Threads synchronizing in Java, IllegalMonitorStateException
I am trying to synchronize two threads - the "Main" thread, and a runnable. I get the IllegalMonitorStateException, but I do not completelty understand what "you do not have the lock of the object" means.
Here is my code:
public class ThreadsTest {
private static ThreadsTest instance;
public volatile boolean flag = false;
public void doStuff() {
System.out.println("first");
this.flag = true;
}
public Runnable mDrawer = new Runnable() {
public void run() {
synchronized (ThreadsTest.getInstance()) {
while (flag == false)
try {
wait();
} catch (InterruptedException ie) {
System.out.println("second");
}
}
}
};
public static ThreadsTest getInstance() {
if (ThreadsTest.instance == null) {
ThreadsTest.instance = new ThreadsTest();
}
return ThreadsTest.inst开发者_如何学JAVAance;
}
private ThreadsTest() {
}
public static void main(String[] args) {
ThreadsTest t = ThreadsTest.getInstance();
t.mDrawer.run();
t.doStuff();
}
}
You may call wait()
method only on objects you synchronizing on.
So, since you have synchronized (ThreadsTest.getInstance())
, you must write ThreadsTest.getInstance().wait()
.
Not sure what you trying to test here exactly, if it's just basic thread sync sample, then you should change your code to
public class ThreadsTest {
private static ThreadsTest instance;
public volatile boolean flag = false;
public void doStuff() {
System.out.println("first");
this.flag = true;
synchronized (getInstance()) {
getInstance().notifyAll();
}
}
public Runnable mDrawer = new Runnable() {
public void run() {
synchronized (ThreadsTest.getInstance()) {
while (flag == false)
try {
ThreadsTest.getInstance().wait();
} catch (InterruptedException ie) {
System.out.println("second");
}
}
}
};
public static ThreadsTest getInstance() {
if (ThreadsTest.instance == null) {
ThreadsTest.instance = new ThreadsTest();
}
return ThreadsTest.instance;
}
private ThreadsTest() {
}
public static void main(String[] args) throws InterruptedException {
ThreadsTest t = ThreadsTest.getInstance();
new Thread(t.mDrawer).start();
Thread.sleep(1000L); // let other thread start, so it won't skip our notify()
t.doStuff();
}
}
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