CODEWITHSUNDEEP
javamultithreadinggarbage-collection
alan
alan

Reputation: 263

What will happen when a Java thread is set to null?

After a thread started, if the reference of the thread is set to null, what will happen to the thread? Does it stop? Is it eligible for GC?

Like this:

t.start();
t = null;

Upvotes: 26

Views: 7414

Answers (4)

Linkon Ruhul
Linkon Ruhul

Reputation: 105

The thread will be running, its reference is just set to null and thats why it will not be eligible for GC.

Upvotes: 0

MattC
MattC

Reputation: 6344

No, setting the reference to null will not effect the thread, other than it has one less reference pointing at it. And yes, any object with active references pointing at it will not be garbage collected. If you want the thread to be eligible for GC (and more importantly stop doing stuff) then interrupt what it is doing:

someThread.interrupt();

from the Oracle docs:

An interrupt is an indication to a thread that it should stop what it is doing and do something else. It's up to the programmer to decide exactly how a thread responds to an interrupt, but it is very common for the thread to terminate

Upvotes: 2

Saurabh Gokhale
Saurabh Gokhale

Reputation: 46405

Live thread will continue running even its reference is set to null.
Just like any other object, when there are no references to it, it is eligible to GC. The tricky point is that a running thread has a reference in a ThreadGroup even if your program does not retain one, thus a running thread is never GCed.

Upvotes: 38

user207421
user207421

Reputation: 310957

what will happen to the thread?

Nothing.

Does it stop?

No.

Is it eligible for GC?

No.

Upvotes: 16

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