[] b) This method compares two int arrays lexicographically.
17	static int compare(long[] a, long[] b) This method compares two long arrays lexicographically.
18	static int compare(short[] a, short[] b) This method compares two short arrays lexicographically.
19	compareUnsigned(byte[] a, byte[] b) This method compares two byte arrays lexicographically, numerically treating elements as unsigned.
20	compareUnsigned(int[] a, int[] b) This method compares two int arrays lexicographically, numerically treating elements as unsigned.
21	compareUnsigned(long[] a, long[] b) This method compares two long arrays lexicographically, numerically treating elements as unsigned.
22	compareUnsigned(short[] a, short[] b) This method compares two short arrays lexicographically, numerically treating elements as unsigned.
23	static boolean[] copyOf(boolean[] original, int newLength) This method copies the specified array, truncating or padding with false (if necessary) so the copy has the specified length.
24	static byte[] copyOf(byte[] original, int newLength) This method copies the specified array, truncating or padding with false (if necessary) so the copy has the specified length.
25	static char[] copyOf(char[] original, int newLength) This method copies the specified array, truncating or padding with false (if necessary) so the copy has the specified length.
26	static double[] copyOf(double[] original, int newLength) This method copies the specified array, truncating or padding with false (if necessary) so the copy has the specified length.
27	static float[] copyOf(float[] original, int newLength) This method copies the specified array, truncating or padding with zeros (if necessary) so the copy has the specified length.
28	static int[] copyOf(int[] original, int newLength) This method copies the specified array, truncating or padding with zeros (if necessary) so the copy has the specified length.
29	static long[] copyOf(long[] original, int newLength) This method copies the specified array, truncating or padding with zeros (if necessary) so the copy has the specified length.
30	static short[] copyOf(short[] original, int newLength) This method copies the specified array, truncating or padding with zeros (if necessary) so the copy has the specified length.
31	static <T> T[] copyOf(T[] original, int newLength) This method copies the specified array, truncating or padding with nulls (if necessary) so the copy has the specified length.
32	static <T, U> T[] copyOf(U[] original, int newLength,Class<? extends T[]> newType) This method copies the specified array, truncating or padding with nulls (if necessary) so the copy has the specified length.
33	static boolean[] copyOfRange(boolean[] original, int from, int to) This method copies the specified range of the specified array into a new array.
34	static byte[] copyOfRange(byte[] original, int from, int to) This method copies the specified range of the specified array into a new array.
35	static char[] copyOfRange(char[] original, int from, int to) This method copies the specified range of the specified array into a new array.
36	static double[] copyOfRange(double[] original, int from, int to) This method copies the specified range of the specified array into a new array.
37	static int[] copyOfRange(int[] original, int from, int to) This method copies the specified range of the specified array into a new array.
38	static long[] copyOfRange(long[] original, int from, int to) This method copies the specified range of the specified array into a new array.
39	static short[] copyOfRange(short[] original, int from, int to) This method copies the specified range of the specified array into a new array.
40	static <T> T[] copyOfRange(T[] original, int from, int to) This method copies the specified range of the specified array into a new array.
41	static <T,U> T[] copyOfRange(U[] original, int from, int to, Class<? extends T[]> newType) This method copies the specified range of the specified array into a new array.
42	static boolean deepEquals(Object[] a1, Object[] a2) This method returns true if the two specified arrays are deeply equal to one another.
43	static int deepHashCode(Object[] a) This method returns a hash code based on the “deep contents” of the specified array.
44	static String deepToString(Object[] a) This method returns a string representation of the “deep contents” of the specified array.
45	static boolean equals(boolean[] a, boolean[] a2) This method returns true if the two specified arrays of booleans are equal to one another.
46	static boolean equals(byte[] a, byte[] a2) This method returns true if the two specified arrays of bytes are equal to one another.
47	static boolean equals(char[] a, char[] a2) This method returns true if the two specified arrays of chars are equal to one another.
48	static boolean equals(double[] a, double[] a2) This method returns true if the two specified arrays of double are equal to one another.
49	static boolean equals(float[] a, float[] a2) This method returns true if the two specified arrays of floats are equal to one another.
