Synchronized qeustion.

Question

Hi,
I a really newbie to JAVA .
I'm trying to understand the meaning of synchronized via an example :
I've created 3 JAVA class :
Stacky
Thread1
Thread2
Thread1 will fill the Stacky .
Thread1 will read from the Stacky .
without the synchronized reserved word I get error - ok , I understand it.
I would expect the synchronized to resolve this problem but it didn't ...
please ... what am I doing wrong ?

Answer 1

My JAVA CODE ....
package Synchronized;
public class Main {
          public static void main (String[] args)
               Stacky stc = new Stacky();
               Thread1 trd1 = new Thread1(stc );
               Thread2 trd2 = new Thread2(stc);
               trd1.start();
               trd2.start();
package Synchronized;
public class Stacky {
     private int top = 0;
     private int data[] = new int[10];
     public void push(int num) {
          /**Try run this code with and without the synchronized command [in the push and in the pop methods]**/
          synchronized(this)
                    System.out.println("Insert " + top);
                    data[top] = num;
                    top++;
     public int pop() {
          /**Try run this code with and without the synchronized command [in the push and in the pop methods]**/
          synchronized(this){
               int temp = --top;
               System.out.println("Get" + temp );
               return data[temp];
package Synchronized;
public class Thread1 extends Thread{
     Stacky stc;
     public Thread1(Stacky s )
          stc = s;
     public void run()
          for (int i = 0; i < 10; i++) {
               stc.push(i);     
               //dummy wait code ...
               try{
                    Thread.sleep(1900);
                    catch(InterruptedException e){
                    System.out.println("Sleep Interrupted");
package Synchronized;
public class Thread2 extends Thread{
     Stacky stc;
     public Thread2(Stacky s )
          stc = s;
     public void run()
          for (int i = 0; i < 10; i++) {
               stc.pop();     
}