Java retainAll example 2018-03-20 06:32
retainAll method is used to remove the elements which not in both collections. The example code is here.
public class RetainAllClient {
public static void main(String[] args) {
List<String> a = new ArrayList<>();
a.add("1");
a.add("2");
a.add("3");
a.add("4");
List<String> b = new ArrayList<>();
b.add("1");
b.add("2");
b.add("4");
b.add("5");
System.out.println(a.retainAll(b));
System.out.println(a);
System.out.println(b);
}
}
a.retainAll(b) means remove the elements which are not in both a and b list. The element "5" is only in b list, remove it from a list after calling the method. The output is like following.
true
[1, 2, 4]
[1, 2, 4, 5]
The return of retainAll means the original collection is changed or not.
EOF