Java – Array Operations

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Copying an array:

1. Using arraycopy() method:

The arraycopy() method belongs to the System class. It is used to copy the contents of one array to the other.

Type

public static void

Description
Method


arraycopy(Object src, int srcPos, Object dest, int destPos, int length)

Copies an array from the source array, beginning at the specified position, to the specified position of the destination array.

length – the number of array elements to be copied.

Example:

COMPILE & RUN

Output:

[6, 7, 8, 9, 10]

2. Using copyOf() and copyOfRange() method:

The Arrays class has two commonly used methods for copying the content of array i.e. copyOf() and copyOfRange() method. The Generic type T[] can be replaced with any other primitive type.


Type

public static T[]

public static T[]

Description
Method

copyOf(T[] original, int newLength)

copyOfRange(T[] original, int from, int to)

Returns a new array which is a copy of the array specified and padded with 0s to obtain the specified length. newLength is the number of array elements to be copied.

Returns a new array containing the specified range from the original array, truncated or padded with nulls to obtain the required length.

Example:

COMPILE & RUN

Output:

[5, 6, 7, 8, 9, 10, 0, 0] [5, 6, 7, 8, 9]

Manipulation of Array:

The java.util.Arrays class provides several methods for manipulating arrays (copying, sorting, searching etc.)

Commonly used methods of the class ‘Arrays’:

Methods Description
static int binarySearch(int[] a, int key) Searches the specified array for the given value using the binary search algorithm and returns the value.
static int binarySearch(int[] a, int fromIndex, int toIndex, int key) Searches between the range specified in the specified array for the given value using the binary search algorithm and returns the value.
static boolean equals(int[] a, int[] a2) Returns true if the given arrays are equal.
static void fill(int[] a, int val) Assigns the value ‘val’ to each element in the array specified.
static int hashCode(int[] a) Returns a hashcode of the specified array.
static void parallelSort(int[] a) Sorts the specified array into ascending order. This works well with array with huge number of elements.
static void sort(int[] a) Sorts the specified array into ascending order. This is a serial sorting method and works well with small to large arrays.

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