Java ArrayList set() Method

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Description

The Java ArrayList set(int index, E element) replaces the element at the specified position in this list with the specified element. The size of the arraylist remains same after this operation on the arraylist.

Declaration

Following is the declaration for java.util.ArrayList.set() method

public E set(int index, E element)

Parameters

• index − This is the index of the element to replace.

• element − This is the element to be stored at the specified position.

Return Value

This method returns the element previously at the specified position.

Exception

IndexOutOfBoundsException − If the index is out of range

Example

The following example shows the usage of java.util.Arraylist.set() method.

Updating an Element of an ArrayList of Integers Example

The following example shows the usage of Java ArrayList set(index, element) method. We're adding couple of Integers to the ArrayList object using add() method calls per element and using set(index, element) method, we're insert one of the element by index in between and printing it.

package com.tutorialspoint;

import java.util.ArrayList;

public class ArrayListDemo {
   public static void main(String[] args) {
      
      // create an empty array list 
      ArrayList<Integer> arrayList = new ArrayList<>();

      // use add() method to add elements in the arrayList
      arrayList.add(20);
      arrayList.add(30);
      arrayList.add(20);
      arrayList.add(30);
      arrayList.add(15);
      arrayList.add(22);
      arrayList.add(11);

      // insert an element at index 2
      arrayList.set(2, 50);

      // let us print the 3rd element
      System.out.println("3rd Element = " + arrayList.get(2));
   }
}

Output

Let us compile and run the above program, this will produce the following result −

3rd Element = 50

Updating an Element of an ArrayList of Strings Example

The following example shows the usage of Java ArrayList set(index, element) method. We're adding couple of Strings to the ArrayList object using add() method calls per element and using set(index, element) method, we're insert one of the element by index in between and printing it.

package com.tutorialspoint;

import java.util.ArrayList;

public class ArrayListDemo {
   public static void main(String[] args) {
      
      // create an empty array list
      ArrayList<String> arrayList = new ArrayList<>();

      // use add() method to add elements in the arrayList
      arrayList.add("Welcome");
      arrayList.add("To");
      arrayList.add("Tutorialspoint");

      // insert an element at index 2
      arrayList.set(2, "World Of");
	  
      // let us print the 3rd element
      System.out.println("3rd Element = " + arrayList.get(2));     
   }
}

Output

Let us compile and run the above program, this will produce the following result −

3rd Element = World Of

Updating an Element of an ArrayList of Objects Example

The following example shows the usage of Java ArrayList set(index, element) method. We're adding couple of Student objects to the ArrayList object using add() method calls per element and using set(index, element) method, we're insert one of the element by index in between and printing it.

package com.tutorialspoint;

import java.util.ArrayList;

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

      // create an empty arrayList
      ArrayList<Student> arrayList = new ArrayList<>();

      // use add() method to add elements in the arrayList
      arrayList.add(new Student(1, "Julie"));
      arrayList.add(new Student(2, "Robert"));
      arrayList.add(new Student(3, "Adam"));
	  
      // insert an element at index 2
      arrayList.set(2, new Student(4, "Jene"));

      // let us print the 3rd element
      System.out.println("3rd Element = " + arrayList.get(2));      
   }
}

class Student {
   int rollNo;
   String name;

   Student(int rollNo, String name){
      this.rollNo = rollNo;
      this.name = name;
   }

   @Override
   public String toString() {
      return "[ " + this.rollNo + ", " + this.name + " ]";
   }
}

Output

Let us compile and run the above program, this will produce the following result −

3rd Element = [ 4, Jene ]