Lambda Expressions Before And AfterJava 8


Quick guide to few example programs on before and after Java 8. Java 8 Concepts further simplifies the code and profound for core logic rather than syntax.

1. Introduction

In this tutorial, We'll learn how to write programs using java 8 lambda and Stream concepts with examples. Many developers feel learning java 8 concepts may be hard to understand. But once we are good using them then feel reduces error prone code and improves the performance of the application.

Read article on Java 8 Lamda Expression Rules

Examples Programs Before and After Java 8

In this article, We will see the example programs on sorting using Comparator, File names validation, Retrieving only hidden files and filtering list objects based on conditions.

2. Sorting - Lambda Expression

2.1 Before Java 8

See the below code which is implemented in older versions of Java. Here trying to sort the Employee's based on the id column.

Collections.sort(emplyeesList, new Comparator() {
 public int compare(Employee a1, Employee a2){
  return a1.getId().compareTo(a2.getId());

Here, written code in 5 lines in which includes Comparator implementation.

2.2 In Java 8

See the below code in Java 8. All the code is in single line and not seeing comparing logic.


Here, Comparator is a Functional Interface which has only one abstract method.

Comparator has a static method comparing(.Function.) which accepts only Funtion interface.

Note: Function<T, R> also a Functional Interface. This has a method apply(T t) which will be called from Comparator.comparing() method.

3. File Name Validation with Lambda Expression

3.1 Before Java 8

See the code in java old version. Here the core logic is file.getName().endsWith(".xml"); The remaining code is just syntax.

File[] hiddenFiles = new File("directory_name").listFiles(new FileFilter() {
 public boolean accept(File file) {
  return file.getName().endsWith(".xml");

3.2 In Java 8

The above code is simplified to single line which reduces the errors.

File[] hiddenFiles = new File("directory_name").listFiles( file -> file.getName().endsWith(".xml"));

Note: Java 8, just focus on the business logic and takes its syntax internally. Developer need not to worry about it.

4. Retrieving only Hidden files - Lambda Expression

4.1 Before java 8

File has a method to check the method is hidden or not using isHidden() method.

File[] hiddenFiles = new File("directory_name").listFiles(new FileFilter() {
 public boolean accept(File file) {
  return file.isHidden();

4.2 In Java 8

Just using the new Method Reference concept as part of new Java 8.

File[] hiddenFiles = new File("directory_name").listFiles(File::isHidden);

5. Conclusion

In this post, We've seen example lambda program before and after Java 8.

Observed the differences between them. Java 8 were in many ways more profound than any other changes to Java in its history.



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Author: Venkatesh - I love to learn and share the technical stuff.

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JavaProgramTo.com: Lambda Expressions Before And AfterJava 8
Lambda Expressions Before And AfterJava 8
Quick guide to few example programs on before and after Java 8. Java 8 Concepts further simplifies the code and profound for core logic rather than syntax.
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