Collections fill() method in Java with Examples

The fill() method of java.util.Collections class is used to replace all of the elements of the specified list with the specified element.

This method runs in linear time.

Syntax:

public static  void fill(List list, T obj)

Parameters: This method takes following argument as parameter

• list – the list to be filled with the specified element.
• obj – The element with which to fill the specified list.

Below are the examples to illustrate the fill() method

Example 1:

// Java program to demonstrate
// fill() method
// for String value

import java.util.*;

public class GFG1 {
    public static void main(String[] argv) throws Exception
    {
        // creating object of List<Integer>
        List<String> arrlist = new ArrayList<String>();

        // Adding element to srclst
        arrlist.add("A");
        arrlist.add("B");
        arrlist.add("C");

        // print the elements
        System.out.println("List elements before fill: "
                           + arrlist);

        // fill the list
        Collections.fill(arrlist, "TAJMAHAL");

        // print the elements
        System.out.println("\nList elements after fill: "
                           + arrlist);
    }
}

Output:

List elements before fill: [A, B, C]

List elements after fill: [TAJMAHAL, TAJMAHAL, TAJMAHAL]

Example 2:

// Java program to demonstrate
// fill() method
// for Integer value

import java.util.*;

public class GFG1 {
    public static void main(String[] argv) throws Exception
    {

        // creating object of List<Integer>
        List<Integer> arrlist = new ArrayList<Integer>();

        // Adding element to srclst
        arrlist.add(20);
        arrlist.add(30);
        arrlist.add(40);

        // print the elements
        System.out.println("List elements before fill: "
                           + arrlist);

        // fill the list
        Collections.fill(arrlist, 500);

        // print the elements
        System.out.println("\nList elements after fill: "
                           + arrlist);
    }
}

Output:

List elements before fill: [20, 30, 40]

List elements after fill: [500, 500, 500]