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.
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.
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
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
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