This document discusses the author's first experience using lambda expressions in Java 8. It provides instructions on setting up Java 8 and examples of using lambda expressions for threads, collections, and mapping/reducing streams. Lambda expressions allow passing functionality as arguments to replace anonymous inner classes. The examples demonstrate using lambda expressions for runnables, foreach loops, and mapping/reducing operations. References for further reading on Java 8 lambdas are also included.

1. My First Experience with Lambda
Expressions in Java 8
Tibor Digana

2. What do I need ?
• First of all download and install OpenJDK 1.8
http://jdk8.java.net/lambda/
• Write and compile the following simple code

3. Threads and For-Each in Lambda

4. Overriding run method
• Runnable#run() is anonymous function
• New Thread instance is created
• New Runnable instance is passed to the
constructor of Thread
• run() method calls connectToService()

5. forEach on Collection
• Anonymous function with one parameter
• for-each iterates over given List
• Takes elements and computes their sum
• The sum variable must be final or static

6. Map-Reduce
List<Integer> list = Arrays.asList(1, 2, 3);
int x = list.stream().map(e -> e).reduce(0, (a, b) -> a + b);
• Mapping values of elements 1:1
• Splitting the collection to two parties
• Splitting parties again, etc.
• Computing the SUM on each party
• Reducing their sub-results in the final result

7. Anonymous Function without
parameters is Runnable Object
run(Runnable... blocks) {…}
……
run( () -> { System.out.println("first..."); },
() -> { System.out.println("second..."); }
);
• Passing functionality/task to a thread pool
• Simple when assigning Runnable r = () -> {…};
• Simply registering a listener #addListener( ()-> {…} )
• No need to write anonymous class with one method

8. References
• http://stackoverflow.com/questions/10332402/cant-get-lambdas-to-compile-in-netbeans-7-1-1jdk8-jdk-8-ea-bin-b35
• http://jdk8.java.net/lambda/
• http://www.javabeat.net/2012/05/enhanced-collections-api-in-java-8-supports-lambda-expressions/
• http://cr.openjdk.java.net/~briangoetz/lambda/lambda-state-4.html