50	static boolean equals(int[] a, int[] a2) This method returns true if the two specified arrays of ints are equal to one another.
51	static boolean equals(long[] a, long[] a2) This method returns true if the two specified arrays of longs are equal to one another.
52	static boolean equals(short[] a, short[] a2) This method returns true if the two specified arrays of shorts are equal to one another.
53	static boolean equals(Object[] a, Object[] a2) This method returns true if the two specified arrays of Objects are equal to one another.
54	static boolean equals(T[] a, T[] a2, Comparator<? super T> cmp) This method returns true if the two specified arrays of Objects are equal to one another.
55	static void fill(boolean[] a, boolean val) This method assigns the specified boolean value to each element of the specified array of booleans.
56	static void fill(byte[] a, byte val) This method assigns the specified byte value to each element of the specified array of bytes.
57	static void fill(char[] a, char val) This method assigns the specified char value to each element of the specified array of chars.
58	static void fill(double[] a, double val) This method assigns the specified double value to each element of the specified array of doubles.
59	static void fill(float[] a, float val) This method assigns the specified float value to each element of the specified array of floats.
60	static void fill(int[] a, int val) This method assigns the specified int value to each element of the specified array of ints.
61	static void fill(long[] a, long val) This method assigns the specified long value to each element of the specified array of longs.
62	static void fill(Object[] a, Object val) This method assigns the specified Object reference to each element of the specified array of Objects.
63	static void fill(short[] a, short val) This method assigns the specified short value to each element of the specified array of shorts.
64	static int hashCode(boolean[] a) This method returns a hash code based on the contents of the specified array.
65	static int mismatch(boolean[] a, boolean[] b) This method finds and returns the index of the first mismatch between two boolean arrays, otherwise return -1 if no mismatch is found.
66	static int mismatch(byte[] a, byte[] b) This method finds and returns the index of the first mismatch between two byte arrays, otherwise return -1 if no mismatch is found.
67	static int mismatch(char[] a, char[] b) This method finds and returns the index of the first mismatch between two char arrays, otherwise return -1 if no mismatch is found.
68	static int mismatch(double[] a, double[] b) This method finds and returns the index of the first mismatch between two double arrays, otherwise return -1 if no mismatch is found.
69	static int mismatch(int[] a, int[] b) This method finds and returns the index of the first mismatch between two int arrays, otherwise return -1 if no mismatch is found.
70	static int mismatch(long[] a, long[] b) This method finds and returns the index of the first mismatch between two long arrays, otherwise return -1 if no mismatch is found.
71	static int mismatch(short[] a, short[] b) This method finds and returns the index of the first mismatch between two short arrays, otherwise return -1 if no mismatch is found.
72	static int mismatch(Object[] a, Object[] b) This method finds and returns the index of the first mismatch between two object arrays, otherwise return -1 if no mismatch is found.
73	static int mismatch(T[] a, T[] b, Comparator<? super T> cmp) This method finds and returns the index of the first mismatch between two object arrays, otherwise return -1 if no mismatch is found.
74	static void parallelPrefix(double[] array, DoubleBinaryOperator op) This method cumulates, in parallel, each element of the given array in place, using the supplied function.
75	static void parallelPrefix(int[] array, IntBinaryOperator op) This method cumulates, in parallel, each element of the given array in place, using the supplied function.
76	static void parallelPrefix(long[] array, LongBinaryOperator op) This method cumulates, in parallel, each element of the given array in place, using the supplied function.
77	static <T> void parallelPrefix(T[] array, BinaryOperator<T> op) This method cumulates, in parallel, each element of the given array in place, using the supplied function.
78	static void parallelSetAll(double[] array, IntToDoubleFunction generator) This method sets all elements of the specified array, in parallel, using the provided generator function to compute each element.
79	static void parallelSetAll(int[] array, IntUnaryOperator generator) This method sets all elements of the specified array, in parallel, using the provided generator function to compute each element.
80	static void parallelSetAll(long[] array, IntToLongFunction generator) This method sets all elements of the specified array, in parallel, using the provided generator function to compute each element.
