The java.util.ArrayList.clear() method removes all of the elements from this list. The list will be empty after this call returns.

Java ArrayList clear() Method Example

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

import java.util.ArrayList;

public class ArrayListDemo {
   public static void main(String[] args) {
     
      // create an empty array list with an initial capacity
      ArrayList<Integer> arrlist = new ArrayList<Integer>(5);

      // use add() method to add elements in the list
      arrlist.add(20);
      arrlist.add(30);
      arrlist.add(10);
      arrlist.add(50);

      // let us print all the elements available in list
      for (Integer number : arrlist) {
         System.out.println("Number = " + number);
      }      

      // finding size of this list
      int retval = arrlist.size();
      System.out.println("List consists of "+ retval +" elements");
         
      System.out.println("Performing clear operation !!");
      arrlist.clear();
      retval = arrlist.size();
      System.out.println("Now, list consists of "+ retval +" elements");
   }
}   

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

Number = 20
Number = 30
Number = 10
Number = 50
List consists of 4 elements
Performing clear operation !!
Now, list consists of 0 elements

Reference

https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/util/ArrayList.html

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