Java Collections shuffle() Method

The shuffle() is a Java Collections class method which works by randomly permuting the specified list elements. There is two different types of Java shuffle() method which can be differentiated depending on its parameter. These are:

Java Collections shuffle(list) Method
Java Collections shuffle(list, random) Method

Java Collections shuffle(list) Method

The shuffle(list) method is used to work by randomly reorders the specified list elements using a default randomness.

Java Collections shuffle(list, random) Method

The shuffle(list, random) method is used to work by randomly reorders the list elements using the specified randomness.

Syntax

Following is the declaration of shuffle() method:

public static void shuffle(List<?> list)
public static void shuffle(List<?> list, Random random)

Parameter

Parameter	Description	Required/Optional
list	It is the list which will be shuffled.	Required
random	It is the source of randomness which is used to shuffle the list.	Required

Returns

The shuffle() method does not return anything.

Exceptions

UnsupportedOperationException- This method thrown exception if the specified list or its list-iterator does not support the set operation.

Compatibility Version

Java 1.5 and above

Example 1

import java.util.*;
public class CollectionsShuffleExample1 {
	public static void main(String[] args) {
		List<String> list = Arrays.asList("A", "B", "C", "D");
            System.out.println("List before Shuffle : "+list);
            Collections.shuffle(list);
            System.out.println("List after shuffle : "+list);
	      }
}

Test it Now

Output:

List before Shuffle : [A, B, C, D]
List after shuffle : [A, C, D, B]

Example 2

import java.util.*;
public class CollectionsShuffleExample2 {
	public static void main(String[] args) {
		//Create linked list object
	      LinkedList<Integer> list = new LinkedList<Integer>();
	      //Add values in the list
	      list.add(10);
	      list.add(-20);
	      list.add(50);
	      list.add(90);
	      list.add(-15);
            System.out.println("List before Shuffle : "+list);
            Collections.shuffle(list);
            System.out.println("List after shuffle : "+list);
	      }
}

Test it Now

Output:

List before Shuffle : [10, -20, 50, 90, -15]
List after shuffle : [10, 50, 90, -15, -20]

Example 3

import java.util.*;
public class CollectionsShuffleExample3 {
	public static void main(String[] args) {
		//Create linked list object
	      LinkedList<Integer> list = new LinkedList<Integer>();
	      //Add values in the list
	      list.add(45);
	      list.add(20);
	      list.add(55);
	      list.add(90);
	      list.add(15);
	      System.out.println("List before Shuffle = "+list);
	      //We use Random() to shuffle given list.
	      Collections.shuffle(list, new Random());
	      System.out.println("Shuffled List with Random() = "+list);	 
	      //We use Random(3) to shuffle given list.
	      Collections.shuffle(list, new Random(3));
	      System.out.println("Shuffled List with Random(3) = "+list);	       
	      }
}

Test it Now

Output:

List before Shuffle = [45, 20, 55, 90, 15]
Shuffled List with Random() = [45, 55, 15, 90, 20]
Shuffled List with Random(3) = [90, 55, 45, 15, 20]

Example 4

import java.util.*;
public class CollectionsShuffleExample4 {
	public static void main(String[] args) {		
		List<String> list = Arrays.asList("one", "two", "three", "four");
            System.out.println(list);
            Collections.shuffle(list, new Random(2));
            System.out.println(list);       
	      }
}

Test it Now

Output:

[one, two, three, four]
[four, two, one, three]

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Java Collections shuffle() Method

Java Collections shuffle(list) Method

Java Collections shuffle(list, random) Method

Syntax

Parameter

Returns

Exceptions

Compatibility Version

Example 1