Threads

A thread is an independent sequential path of execution within a program. Many threads can run concurrently within a program. At runtime, threads in a program exist in a common memory space and can, therefore, share both data and code, that is, they are lightweight compared to processes. They also share the process running the program.

Every thread in Java is created and controlled by a unique object of the java.lang.Thread class. Often the thread and its associated Thread object are thought of as being synonymous.

The Main Thread

The runtime environment distinguishes between user threads and daemon threads. As long as a user thread is alive, the JVM does not terminate. A daemon thread is at the mercy of the runtime system: it is stopped if there are no more user threads running, thus terminating the program. Daemon threads exist only to serve user threads

Thread Creation

A thread in Java is represented by an object of the Thread class. Implementing threads is achieved in one of two ways:

• implementing the java.lang.Runnable interface

• extending the java.lang.Thread class