Why does it say that "'synchronized(this)' isn't suitable here", if we must use it to pass the task?

Question about the task

A wise man thinks once before speaking twice

Java Multithreading, Level 6, Lesson 8

Under discussion

This code was verified, so what I didn't get?

public int getSumOfVar1AndVar2() {
    synchronized (this) {
        return var1 + var2;
    }
}

public int getSumOfVar3AndVar4() {
    synchronized (Solution.class) {
        return var3 + var4;
    }
}

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Darek

Level 41 , Katowice, Poland

5 October 2020, 12:13

In the post below Guadalupe Gagnon excellently replied why this is a bad choice. I propose: 1. set up two different objects that will have private and fanal modifiers e.g. private final Object obj1 = new Object (); private final Object obj2 = new Object (); 2. In each method, you only use one object and synchronize with the block. synchronized (obj1) {return var1 + var2;} It does not use the same object for both methods. Then the situation will be the same as Guadalupe Gagnon described it wonderfully