CollectionUtils permutations() Example in Java

By
Rakesh
-

In this post, we will see CollectionUtils permutations() example in Java. we will see how to use CollectionUtils permutations() method. The permutations() method returns all the permutations for a given list.

Syntax of permutations() method

public static <E> Collection<List<E>> permutations(final Collection<E> collection)

We need to add the below dependency in the maven to use org.apache.commons.collections4.CollectionUtils permutations() method. We can download the apache-commons maven dependency from here.

pom.xml changes

<dependency>
<groupId>org.apache.commons</groupId>
<artifactId>commons-collections4</artifactId>
<version>4.4</version>
</dependency>

CollectionUtils permutations() Example in Java

package com.javatute;

import org.apache.commons.collections4.CollectionUtils;

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

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

        List<String> firstList = new ArrayList<>();
        firstList.add("Jon");
        firstList.add("Mark");
        firstList.add("Mike");
        List<List<String>> newList = (List<List<String>>) CollectionUtils.permutations(firstList);
        System.out.println(newList);
    }
}

Output is

[[Jon, Mark, Mike], [Jon, Mike, Mark], [Mike, Jon, Mark], [Mike, Mark, Jon], [Mark, Mike, Jon], [Mark, Jon, Mike]]

How to generate all permutations of a List?

We can use CollectionUtils permutations() method.

Note – Internally permutations() method uses PermutationIterator class. In

That’s all about CollectionUtils permutations() Example in Java.

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