Java ArrayList clear() usage and example

Java ArrayList Methods

The Java ArrayList clear() method removes all elements from the arraylist.

The syntax of the clear() method is:

arraylist.clear()

clear() parameters

The clear() method does not take any parameters.

clear() return value

The clear() method does not return any value. It clears the arraylist.

Example1: Remove all elements from a string type ArrayList

import java.util.ArrayList;
class Main {
　　　　public static void main(String[] args){
　　　　　　　　//Create arraylist
　　　　　　　　ArrayList<String> languages = new ArrayList<>();
　　　　　　　　languages.add("Java");
　　　　　　　　languages.add("JavaScript");
　　　　　　　　languages.add("Python");
　　　　　　　　System.out.println("Programming languages: ");　+　languages);
　　　　　　　　//Delete All Elements
　　　　　　　　languages.clear();
　　　　　　　　System.out.println("ArrayList after clear(): ");　+　languages);
　　　　}
}

Output Result

Programming languages: [Java, JavaScript, Python]
ArrayList after clear(): []

In the above example, we created an ArrayList named languages. The arraylist stores the names of programming languages.

Here, we have used the clear() method to remove all elements from languages.

ArrayList clear() vs removeAll()

ArrayList also provides the removeAll() method, which removes all elements from the arraylist. For example,

import java.util.ArrayList;
class Main {
　　　　public static void main(String[] args){
　　　　　　　　//　Create arraylist
　　　　　　　　ArrayList<Integer> oddNumbers = new ArrayList<>();
　　　　　　　　//　Add elements to the arraylist
　　　　　　　　oddNumbers.add(1);}}
　　　　　　　　oddNumbers.add(3);}}
　　　　　　　　oddNumbers.add(5);}}
　　　　　　　　System.out.println("Odd ArrayList:　"　+　oddNumbers);
　　　　　　　　//　Delete All Elements
　　　　　　　　oddNumbers.removeAll(oddNumbers);
　　　　　　　　System.out.println("ArrayList after removeAll():　"　+　oddNumbers);
　　　　}
}

Output Result

Odd ArrayList:　[1,　3,　5]
ArrayList after removeAll():　[]

In the above example, we created an ArrayList named oddNumbers. Here, we can see that the removeAll() method is used to delete all elements from the arraylist.

The removeAll() and clear() methods perform the same task. However, the usage rate of clear() is higher than that of removeAll(). This is because clear() is faster and more efficient than removeAll().

Java ArrayList Methods