os_critical_section_solution.java

public class OS_Critical_Section_Solution {
	public static void main(String[] args) {
		
		boolean[] flag = new boolean[2]; // flag[0] -> Process A, flag[1] -> Process B
		// Strict Alternation
		int cnt = 0;
		while(true) { 
			flag[0] = true;
			while (flag[1]==true);
			System.out.println("V");
			flag[0] = false;
		}

		// Decker's Algorithm
		// test 1 : Process A gets priority. No stuff for Process B.-> V would be printed continuously.
		boolean turn = false; // turn is false for giving A priority.
		// test 2 : Process A gets priority. Process B gets some stuffs to do -> V not be printed.
		flag[1] = true;
		// test 3 : B is prior to A but gets nothing to proceed -> V would be printed continuously.
		flag[1] = false;
		turn = true;
		while (true) {
			flag[0] = true;
			while (flag[1] == true) {
				if (turn == true) {
					flag[0] = false;
					while(turn == true);
					flag[0] = true;
				}
			};
			System.out.println("V");
			flag[0] = false;
			turn = true; // B gets priority.
		}
		// Peterson's Algorithm
		while (true) {
			flag[0] = true;
			turn = true;
			while (flag[1] && turn); // if B wants to get access in the current critical section and it is prior to all others, Process A could not get in.
			System.out.println("V");
			flag[0] = false;

		}
	}
}