Java8: removeIf example

'java.util.Collection' class provides 'removeIf' method to remove all the elements of this collection that satisfy the given predicate. This method returns true, if any element is removed from the collection.

The definition of ‘removeIf’ method looks like below.

    default boolean removeIf(Predicate<? super E> filter) {

        Objects.requireNonNull(filter);

        boolean removed = false;

        final Iterator<E> each = iterator();

        while (each.hasNext()) {

            if (filter.test(each.next())) {

                each.remove();

                removed = true;

            }

        }

        return removed;

    }

        

As you see above snippet, removeIf method uses the collection iterator to traverse the elements. If the element matches to the predicate, then it is removed from the collection using iterator 'remove' method. If iterator do not support removal of elements, then UnsupportedOperationException is thrown.

Find the below working example.

Employee.java

package com.sample.app.model;

public class Employee {
 private int id;
 private String firstName;
 private String lastName;

 public Employee(int id, String firstName, String lastName) {
  this.id = id;
  this.firstName = firstName;
  this.lastName = lastName;
 }

 public int getId() {
  return id;
 }

 public void setId(int id) {
  this.id = id;
 }

 public String getFirstName() {
  return firstName;
 }

 public void setFirstName(String firstName) {
  this.firstName = firstName;
 }

 public String getLastName() {
  return lastName;
 }

 public void setLastName(String lastName) {
  this.lastName = lastName;
 }

 @Override
 public String toString() {
  return "Employee [id=" + id + ", firstName=" + firstName + ", lastName=" + lastName + "]";
 }

}

Test.java

package com.sample.app;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

import com.sample.app.model.Employee;

public class Test {

 private static List<Employee> emps = new ArrayList<>();

 static {
  loadEmployees();
 }

 private static void loadEmployees() {
  Employee emp1 = new Employee(1, "Krishna", "Gurram");
  Employee emp2 = new Employee(2, "Joel", "Chelli");
  Employee emp3 = new Employee(3, "Gopi", "Battu");
  Employee emp4 = new Employee(4, "Janaki", "Sriram");
  Employee emp5 = new Employee(5, "Janaki", "Maj");

  emps.addAll(Arrays.asList(emp1, emp2, emp3, emp4, emp5));
 }

 private static void printEmployees() {
  emps.stream().forEach(System.out::println);
 }

 public static void main(String args[]) {
  printEmployees();

  System.out.println("\nRemove all employees with even ids\n");

  /* Remove employees with even number ids */
  boolean isEmpsRemoved = emps.removeIf(emp -> emp.getId() % 2 == 0);

  System.out.println("Is employees removed : " + isEmpsRemoved + "\n");

  printEmployees();

 }
}

Run Test.java, you can able to see below messages in console.

Employee [id=1, firstName=Krishna, lastName=Gurram]
Employee [id=2, firstName=Joel, lastName=Chelli]
Employee [id=3, firstName=Gopi, lastName=Battu]
Employee [id=4, firstName=Janaki, lastName=Sriram]
Employee [id=5, firstName=Janaki, lastName=Maj]

Remove all employees with even ids

Is employees removed : true

Employee [id=1, firstName=Krishna, lastName=Gurram]
Employee [id=3, firstName=Gopi, lastName=Battu]
Employee [id=5, firstName=Janaki, lastName=Maj]

Previous                                                 Next                                                 Home