From this page (Java Monitors Are Reentrant) there's a sentence that says:Reentrant contains two synchronized methods: a and b. The first  synchronized method, a, calls the other synchronized method, b.When control enters method a, the current thread acquires the monitor  for the Reentrant object.What does the control refer to in the sentence control enters method a? 
Control enters method a What does control mean in this context?
terminology
Control is The place where the next instruction is going to be executed.  If you are familiar with Assembly Language, you can think of it as the value contained in the Program Counter register.The term comes from the notion Flow of Control, the specific order in which statements are executed to produce a computing result.So when someone says that Control enters method A, it means that method A is about to be executed.  Or, more specifically, the instructions or statements in method A are about to be executed.  