Ivor Horton's Beginning Java®, Java 7 Edition

Chapter 16

Threads

WHAT YOU WILL LEARN IN THIS CHAPTER

• What a thread is and how to create threads in your programs
• How to control interactions between threads
• What synchronization means and how to apply it in your code
• What deadlocks are and how to avoid them
• What an executor is and how to use an executor to start and manage threads
• How to create threads that return a value
• How to set thread priorities

In this chapter you investigate the Java facilities that enable you to overlap the execution of segments of a single program. As well as ensuring your programs run more efficiently, this capability is particularly useful when your program must, of necessity, do a number of things at the same time: for example, a server program on a network that needs to communicate with multiple clients. As you see in Chapter 18, threads are also fundamental to any Java application that uses a graphical user interface (GUI), so it’s essential that you understand how threads work.

UNDERSTANDING THREADS

Most programs of a reasonably large size contain some code segments that are more or less independent of one another and that might execute more efficiently if the code segments could be overlapped in time. Threads provide a way to do this. A thread of execution is a serial sequence of instructions that is reasonably independent of other code segments in a program so its execution can be controlled independently. If you have a machine with two or more processors then as many computations as you have ...