Java 8 Collection removeIf method with code samples

Java 8 has added a new method called removeIf to the Collection interface. You can use this to remove an element from a Collection in Java. In this article, I will be explaining the how this method works.

Edit

What does RemoveIf do?

This method removes an element from the Collection that matches a particular condition. It returns a boolean value which indicates whether some values were removed or not.  The condition to be checked is specified via a Predicate instance. Predicate is an in-built functional interface that accepts an argument of any data type and returns a boolean.  You can implement it via a lambda expression.

RemoveIf Integer Code Sample

The following code demonstrates this method on an Integer List:

public class RemoveIfDemo {  public static void main(String[] args) {    List<Integer> input = new ArrayList<Integer>();    input.add(5);    input.add(12);    input.add(17);    input.add(18);    input.add(25);        boolean anyElementRemoved = input.removeIf(num -> (num%2==0));    if(anyElementRemoved){      System.out.println("Elements were removed");      input.forEach(num -> System.out.println(num));    }    else      System.out.println("Elements were not removed");  }}

This code creates an Integer List input with some values. It then invokes the removeIf method on input with a lambda expression that checks if a number is even. So the code applies this lambda expression to each element in the list and the removes the even numbers.  So when you execute this code, it prints the following output to the console:

Elements were removed51725

RemoveIf String Code Sample

The following code demonstrates this method on a String List:

public class RemoveIfStringDemo {  public static void main(String[] args) {    List<String> input = new ArrayList<String>();    input.add("March");    input.add("January");    input.add("September");    input.add("December");        boolean elementsRemoved = input.removeIf(str -> str.endsWith("day"));    if(elementsRemoved){      System.out.println("Elements were removed");      input.forEach(str -> System.out.println(str));    }    else      System.out.println("Elements were not removed");  }}

This code creates a String list input with some String values. It then invokes the removeIf method on input with a lambda expression that checks if a String ends with “day”.  Since there are no strings in the input list that match this condition, no values are removed from input and the removeIf method returns a false. So when you execute this code, it prints the following output:

Elements were not removed

Conclusion

So in this article, you saw how to use the Java 8 Collection.removeIf method to remove an object from an ArrayList. We saw code samples that remove a value from an Integer List and from a String List.

Comments

Post a Comment

Popular posts from this blog

How to use logging in SpringBoot with code samples

Image
In this article, we will learn how to use logging in SpringBoot. Introduction There are several Java logging frameworks like logback, log4j, and so on. Spring Boot supports out-of-the-box support for logback. Let us learn how to use logging in SpringBoot with logback. Step 1 – Create a New Maven Project Create a new Maven project. (Refer to  this  blog post). This will create a project in Eclipse as follows:   Step 2 – Add the Spring Boot Dependencies Add the spring-boot-starter-web dependency to the pom.xml . So, the pom.xml should look as follows: <project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd"> <modelVersion>4.0.0</modelVersion> <groupId>com.learnjava</groupId> <artifactId>learnjava-springboot-logging-example</artifactId> <version>0.0.1-SNAPSHOT&
Read more

Python While Loop with code samples

Much like a Java while loop, you can use a Python while loop to repeatedly execute a block of code as long as a condition is true. In this article, we will learn more about the Python while loop. Python While loop Syntax A while loop in Python has the following syntax: while <condition>: loop body The while keyword is followed by a condition. If the condition evaluates to true, the body of the loop is executed. Once the body of the loop is completed, the condition is checked again and this is repeated until the condition evaluates to false at which point the loop is exited. While loop Sample Code The following code demonstrates how you can use the while loop: num=10counter=1total=0while counter<=num: total += counter counter+=1print("sum of first 10 numbers is",total) This code adds the numbers from 1 to 10 and prints the sum. It uses a while loop to iterate from 1 to 10. The while loop checks the condition counter <= num and if so adds the current value of count
Read more

How to convert a List to a Set

In this blog post ,I will be showing you how you can convert a List to a Set. Consider the following code snippet: public class ListToSetDemo {public static void main(String[] args) {List<Integer> list = Arrays.asList(5,3,11,15,9);//Method 1Set<Integer> set = new HashSet<Integer>(list);System.out.println("Set is "+set);//method 2Set<Integer> set2 = new HashSet<Integer>();set2.addAll(list);System.out.println("Set is "+set2);}} This code demonstrates two ways to convert a List to a Set. Method 1 Here, we are creating a new HashSet . We are invoking the constructor that accepts a Collection object. Here, we are passing in the input list to this constructor.   Method 2 Here again, we are creating a new HashSet . However, we are using the default constructor. We are then invoking the addAll method and passing in the input list.   When you run this code, it will print the following output: Set is [3, 5, 9, 11, 15]Set is [3, 5, 9, 11, 15] No
Read more