Thread Synchronization

[Garg Amit]

Please help me to explain below code. As per my understanding this should be a deadlock condition.

Source of this example(U-certify question Bank)

public class CheckNeavigableCode {
public static void main(String ar[]) throws InterruptedException {
String str1 = new String("R1");
String str2 = new String("R2");
MyThread thrd1 = new MyThread("Firsr", str1, str2);
MyThread thrd2 = new MyThread("Second", str1, str2);
thrd1.start();
thrd1.join();
thrd2.start();
}
}

class MyThread extends Thread {
private String First;
private String Second;

public MyThread(String thrdname, String one, String two) {
super(thrdname);
First = one;
Second = two;
}

public void run() {
if (getName().equals("First")) {
synchronized (First) {
try {
Thread.sleep(4000);
} catch (InterruptedException E) {
E.printStackTrace();
}
synchronized (Second) {
}
}
} else {
synchronized (Second) {
try {
Thread.sleep(4000);
} catch (InterruptedException E) {
E.printStackTrace();
}
synchronized (First) {
}
}
}
}
}

[Henry Wong]

thrd1.start(); 
thrd1.join(); 
thrd2.start(); 

The main thread starts thread 1, then it waits for thread 1 to finish, then it starts thread 2. The two threads are never running concurrently.

Henry

[Garg Amit]

Thanks for reply.

Without thrd1.join(); would it be a deadlock?

[Sanju Thomas]

yep.

[Sanju Thomas]

if you change the line given below

MyThread thrd1 = new MyThread("Firsr", str1, str2);

to

MyThread thrd1 = new MyThread("First", str1, str2);

then it should create a dead lock.