Thread Creation
In this chapter you will learn:
Two ways to create a thread
Java defines two ways in which this can be accomplished:
- You can implement the Runnable interface.
- You can extend the Thread class, itself.
Implementing Runnable
To implement Runnable, a class need only implement
a single method called run(), which is declared like this:
void run();
Inside run(), you will define the code that constitutes
the new thread.
run() establishes the entry point for another,
concurrent thread of execution within your program.
This thread will end when run() returns.
After you create a class that implements Runnable,
you will instantiate an object of type
Thread from within that class. Thread defines several constructors.
After the new thread is created, it will not start running until you call its start() method.
start() executes a call to run().
class NewThread implements Runnable {
Thread t;/*from j av a 2 s .c om*/
NewThread() {
t = new Thread(this, "Demo Thread");
System.out.println("Child thread: " + t);
t.start(); // Start the thread
}
public void run() {
try {
for (int i = 5; i > 0; i--) {
System.out.println("Child Thread: " + i);
Thread.sleep(500);
}
} catch (InterruptedException e) {
System.out.println("Child interrupted.");
}
System.out.println("Exiting child thread.");
}
}
public class Main {
public static void main(String args[]) {
new NewThread(); // create a new thread
try {
for (int i = 5; i > 0; i--) {
System.out.println("Main Thread: " + i);
Thread.sleep(1000);
}
} catch (InterruptedException e) {
System.out.println("Main thread interrupted.");
}
System.out.println("Main thread exiting.");
}
}
Extending Thread
The extending class must override the run() method,
which is the entry point for the new thread.
It must also call start() to begin execution of the new thread.
Here is the preceding program rewritten to extend Thread:
class NewThread extends Thread {
NewThread() {// j a v a 2 s.com
super("Demo Thread");
System.out.println("Child thread: " + this);
start(); // Start the thread
}
public void run() {
try {
for (int i = 5; i > 0; i--) {
System.out.println("Child Thread: " + i);
Thread.sleep(500);
}
} catch (InterruptedException e) {
System.out.println("Child interrupted.");
}
System.out.println("Exiting child thread.");
}
}
public class Main {
public static void main(String args[]) {
new NewThread(); // create a new thread
try {
for (int i = 5; i > 0; i--) {
System.out.println("Main Thread: " + i);
Thread.sleep(1000);
}
} catch (InterruptedException e) {
System.out.println("Main thread interrupted.");
}
System.out.println("Main thread exiting.");
}
}
Next chapter...
What you will learn in the next chapter: