you need to be the "owner of the object's monitor" to be able to call notify on it. so far your methods are all synchronized(this)
, yet they call notify() on other objects (that they are not synchronized on). in other words:
synchronized(t2) {
t2.notify();
}
and
synchronized(t1) {
t1.notify();
}
for a complete explanation of monitors and synchronization in java, see here, or look for similar questions here on SO, like this one - Java Wait and Notify: IllegalMonitorStateException