Stack retainAll() method in Java with Example
The retainAll() method of java.util.Stack class is used to retain from this stack 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 stack.
Returns Value: This method returns true if this stack changed as a result of the call.
Exception: This method throws NullPointerException if this stack 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:
import java.util.*;
public class GFG1 {
public static void main(String[] argv) throws Exception
{
try {
Stack<Integer>
stack1 = new Stack<Integer>();
stack1.add( 1 );
stack1.add( 2 );
stack1.add( 3 );
stack1.add( 4 );
stack1.add( 5 );
System.out.println( "Stack before "
+ "retainAll() operation : "
+ stack1);
Stack<Integer>
stack2 = new Stack<Integer>();
stack2.add( 1 );
stack2.add( 2 );
stack2.add( 3 );
System.out.println( "Collection Elements"
+ " to be retained : "
+ stack2);
stack1.retainAll(stack2);
System.out.println( "Stack after "
+ "retainAll() operation : "
+ stack1);
}
catch (NullPointerException e) {
System.out.println( "Exception thrown : " + e);
}
}
}
|
Output:
Stack before retainAll() operation : [1, 2, 3, 4, 5]
Collection Elements to be retained : [1, 2, 3]
Stack after retainAll() operation : [1, 2, 3]
Example 2: For NullPointerException
import java.util.*;
public class GFG1 {
public static void main(String[] argv) throws Exception
{
try {
Stack<Integer>
stack1 = new Stack<Integer>();
stack1.add( 1 );
stack1.add( 2 );
stack1.add( 3 );
stack1.add( 4 );
stack1.add( 5 );
System.out.println( "Stack before "
+ "retainAll() operation : "
+ stack1);
Stack<Integer>
stack2 = null ;
System.out.println( "Collection Elements"
+ " to be retained : "
+ stack2);
System.out.println( "\nTrying to pass "
+ "null as a specified element\n" );
stack1.retainAll(stack2);
System.out.println( "Stack after "
+ "retainAll() operation : "
+ stack1);
}
catch (NullPointerException e) {
System.out.println( "Exception thrown : " + e);
}
}
}
|
Output:
Stack 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
Last Updated :
24 Dec, 2018
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