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# Java Program To Jumble an Array

• Last Updated : 24 Nov, 2020

Given an array of size N, and the task is to shuffle the elements of the array or any other permutation. Using Java think of stuffing the array by generating random sequences of the elements present in the array is possible. This Algorithm is called Fisher-Yates Shuffle Algorithm.

Fisher–Yates shuffle Algorithm Works in O(n) time complexity. The assumption is that a give a function rand() generates a random number in O(1) time. Start from the last element, swap it with a randomly selected element from the whole array. Now consider the array from 0 to n-2 (size reduced by 1), and repeat till we hit the first element.

Example:

```Input : arr[] = {1, 2, 3, 4}
Output: arr[] = {3, 2, 4, 1}

Input : arr[] = {5, 2, 3, 4}
Output: arr[] = {2, 4, 3, 5}
```

Algorithm:

```  for i from n - 1 downto 1 do
j = random integer with 0 <= j <= i
exchange a[j] and a[i]
```

Below is the implementation of the above approach:

## Java

 `// Program to jumble an array  using Java``import` `java.util.Random;``import` `java.io.*;`` ` `public` `class` `GFG {``    ``public` `static` `void` `shuffleanarray(``int``[] a)``    ``{``        ``int` `n = a.length;``        ``Random random = ``new` `Random();``        ``// generating random number from list``        ``random.nextInt();``       ` `        ``for` `(``int` `i = ``0``; i < n; i++) {``           ` `            ``// using random generated number``            ``int` `change = i + random.nextInt(n - i);``           ` `            ``// swapping elements to shuffle``            ``int` `holder = a[i];``            ``a[i] = a[change];``            ``a[change] = holder;``        ``}``    ``}``    ``public` `static` `void` `main(String[] args)``    ``{``        ``int``[] a = ``new` `int``[] { ``0``, ``1``, ``2``, ``3``, ``4``, ``5``, ``6` `};``        ``shuffleanarray(a);``        ``System.out.print(``"arr[] = {"``);``        ``for` `(``int` `i : a) {``            ``System.out.print(i + ``" "``);``        ``}``        ``System.out.print(``"}"``);``    ``}``}`
Output
```arr[] = {4 0 6 1 5 3 2 }
```

Time Complexity: O(N), where N is the size of an array.

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