4. Deadlock
Deadlock is a phenomenon where two threads attempt to acquire two different objects’ locks which can never be released because the locks are being
acquired by the other thread. This is well-known concept, I just put a code where deadlocks can be occurred, if you can detect
the sequences the deadlock can occur, you already grasped this concept well. Supposed we create two object
Friendly, assigned their partners, and call hug of each object on each thread:
class Friendly {
private Friendly partner;
private String name;
public Friendly(String name) {
this.name = name;
}
public synchronized void hug() {
System.out.println(
Thread.currentThread().getName()+
" in " + name + ".hug() trying to invoke " +
partner.name + ".hugBack()"
);
partner.hugBack();
}
private synchronized void hugBack() {
System.out.println(
Thread.currentThread().getName()+
" in " + name + ".hugBack()"
);
}
public void becomeFriend(Friendly partner) {
this.partner = partner;
}
}