Removing Elements from an ArrayList in Java

Using the ArrayList class in Java with the removeAll() method, we can remove the elements from one array based on the elements contained in another.

Removing Elements from an ArrayList

Two ArrayList objects, objArray and objArray2, are created and filled with sample elements. The removeAll() method is then used to remove all elements from objArray that are present in objArray2.

The removeAll(Collection<?> c) method in ArrayList removes all elements shared between the ArrayList and the specified collection. This method alters the ArrayList.

Syntax

The following is the syntax for java.util.ArrayList.remove() method

public boolean removeAll(Collection<?> c)

Java Program to Remove Elements from an ArrayList

The following example uses the removeAll() method to remove one array from another

import java.util.ArrayList;

public class Main {
   public static void main(String[] args)  {
      ArrayList objArray = new ArrayList();
      ArrayList objArray2 = new ArrayList();
      objArray2.add(0,"common1");
      objArray2.add(1,"common2");
      objArray2.add(2,"notcommon");
      objArray2.add(3,"notcommon1");
      objArray.add(0,"common1");
      objArray.add(1,"common2");
      objArray.add(2,"notcommon2");
      System.out.println("Array elements of array1" +objArray);
      System.out.println("Array elements of array2" +objArray2);
      objArray.removeAll(objArray2);
      System.out.println("Array1 after removing array2 from array1"+objArray);
   }
}

Output

Array elements of array1[common1, common2, notcommon2]
Array elements of array2[common1, common2, notcommon, notcommon1]
Array1 after removing array2 from array1[notcommon2]

Code Explanation

This example demonstrates how to remove elements from one list (objArray) that also occur in another list (objArray2). It creates two ArrayList objects and adds a few elements to each. The removeAll() method removes from objArray all elements that are found in objArray2. Finally, the modified objArray is printed to the console, containing only the elements that are not present in both lists.