- Java.util Package Classes
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- Java.util Package Extras
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- Java.util Useful Resources
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- Java.util - Discussion
Java Vector retainAll() Method
Description
The Java Vector retainAll(Collection<?> c) method is used to retain only the elements in this Vector that are contained in the specified Collection. In other words, removes from this Vector all of its elements that are not contained in the specified Collection.
Declaration
Following is the declaration for java.util.Vector.retainAll() method
public boolean retainAll(Collection<?> c)
Parameters
c − This is the collection of elements to be retained in this Vector.
Return Value
The method call returns true if this Vector is changed as a result of the call.
Exception
NullPointerException − This exception is thrown if the specified collection is null.
Retaining Elements of a Vector of Integer Example
The following example shows the usage of Java Vector retainAll(collection) method. We're creating an Vector of Integers, adding some elements, print it and then use retainAll(collection) method to retain few elements. As Vector is modified it is printed to check if specified elements are removed or not.
package com.tutorialspoint; import java.util.Vector; import java.util.Arrays; public class VectorDemo { public static void main(String[] args) { // create an empty vector Vector<Integer> vector = new Vector<>(); // use add() method to add elements in the vector vector.add(20); vector.add(15); vector.add(30); vector.add(45); // let us print all the elements available in vector System.out.println("Vector = " + vector); // it will retain two common elements System.out.println("Vector modified: " + vector.retainAll(Arrays.asList(11,30,20,12))); // let us print all the elements available in vector again System.out.println("Vector = " + vector); } }
Output
Let us compile and run the above program, this will produce the following result −
Vector = [20, 15, 30, 45] Vector modified: true Vector = [20, 30]
Retaining Elements of a Vector of String Example
The following example shows the usage of Java Vector retainAll(collection) method. We're creating an Vector of Strings, adding some elements, print it and then use retainAll(collection) method to remove few elements. As Vector is modified it is printed to check if specified elements are removed or not.
package com.tutorialspoint; import java.util.Vector; import java.util.Arrays; public class VectorDemo { public static void main(String[] args) { // create an empty vector Vector<String> vector = new Vector<>(); // use add() method to add elements in the vector vector.add("A"); vector.add("B"); vector.add("C"); vector.add("D"); // let us print all the elements available in vector System.out.println("Vector = " + vector); // it will retain two common elements System.out.println("Vector modified: " + vector.retainAll(Arrays.asList("B","C","E"))); // let us print all the elements available in vector again System.out.println("Vector = " + vector); } }
Output
Let us compile and run the above program, this will produce the following result −
Vector = [A, B, C, D] Vector modified: true Vector = [B, C]
Retaining Elements of a Vector of Object Example
The following example shows the usage of Java Vector retainAll(collection) method. We're creating an Vector of Student objects, adding some elements, print it and then use retainAll(collection) method to remove few elements. As Vector is modified it is printed to check if specified elements are removed or not.
package com.tutorialspoint; import java.util.Vector; import java.util.Arrays; public class VectorDemo { public static void main(String[] args) { // create an empty vector Vector<Student> vector = new Vector<>(); // use add() method to add elements in the vector vector.add(new Student(1, "Julie")); vector.add(new Student(2, "Robert")); vector.add(new Student(3, "Adam")); vector.add(new Student(4, "Jene")); // let us print all the elements available in vector System.out.println("Vector = " + vector); // it will retain two common elements System.out.println("Vector modified: " + vector.retainAll(Arrays.asList(new Student(1, "Julie"),new Student(3, "Adam")))); // let us print all the elements available in vector again System.out.println("Vector = " + vector); } } class Student { int rollNo; String name; Student(int rollNo, String name){ this.rollNo = rollNo; this.name = name; } @Override public String toString() { return "[ " + this.rollNo + ", " + this.name + " ]"; } @Override public boolean equals(Object obj) { Student s = (Student)obj; return this.rollNo == s.rollNo && this.name.equalsIgnoreCase(s.name); } }
Output
Let us compile and run the above program, this will produce the following result −
Vector = [[ 1, Julie ], [ 2, Robert ], [ 3, Adam ], [ 4, Jene ]] Vector modified: true Vector = [[ 1, Julie ], [ 3, Adam ]]