1. package Paradigms.List11.CommonStaticVariableResolvings;
2.  
3.  
4.  
5. public class IntCellMonitor {
6.  
7.     // function sets isSet on false and on the beggining checks
8.  
9.     // if isSet is false then stops the execution of the thread until another thread invokes the notify
10.  
11.     // then condition is checked one more time
12.  
13.     // it prevents from read the same value by two threads until first thread will call set function
14.  
15.     // the same history with set
16.  
17.     public synchronized int getN(){
18.  
19.         while(!isSet){
20.  
21.             waitForNotifying();
22.  
23.         }
24.  
25.         isSet=false;
26.  
27.         notifyAll();
28.  
29.         // Wakes up all threads that are waiting on this object's monitor
30.  
31.         return n;
32.  
33.     }
34.  
35.  
36.  
37.     // function sets isSet on true and on the beggining checks
38.  
39.     // if isSet is true then stops the execution of the thread until another thread invokes the notify
40.  
41.     // then condition is checked one more time
42.  
43.     // it prevents from set the same value by two threads until first thread will call get function
44.  
45.     // the same history with set
46.  
47.     public synchronized void setN(int n){
48.  
49.         while(isSet){
50.  
51.             waitForNotifying();
52.  
53.         }
54.  
55.         this.n = n;
56.  
57.         isSet = true;
58.  
59.         notifyAll();
60.  
61.     }
62.  
63.  
64.  
65.     // above approach protects from the replicated call of getN or setN between threads
66.  
67.     // it forces to call getN before setN everytime
68.  
69.     private void waitForNotifying(){
70.  
71.         try{
72.  
73.             wait();
74.  
75.             // causes the current thread to wait until
76.  
77.             // another thread invokes the notify/notifyAll() method for this obj
78.  
79.         }catch(InterruptedException e){
80.  
81.             e.printStackTrace();
82.  
83.         }
84.  
85.     }
86.  
87.  
88.  
89.     private boolean isSet = true;
90.  
91.     private int n = 0;
92.  
93. }
94.  
95.  
96.  
97. class CountMonitor extends Thread{
98.  
99.     static IntCellMonitor n = new IntCellMonitor();
100.  
101.  
102.  
103.     @Override
104.  
105.     public void run(){
106.  
107.         for (int i = 0; i < 200000; i++){
108.  
109.             int temp = n.getN();
110.  
111.             n.setN(temp+1);
112.  
113.         }
114.  
115.     }
116.  
117.  
118.  
119.     public static void main(String[] args){
120.  
121.         CountMonitor thread1 = new CountMonitor();
122.  
123.         CountMonitor thread2 = new CountMonitor();
124.  
125.         thread1.start();
126.  
127.         thread2.start();
128.  
129.         try{
130.  
131.             thread1.join();
132.  
133.             thread2.join();
134.  
135.         }catch(InterruptedException e){
136.  
137.             System.out.println(e.getStackTrace());
138.  
139.             System.out.println("Catched exception");
140.  
141.         }
142.  
143.         System.out.println("The value of n is " + n.getN());
144.  
145.         System.out.println("Monitor edition");
146.  
147.     }
148.  
149. }