Stack trimToSize() method in Java with Example

The trimToSize() method of Stack in Java trims the capacity of an Stack instance to be the list’s current capacity. This method is used to trim an Stack instance to the number of elements it contains.

Syntax:

public void trimToSize()

Parameter: It does not accepts any parameter.

Return Value: It does not returns any value. It trims the capacity of this Stack instance to the number of the element it contains.

Below program illustrate the trimToSize() method:

// Java code to demonstrate the working of
// trimToSize() method in Stack

// for Stack functions
import java.util.Stack;

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

        // Creating object of Stack<Integer>
        Stack<Integer>
            stack = new Stack<Integer>();

        // adding element to stack
        stack.add(10);
        stack.add(20);
        stack.add(30);
        stack.add(40);

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

        // Print the current capacity of Stack
        System.out.println("Current capacity of Stack: "
                           + stack.capacity());

        // Change the capacity to 15
        stack.ensureCapacity(15);

        // Print the current capacity of Stack
        System.out.println("New capacity of Stack: "
                           + stack.capacity());

        // trims the capacity to the number of elements
        stack.trimToSize();

        // Print the current capacity of Stack
        System.out.println("Current capacity of Stack"
                           + " after use of trimToSize() method: "
                           + stack.capacity());
    }
}

Output:

Stack: [10, 20, 30, 40]
Current capacity of Stack: 10
New capacity of Stack: 20
Current capacity of Stack after use of trimToSize() method: 4

Example 2:

// Java program to demonstrate
// Stack toString() method

import java.util.*;

public class collection {
    public static void main(String args[])
    {
        // Creating an Empty Stack
        Stack<String> stack
            = new Stack<String>();

        // Use add() method
        // to add elements to the Collection
        stack.add("Welcome");
        stack.add("To");
        stack.add("Geeks");
        stack.add("For");
        stack.add("Geeks");

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

        // Print the current capacity of Stack
        System.out.println("Current capacity of Stack: "
                           + stack.capacity());

        // Change the capacity to 20
        stack.ensureCapacity(20);

        // Print the current capacity of Stack
        System.out.println("New capacity of Stack: "
                           + stack.capacity());

        // trims the capacity to the number of elements
        stack.trimToSize();

        // Print the current capacity of Stack
        System.out.println("Current capacity of Stack"
                           + " after use of trimToSize() method: "
                           + stack.capacity());
    }
}

Output:

Stack: [Welcome, To, Geeks, For, Geeks]
Current capacity of Stack: 10
New capacity of Stack: 20
Current capacity of Stack after use of trimToSize() method: 5