What Cases Require Synchronized Method Access in Java?

Question

In what cases is it necessary to synchronize access to instance members? I understand that access to static members of a class always needs to be synchronized- because they

Answer 1

If you want to make this class thread safe I would declare instanceVar as volatile to make sure you get always the most updated value from memory and also I would make the setInstanceVar() synchronized because in the JVM an increment is not an atomic operation.

private volatile int instanceVar =0;

public synchronized setInstanceVar() { instanceVar++;

}