Threads

As we have mentioned already, the main application thread can create other - child - threads and let them run in parallel, either sharing the same core via time slicing or having a dedicated CPU for each thread. It can be done using the class java.lang.Thread, which implements the functional interface Runnable. The interface is called functional if it has only one abstract method (we will discuss functional interfaces in Chapter 17, Lambda Expressions and Functional Programming). The Runnable interface contains one method, run().

There are two ways to create a new thread:

• Extend the Thread class
• Implement the Runnable interface and pass the object of the implementation into the constructor of the class Thread

Extending the Thread class

Whatever method is used, we end up with a Thread class object that has the method start(). This method call starts the thread execution. Let's look at an example. Let's create a class called AThread that extends Thread and overrides its run() method:

public...