␡
- Motivation
- Basic threads
- Sharing limited resources
- Thread states
- Cooperation between threads
- Deadlock
- The proper way to stop
- Interrupting a blocked thread
- Thread groups
- Summary
- Exercises
This chapter is from the book
This chapter is from the book
This chapter is from the book
This chapter is from the book
Interrupting a blocked thread
There are times when a thread blocks—such as when it is waiting for input—and it cannot poll a flag as it does in the previous example. In these cases, you can use the Thread.interrupt( ) method to break out of the blocked code:
//: c13:Interrupt.java
// Using interrupt() to break out of a blocked thread.
import java.util.*;
class Blocked extends Thread {
public Blocked() {
System.out.println("Starting Blocked");
start();
}
public void run() {
try {
synchronized(this) {
wait(); // Blocks
}
} catch(InterruptedException e) {
System.out.println("Interrupted");
}
System.out.println("Exiting run()");
}
}
public class Interrupt {
static Blocked blocked = new Blocked();
public static void main(String[] args) {
new Timer(true).schedule(new TimerTask() {
public void run() {
System.out.println("Preparing to interrupt");
blocked.interrupt();
blocked = null; // to release it
}
}, 2000); // run() after 2000 milliseconds
}
} ///:~
The wait( ) inside Blocked.run( ) produces the blocked thread. When the Timer runs out, the object's interrupt( ) method is called. Then the blocked reference is set to null so the garbage collector will clean it up (not necessary here, but important in a long-running program).