Raymond Yang

Introduction:

Lambda is a magic expression in Java 8, which makes tens or hundreds of lines become one line, and makes code concise and easy. This post will introduce using lambda expression for thread pool and stream.

Thread pool lambda expression

Recently I am using Java thread pool, and Mateusz reminds me to try lambda expression. It really opens a new world to me. Instead of implementing another class implements runnable (or extends thread), I can use one line to express everything.

Here let’s see a short example I write.

// Create 5 threads in pool
ExecutorService executor = Executors.newFixedThreadPool(5);

Runnable task = () -> {
    String threadName = Thread.currentThread().getName();
    System.out.println("The current thread is " + threadName);
}

executor.submit(task);

One awesome point using Lambda expression is that we don’t need to create another class for thread, which means we don’t need pass a lot of parameter and construct the class.

If you want to see the thread execution result, you can also use a Future object to get the thread execution result;

Future<String[]> future = executor.submit(task);
System.out.println("The execution of thread 0 is " + future.get()[0]);

Stream

I am not going to talk about the inputstream. Instead, using stream to manipulate list is another awesome lambda expression in Java 8.

List<String> list = Arrays.asList("e1", "e2", "e3");

list.stream()
    .filter(s -> s.contains("1"))
    .map(String::toUpperCase)

// Out
E1

It’s similar the list operation in Perl.

Anyway, Java 8 is more powerful than ever. I do see it learns a lot powerful strength from other language. Still remember how exhausting to write a thread class, now with Lambda expression, everything is becoming so concise and beautiful.