Vector removeIf() method in Java

The removeIf() method of Vector removes all of those elements from Vector which satisfies the condition passed as a parameter to this method. This method returns true if some element are removed from the Vector.

Java 8 has an important in-built functional interface which is Predicate. Predicate, or a condition checking function, which checks the given input for a given condition and returns a boolean result for the same indicating whether the condition was met or not.

Syntax:

public boolean removeIf(Predicate<? super E> filter)

Parameter: This method takes a parameter filter which represents a predicate which returns true for elements to be removed.

Returns: This method returns True if predicate returns true and some elements were removed.

Exception: This method throws NullPointerException if the specified filter is null.

Below programs illustrate removeIf() method of Vector:

Example 1: To demonstrate removeIf() method on vector which contains a set of Numbers and only the numbers which are divisible by 2 will be removed.

// Java Program Demonstrate removeIf()
// method of Vector

import java.util.*;

public class GFG {
    public static void main(String[] args)
    {

        // create an Vector which going to
        // contains a list of Numbers
        Vector<Integer> Numbers = new Vector<Integer>();

        // Add Number to list
        Numbers.add(22);
        Numbers.add(33);
        Numbers.add(55);
        Numbers.add(62);

        // apply removeIf() method
        // to remove numbers divisible by 2
        Numbers.removeIf(n -> (n % 2 == 0));

        System.out.println("All Numbers not divisible by 2 are:");

        // print list
        for (int i : Numbers) {
            System.out.println(i);
        }
    }
}

Output:

All Numbers not divisible by 2 are:
33
55

Example 2: To demonstrate removeIf() method on Vector which contains set of Students Names and to remove all 4 char long name.

// Java Program Demonstrate removeIf()
// method of Vector

import java.util.*;

public class GFG {
    public static void main(String[] args)
    {

        // create a Vector
        // containing a list of string values
        Vector<String> students = new Vector<String>();

        // Add Strings to list
        // each string represents student name
        students.add("Rama");
        students.add("Mohan");
        students.add("Sohan");
        students.add("Rabi");
        students.add("Shabbir");

        // apply removeIf() method
        // to remove names contains 4 chars
        students.removeIf(n -> (n.length() == 4));

        System.out.println("Students name do not contain 4 char are");

        // print list
        for (String str : students) {
            System.out.println(str);
        }
    }
}

Output:

Students name do not contain 4 char are
Mohan
Sohan
Shabbir

Example 3: To demonstrate NullpointerException in removeIf() method on Vector.

// Java Program Demonstrate removeIf()
// method of Vector

import java.util.*;

public class GFG {
    public static void main(String[] args)
    {

        // create a Vector
        // containing a list of string values
        Vector<String> students = new Vector<String>();

        // Add Strings to list
        // each string represents student name
        students.add("Rama");
        students.add("Mohan");
        students.add("Sohan");
        students.add("Rabi");
        students.add("Shabbir");

        try {
            // apply removeIf() method with null filter
            students.removeIf(null);
        }
        catch (Exception e) {
            System.out.println("Exception: " + e);
        }
    }
}

Output:

Exception: java.lang.NullPointerException

Reference: https://docs.oracle.com/javase/8/docs/api/java/util/Vector.html#removeIf-java.util.function.Predicate-