What is the ArrayList.removeAll() method in Java?
The ArrayList.removeAll() method in Java is used to remove all the elements in a list that a collection contains.
Syntax
The ArrayList.removeAll() method can be declared as shown in the code snippet below:
public boolean removeAll(Collection c)
Parameters
c: The collection that contains the elements that will be removed from the list.
Return value
The ArrayList.removeAll() method returns true if the elements contained by c are successfully removed from the list.
- If the class of elements of the list are incompatible with the class of elements of the collection, the
ArrayList.removeAll()method throws theClassCastException.
- If the list contains
nullelements and the collection does not allownullelements, theArrayList.removeAll()method throws theNullPointerException.
- If the collection is
null, theArrayList.removeAll()method throws theNullPointerException.
Code
Consider the code snippet below, which demonstrates the use of the ArrayList.removeAll() method.
import java.util.ArrayList;class main {public static void main(String[] args){ArrayList<Integer> list1 = new ArrayList<Integer>();list1.add(1);list1.add(2);list1.add(3);list1.add(4);list1.add(5);System.out.println("list1: " + list1);ArrayList<Integer> list2 = new ArrayList<Integer>();list2.add(2);list2.add(4);list2.add(6);System.out.println("list2: " + list2);System.out.println("list1.removeAll(list1)");list1.removeAll(list2);System.out.println("list1: " + list1);}}
Explanation
Two lists, list1 and list2, are declared in line 6 and line 15 respectively. The ArrayList.removeAll() is used in line 23 to remove all the elements contained by list2 from list1.
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