How to shuffle list elements in Java

By Atul Rai | Last Updated: July 14, 2020 Previous       Next

On this page, we are going to shuffle or randomize elements of List in Java. In this example, we randomize the ArrayList elements.

Using Collections.shuffle we can shuffle or randomize ArrayList elements.

public static void shuffle(List<?> list)

Throws: UnsupportedOperationException – if the specified list or its list-iterator does not support the set operation.

package org.websparrow;

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;

public class SuffleListElements {
	public static void main(String[] args) {

		List<String> myList = new ArrayList<>();
		try {

			myList.add("Java");
			myList.add("Struts");
			myList.add("jQuery");
			myList.add("Spring");
			myList.add("Oracle");
			myList.add("MySQL");

			System.out.println("Before suffle the list\n" + myList + "\n");

			Collections.shuffle(myList);
			System.out.println("After suffle the list\n" + myList + "\n");

			Collections.shuffle(myList);
			System.out.println("Again after suffle the list\n" + myList);

		} catch (UnsupportedOperationException e) {
			e.printStackTrace();
		}
	}
}

Output:

Before suffle the list
[Java, Struts, jQuery, Spring, Oracle, MySQL]

After suffle the list
[MySQL, jQuery, Spring, Oracle, Java, Struts]

Again after suffle the list
[Spring, jQuery, Oracle, Java, MySQL, Struts]