How to Compare two Collections in Java?

Java Collection provides an architecture to store and manipulate the group of objects. Here we will see how to compare Elements in a Collection in Java.

Steps:

• Take both inputs with help of asList() function.
• Sort them using Collections.sort() method.
• Compare them using equals() function.
• Print output. (true means both are equal and false means both are different)

Example 1:

Java

// Java program implementing
// Comparing elements of Collections

import java.util.*;
import java.io.*;

public class ArrayCompareExample {

    // main function accepting string arguments
    public static void main(String[] args)
    {
        // create listA
        ArrayList<String> listA
            = new ArrayList<>(Arrays.asList("a", "b", "c"));

        // create listB
        ArrayList<String> listB
            = new ArrayList<>(Arrays.asList("a", "b", "d"));

        // sorting both lists
        Collections.sort(listA);
        Collections.sort(listB);

        // Compare lists using
        // equals() method
        boolean isEqual = listA.equals(listB);

        // print output on screen (true or false)
        System.out.println(isEqual);
    }
}

Output

false

Example 2:

Java

// Java program implementing
// Comparing elements of Collections

import java.util.*;
import java.io.*;

public class ArrayCompareExample {

    // main function accepting string arguments
    public static void main(String[] args)
    {
        // create listA
        ArrayList<Integer> listA
            = new ArrayList<>(Arrays.asList(3, 4, 5));

        // create listB
        ArrayList<Integer> listB
            = new ArrayList<>(Arrays.asList(4, 5, 3));

        // sorting both lists
        Collections.sort(listA);
        Collections.sort(listB);

        // Compare lists using
        // equals() method
        boolean isEqual = listA.equals(listB);

        // print output on screen (true or false)
        System.out.println(isEqual);
    }
}

Output

true