1. What does Thread.currentThread() do?

It returns a reference to the currently executing thread — the thread that is calling this method.

Thread t = Thread.currentThread();
System.out.println(t.getName());

If the current thread’s name is “main”, it will print “main”. It tells: “Who is running this code right now?“

2. Why does it have to be a static method?

Because you don’t already have an instance of the current thread when you want to ask:

• You cannot call an instance method like this.currentThread() because you don’t have an instance yet.
• If it was a non-static method, you would need to already know which thread object you are in — but that’s exactly the thing you are trying to find out.

Therefore, it must be static, because you are asking the Thread class itself:

In simple words, You need a way to access the current thread without already having a thread object.

3. What would happen if it was not static?

If currentThread() were non-static:

• You would need an object to call it on.
• But you don’t have the object yet — you need to discover it.
• It would cause a paradox: “You need the current thread to get the current thread.”

So static solves this neatly — you don’t need an object; you ask the class directly.