multithreading - Java Thread inter process communication working in boolean variable condition but not in int? -

i have code communicating 2 threads in jre6. when run following program expected output come like,
a: hi
b: hi
a: how r u?
b: im fine wat u?
a: i'm fine
b: me too

class chat {      boolean flag = false;      public synchronized void gettalk1(string msg) throws interruptedexception {         if (flag) {             wait();         }         system.out.println(msg);         flag = true;         notify();     }      public synchronized void gettalk2(string msg) throws interruptedexception {         if (!flag) {             wait();         }         system.out.println(msg);         flag = false;         notify();     } }  class thread1 extends thread {     chat chat;      public thread1(chat chat) {         this.chat = chat;     }      string[] talk = { "hi", "how r u?", "i'm fine" };      @override     public void run() {         (int = 0; < talk.length; i++) {             try {                 chat.gettalk1("a: " + talk[i]);             } catch (interruptedexception e) {                 e.printstacktrace();             }         }     } }  class thread2 extends thread {     chat chat;      public thread2(chat chat) {         this.chat = chat;     }      string[] talk = { "hi", "im fine wat u?", "me too" };      @override     public void run() {         (int = 0; < talk.length; i++) {             try {                 chat.gettalk2("b: " + talk[i]);             } catch (interruptedexception e) {                 e.printstacktrace();             }         }     } }  public class conversation {     public static void main(string[] args) {         chat chat = new chat();         new thread1(chat).start();         new thread2(chat).start();     } } 

but when change chat class flag variable boolean int type

class chat {      volatile int flag = 2;         public synchronized void gettalk1(string msg) throws interruptedexception {         if (flag == 1) {             wait();         }         system.out.println(msg);         flag = 2;         notify();     }      public synchronized void gettalk2(string msg) throws interruptedexception {         if (flag == 2) {             wait();         }         system.out.println(msg);         flag = 1;         notify();     } } 

the output varied , executing not stop
a: hi
a: how r u?
a: i'm fine
...still running

what reason?

compare

    if (flag) {         wait();     }     system.out.println(msg);     flag = true;     notify(); 

with

    if (flag == 1) {         wait();     }     system.out.println(msg);     flag = 2;     notify(); 

in first case, wait if flag == true , set flag = true. in second case, wait if flag == 1 , set flag = 2. logic inverted.