Stack indexOf() method in Java with Example

The Java.util.Stack.indexOf(Object element) method is used to check and find the occurrence of a particular element in the Stack. If the element is present then the index of the first occurrence of the element is returned otherwise -1 is returned if the Stack does not contain the element.

Syntax:

Stack.indexOf(Object element)

Parameters: This method accepts a mandatory parameter element of the type of Stack. It specifies the element whose occurrence is needed to be checked in the Stack.

Return Value: This method returns the index or position of the first occurrence of the element in the Stack. Else it returns -1 if the element is not present in the Stack. The returned value is of integer type.

Below programs illustrate the Java.util.Stack.indexOf() method:

Program 1:

// Java code to illustrate indexOf()
import java.util.*;

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

        // Creating an empty Stack
        Stack<String> stack = new Stack<String>();

        // Use add() method to add elements in the Stack
        stack.add("Geeks");
        stack.add("for");
        stack.add("Geeks");
        stack.add("10");
        stack.add("20");

        // Displaying the Stack
        System.out.println("Stack: " + stack);

        // The first position of an element
        // is returned
        System.out.println("The first occurrence"
                           + " of Geeks is at index:"
                           + stack.indexOf("Geeks"));
        System.out.println("The first occurrence"
                           + " of 10 is at index: "
                           + stack.indexOf("10"));
    }
}

Output:

Stack: [Geeks, for, Geeks, 10, 20]
The first occurrence of Geeks is at index:0
The first occurrence of 10 is at index: 3

Program 2:

// Java code to illustrate indexOf()
import java.util.*;

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

        // Creating an empty Stack
        Stack<Integer> stack = new Stack<Integer>();

        // Use add() method to add elements in the Stack
        stack.add(1);
        stack.add(2);
        stack.add(3);
        stack.add(10);
        stack.add(20);

        // Displaying the Stack
        System.out.println("Stack: " + stack);

        // The first position of an element
        // is returned
        System.out.println("The first occurrence"
                           + " of Geeks is at index:"
                           + stack.indexOf(2));
        System.out.println("The first occurrence"
                           + " of 10 is at index: "
                           + stack.indexOf(20));
    }
}

Output:

Stack: [1, 2, 3, 10, 20]
The first occurrence of Geeks is at index:1
The first occurrence of 10 is at index: 4