Threads Critical

Question

How could I change the two classes below so that the
two threads take turns to be in their critical sections,
and they aren't allowed to take two consecutive turns.
Thanks.
public class SharedVariables extends Object {
public int turn;
public boolean[] flag = new boolean[2];
public SharedVariables() {
flag[0] = false;
flag[1] = false;
// A thread running SectionedCode alternates between
// a critical section and the remainder.
public class SectionedCode implements Runnable {
int this_thread, other_thread;
SharedVariables s;
public SectionedCode( int tid, SharedVariables SV ) {
this_thread = tid;
other_thread = 1 - tid;
s = SV;
public void run() {
while ( true ) {
s.flag[this_thread] = true;
s.turn = other_thread;
while ( (s.flag[other_thread] == true) && (s.turn == other_thread) )
Thread.yield();
System.out.printn("Thread "+this_thread+ "incritical section");
s.flag[this_thread] = false;
System.out.println("Thread " + this_thread + " in remainder");
}

Answer 1

Cant it be done without synchronisation?If you created a boolean and a char variable, using the boolean to indicate whether or not the method is in use and the char indicates which thread last used the method, that would work. What you have effectively done is to implement your own version of synchronization. :->
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