The retainAll() method of java.util.AbstractSequentialList class is used to retain from this list all of its elements that are contained in the specified collection. Syntax:
public boolean retainAll(Collection c)
Parameters: This method takes collection c as a parameter containing elements to be retained from this list. Returns Value: This method returns true if this list changed as a result of the call. Exception: This method throws 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. Below are the examples to illustrate the retainAll() method. Example 1:
// Java program to demonstrate // retainAll() method for Integer value import java.util.*;
public class GFG1 {
public static void main(String[] argv) throws Exception
{
try {
// Creating object of AbstractSequentialList<Integer>
AbstractSequentialList<Integer>
arrlist1 = new LinkedList<Integer>();
// Populating arrlist1
arrlist1.add( 1 );
arrlist1.add( 2 );
arrlist1.add( 3 );
arrlist1.add( 4 );
arrlist1.add( 5 );
// print arrlist1
System.out.println("AbstractSequentialList before "
+ "retainAll() operation : "
+ arrlist1);
// Creating another object of AbstractSequentialList<Integer>
AbstractSequentialList<Integer>
arrlist2 = new LinkedList<Integer>();
arrlist2.add( 1 );
arrlist2.add( 2 );
arrlist2.add( 3 );
// print arrlist2
System.out.println("Collection Elements"
+ " to be retained : "
+ arrlist2);
// Removing elements from arrlist
// specified in arrlist2
// using retainAll() method
arrlist1.retainAll(arrlist2);
// print arrlist1
System.out.println("AbstractSequentialList after "
+ "retainAll() operation : "
+ arrlist1);
}
catch (NullPointerException e) {
System.out.println("Exception thrown : " + e);
}
}
} |
AbstractSequentialList before retainAll() operation : [1, 2, 3, 4, 5] Collection Elements to be retained : [1, 2, 3] AbstractSequentialList after retainAll() operation : [1, 2, 3]
Example 2: For NullPointerException
// Java program to demonstrate // retainAll() method for Integer value import java.util.*;
public class GFG1 {
public static void main(String[] argv) throws Exception
{
try {
// Creating object of AbstractSequentialList<Integer>
AbstractSequentialList<Integer>
arrlist1 = new LinkedList<Integer>();
// Populating arrlist1
arrlist1.add( 1 );
arrlist1.add( 2 );
arrlist1.add( 3 );
arrlist1.add( 4 );
arrlist1.add( 5 );
// print arrlist1
System.out.println("AbstractSequentialList before "
+ "retainAll() operation : "
+ arrlist1);
// Creating another object of AbstractSequentialList<Integer>
AbstractSequentialList<Integer>
arrlist2 = null ;
// print arrlist2
System.out.println("Collection Elements"
+ " to be retained : "
+ arrlist2);
System.out.println("\nTrying to pass "
+ " null as a specified element\n");
// Removing elements from arrlist
// specified in arrlist2
// using retainAll() method
arrlist1.retainAll(arrlist2);
// print arrlist1
System.out.println("AbstractSequentialList after "
+ "retainAll() operation : "
+ arrlist1);
}
catch (NullPointerException e) {
System.out.println("Exception thrown : " + e);
}
}
} |
AbstractSequentialList before retainAll() operation : [1, 2, 3, 4, 5] Collection Elements to be retained : null Trying to pass null as a specified element Exception thrown : java.lang.NullPointerException