java 线程同步 synchronized

Question

public class Test {

private int i = 0;

public Test() {

}

public int getI() {
    return i;
}

public void setI(int i) {
    this.i = i;
}

public static void main(String[] args) throws InterruptedException {
    Test t = new Test();
    Thread tt1 = new Thread(new TestThread(t));
    Thread tt2 = new Thread(new TestThread(t));
    Thread tt3 = new Thread(new TestThread(t));
    Thread tt4 = new Thread(new TestThread(t));
    tt1.start();
    tt2.start();
    tt3.start();
    tt4.start();
    tt1.join();
    tt2.join();
    tt3.join();
    tt4.join();
    System.out.println("ok");
}

}

public class TestThread implements Runnable {

Test t;

public TestThread (Test t) {
    this.t = t;
}

public synchronized void run() {
    t.setI(t.getI() + 10);
    System.out.println(t.getI());
}

}

 输出：
30
30
40
40
ok

问题 ：
想要得到输出10 20 30 40，为什么加了synchronized还不行

Answer 1

 public  void run() {
    synchronized(t){
        t.setI(t.getI() + 10);
        System.out.println(t.getI());
    }
}