indexOf method in List Interface in Java

/*
indexOf method is defined as  - int indexOf(Object obj) in List Interface
*/

import java.util.*;

public class indexOf {

    public static void main(String[] args) {

       

        ArrayList a1 = new ArrayList();

        a1.add(0,"a");

        a1.add(1,"b");

        a1.add(2,"c");

        a1.add(3,"d");

       

        System.out.println("The size of a1 is " + a1.size());

        System.out.println("The Value of a1 is " + a1.indexOf("c"));

    }

}

Answer

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The size of a1 is 4

The Value of a1 is 2