In this Tutorial we will learn how to remove all elements from arraylist java or how to clear arraylist . We have these method to make clean or empty ararylist
1. ArrayList.clear() Method
Syntax:
public void clear() {
}This method removes all of the elements from this list. The list will be empty after this call returns.
import java.util.ArrayList;
public class RemoveAll {
public static void main(String[] args) {
ArrayList<String> arr = new ArrayList<String>();
// add element in arraylist
arr.add("c");
arr.add("c");
arr.add("php");
arr.add("html");
arr.add("java");
// print arraylist
System.out.println("arrayList is = " + arr);
/*
* Removes all of the elements from this list.
*/
arr.clear();
System.out.println("After Clear arrayList is="+arr);
}
}Output:
arrayList is = [c, c, php, html, java]
After Clear arrayList is=[]2. ArrayList().removeAll Method
Syntax :
public boolean removeAll(Collection<?> c) {
}- This method removes from this list all of its elements that are contained in the given collection.
- It take collection c as paramater , which containing elements to be removed from this list
- It returns true if this list changed as a result of the call
- It throws ClassCastException – if the class of an element of this list is incompatible with the specified collection (optional)
NullPointerException – if this list contains a null element and the specified collection does not permit null elements (optional), or if the specified collection is null
import java.util.ArrayList;
public class RemoveAll2 {
public static void main(String[] args) {
ArrayList<String> arr = new ArrayList<String>();
// add element in arraylist
arr.add("c");
arr.add("php");
arr.add("html");
arr.add("java");
// print arraylist
System.out.println("Before Removing arrayList is = " + arr);
arr.removeAll(arr);
System.out.println("After Remove all element of aarraylist is="+arr);
}
}Output:
Before Removing arrayList is = [c, php, html, java]
After Remove all element of aarraylist is=[]