multithreading - java, why thread.wait() don't work in my code -


i have screenplay(thread) print several pieces of texts circularly，and there screenbreak print urgent texts, , when screenbreak prints, should wait screenplay first. after screenbreak print texts, notify screenplay, , screenplay begin printing.

class screenplay implements runnable{      public synchronized void notifys() throws interruptedexception {       notify();     }      public synchronized void waits() throws interruptedexception {       wait();     }      public void run(){       for(int i=0; i<15; i++){              system.out.println(i);           try{             thread.sleep(500);            }catch(interruptedexception e){             e.printstacktrace();           }           if( == 14 ){               = -1;           }       }     } }  class screenbreak implements runnable{   private screenplay screenplay;    public screenbreak(screenplay screenplay){     this.screenplay = screenplay;   }    public void run(){     try{       thread.sleep(2000);       screenplay.waits();     }catch(interruptedexception e){       e.printstacktrace();     }     for(int i=0; i<5; i++){       system.out.println("@_" + i);     }     try{       thread.sleep(5000);       screenplay.notifys();     }catch(interruptedexception e){       e.printstacktrace();     }   }  }  public class waits {     public static void main(string[] args) {        screenplay s = new screenplay();       screenbreak sb = new screenbreak(s);       new thread(s).start();       new thread(sb).start();      } }

the output shows 'wait()' don't work @ all, screenplay continues print. screenbreak never print texts. why? wrong here?

i modify code , works.

class screenplay implements runnable{      private int waittime = 1050;     private boolean ispause = false;      public synchronized  void setispause(boolean ispause){       this.ispause = ispause;     }      public synchronized void go() throws interruptedexception {       this.ispause = false;       notify();     }      public void run(){       for(int i=0; i<15; i++){              system.out.println(i);           try{             for(int j = 0; j < waittime/500 + 1; j++){               thread.sleep(500);                synchronized(this){                 if(ispause){                   system.out.println("waiting");                  wait();                 }else{                   system.out.println("...");                  }               }             }           }catch(interruptedexception e){             e.printstacktrace();           }           if( == 14 ){               = -1;           }       }     } }  class screenbreak implements runnable{   private screenplay screenplay;    public screenbreak(screenplay screenplay){     this.screenplay = screenplay;   }    public void run(){     try{       thread.sleep(2000);     }catch(interruptedexception e){       e.printstacktrace();     }      screenplay.setispause(true);     try{       thread.sleep(5000);       for(int i=0; i<5; i++){           system.out.println("@_" + i);       }       screenplay.go();     }catch(interruptedexception e){       e.printstacktrace();     }    }  }  public class waits {     public static void main(string[] args) {        screenplay s = new screenplay();       screenbreak sb = new screenbreak(s);       new thread(s).start();       new thread(sb).start();       try{         thread.sleep(15000);       }catch(interruptedexception e){         e.printstacktrace();       }       new thread(sb).start();      } }

when screenbreak starts wait()ing, there's nobody notify() it. call notify() in screenbreak, it'll never there since it's stuck @ wait().

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