How to configure Java 8 in Eclipse IDE

First you will need to download the following prerequisites (if you haven't already):

1. Download the Java 8 JDK/JRE from Oracle download website
2. Download Eclipse Kepler or later (in this article I have used Kepler 4.3.2 version with the required Java 8 patches already included)

After downloading both items above you may launch Eclipse IDE.

After launching Eclipse go through the following menu entries:

Window -> Preferences -> Java -> Installed JREs

Now click on Add... and set JRE home field with the path to your Java 8 JDK/JRE installation directory.

In order to configure the Java 8 compiler go through the following menu entries:

Window -> Preferences -> Java -> Compiler

Now change JDK compiler compliance level to 1.8

Now that everything is ready, we may create a sample project containing the following test class:

package com.byteslounge.test;

public class Test {

  public static void main(String args[]){
    int x = new Test().sum(1, 3, (int a, int b) -> a + b); 
    System.out.println("Result: " + x);
  }
  
  private int sum(int a, int b, TestInterface testInterface){
    return testInterface.sum(a, b);
  }
  
  private interface TestInterface {
    int sum(int a, int b);
  }
  
}

We are using a lambda expression in our class. Eclipse will successfully compile and run our test class, and produce the expected output:

• Java 8 Date Time API
• Java 8 Collect
• Java 8 Reduction
• Java 8 Parallel Streams