Why does invokeLater execute in the main thread?

Question

I just encountered this "bug", but I'm not sure if this is intended: Code:

public static Object someMethod(){     assert SwingUtilities.isEventDispatchThread();     return new Object(); }  public static void main(String[] args){     SwingUtilities.invokeLater(() -> someMethod().toString());//First Example     SwingUtilities.invokeLater(someMethod()::toString);//Second Example } 

In the first example someMethod is being executed on the swing Thread, but in the second example it is not, although it should be in my opinion.

Is this a bug or is this intended?

Answer 1

To me it seems like a misunderstanding on your side

The first line is like saying: "Ok, Swing, what I want you to invokeLater is someMethod().toString()". So Swing executes it

The second line is like saying: "Ok, Swing, what I want you to invokeLater is the method toString() of the object returned by the method someMethod()". A someMethod() method that I am executing right now

So the result is completely logical to me

Just keep in mind that before evaluating a function (in this case invokeLater) Java needs to evaluate all arguments. So in the first case Java evaluate a lambda function (no need to execute it) and in the second case it encounters a method invocation so it needs to execute it