/*

  TestUnsafe class, which extends Thread, and runs through one BankAcct 

  object, and displays the balance as its running.

*/

public class TestUnsafe extends Thread{

    //data members for this thread

    private String name;

    BankAcct ba;



    //start this method

    public static void main( String[] args ){

        BankAcct ba = new BankAcct( 0 );

        new TestUnsafe( "**      " , ba ).start();

        new TestUnsafe( "  ++    " , ba).start();

        new TestUnsafe( "    ==  " , ba ).start();

        new TestUnsafe( "      //" , ba ).start();

    }

    

    //constructor

    public TestUnsafe( String n , BankAcct ba ){

        this.ba = ba;

        name    = n;

    }



    //extending Thread

    public  void run(){

        doWork();

    }



    //simply displays the bank balance before and after this thread

    //messes with the bankaccount

    public void doWork(){

        System.out.println( name+" :doWork() - start : account bal = "+ba.get() );

        

        ba.doNothing();



        System.out.println( name+" :doWork() - end   : account bal = "+ba.get() );

    }

    



}//end TestUnsafe class





/*

  BankAcct is the thread-unsafe class that should do nothing (by 

  adding and then removing money from the balance). However, the 

  Test thread messes up the BankAcct balance as a bunch of them

  trample through this object.

*/

class BankAcct{

    int bal;



    public BankAcct( int i ){

        bal = i;

    }



     void doNothing(){

        addRemove( 10 );

        addRemove( 20 );

        addRemove( 30 );

    }



     void addRemove( int m ){

        bal+=m;

        Util.sleepRandom();

        bal-=m;

    }



     int get(){

        return bal;

    }

}//end BankAcct class





class Util{

  //this method simply puts whatever thread that's running through

  //the code to sleep for a random number of milliseconds.

  public static void sleepRandom(){



      try{

          Thread.currentThread().sleep( (long)(Math.random()*100) );

      }

      catch(Exception e){

        System.out.println( e );

      }                      



  }



}//end Util class