81	static <T> void parallelSetAll(T[] array, IntFunction<? extends T> generator) This method sets all elements of the specified array, in parallel, using the provided generator function to compute each element.
82	static void parallelSort(byte[] a) This method sorts the specified array of bytes into ascending numerical order.
83	static void parallelSort(char[] a) This method sorts the specified array of chars into ascending numerical order.
84	static void parallelSort(double[] a) This method sorts the specified array of doubles into ascending numerical order.
85	static void parallelSort(float[] a) This method sorts the specified array of floats into ascending numerical order.
86	static void parallelSort(int[] a) This method sorts the specified array of ints into ascending numerical order.
87	static void parallelSort(long[] a) This method sorts the specified array of longs into ascending numerical order.
88	static void parallelSort(short[] a) This method sorts the specified array of shorts into ascending numerical order.
89	static <T extends Comparable<? super T>> void parallelSort(T[] a) This method sorts the specified array of objects into ascending order, according to the natural ordering of its elements.
90	static <T>> void parallelSort(T[] a, Comparator<? super T> cmp) This method sorts the specified array of objects into ascending order, according to the ordering provided by the Comparator instance.
91	static void setAll(double[] array, IntToDoubleFunction generator) This method sets all elements of the specified array, using the provided generator function to compute each element.
92	static void setAll(int[] array, IntUnaryOperator generator) This method sets all elements of the specified array, using the provided generator function to compute each element.
93	static void setAll(long[] array, IntToLongFunction generator) This method sets all elements of the specified array, using the provided generator function to compute each element.
94	static <T> void setAll(T[] array, IntFunction<? extends T> generator) This method sets all elements of the specified array, using the provided generator function to compute each element.
95	static Spliterator.OfDouble spliterator(double[] array) This method returns a Spliterator.OfDouble covering all of the specified array.
96	static Spliterator.OfInt spliterator(int[] array) This method returns a Spliterator.OfInt covering all of the specified array.
97	static Spliterator.OfLong spliterator(long[] array) This method returns a Spliterator.OfLong covering all of the specified array.
98	static <T> Spliterator<T> spliterator(T[] array) This method returns a Spliterator covering all of the specified array.
99	static DoubleStream stream(double[] array) This method returns a sequential DoubleStream with the specified array as its source.
100	static IntStream stream(int[] array) This method returns a sequential IntStream with the specified array as its source.
101	static LongStream stream(long[] array) This method returns a sequential LongStream with the specified array as its source.
102	static <T> Stream<T> stream(T[] array) This method returns a sequential Stream with the specified array as its source.
103	static void sort(byte[] a) This method sorts the specified array of bytes into ascending numerical order.
104	static void sort(char[] a) This method sorts the specified array of chars into ascending numerical order.
105	static void sort(double[] a) This method sorts the specified array of doubles into ascending numerical order.
106	static void sort(float[] a) This method sorts the specified array of floats into ascending numerical order.
107	static void sort(int[] a) This method sorts the specified array of ints into ascending numerical order.
108	static void sort(long[] a) This method sorts the specified array of longs into ascending numerical order.
109	static void sort(Object[] a) This method sorts the specified array of objects into ascending order, according to the natural ordering of its elements.
110	static void sort(short[] a) This method sorts the specified array of shorts into ascending numerical order.
111	static String toString(boolean[] a) This method returns a string representation of the contents of the specified array of boolean.

Methods Inherited

This class inherits methods from the following classes −

java.util.Object

Arrays Class Example

This Java example demonstrates the binarySearch() method of Arrays class.

// Importing the Arrays class
import java.util.Arrays;

// Public Main Class
public class Main {
  public static void main(String[] args) {
    // Declaring an array
    int arr[] = {8, 5, 3, 10, 2, 1, 15, 20};

    // Sorting the array
    Arrays.sort(arr);

    // Taking an element to search
    int ele = 15;

    // Using binarySearch() method to search "ele"
    System.out.println(
      ele + " presents at the index = " +
      Arrays.binarySearch(arr, ele));
  }
}

Let us compile and run the above program, this will produce the following result −

15 presents at the index = 6

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