Explanation to a certain java command

Question

System.out.println(((Window)this).size);

Say we have a class Window and the above command is written inside a method in a subclass. I want some help understanding what (Window)this does exactly. Where it refers to.

score 3 · Accepted Answer · answered Mar 15 '15 at 20:36

3

Suppose both the sub-class and the Window class have a member called class. In this case, the sub-class's size hides Window's size.

((Window)this).size returns the size member of the Window class (assuming it's accssible), while this.size will return the size member of the sub-class.

answered Mar 15 '15 at 20:36

Eran

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So if we say that Window is the superclass writing ((Window)this).size and super.size is the same thing? – JimS Mar 15 '15 at 20:39
@ohyez96 Yes, both would return the same value – Eran Mar 15 '15 at 20:45

score 0 · Answer 2 · edited May 23 '17 at 11:50

System.out.println(((Window)this).size);

Can be broken down in steps as:

this A reference to the current instance
(Window)this cast as the Window class so non private Window members are accessible
(Window)this.size Access the size member of this Window
System.out refers to the reference variable of the type PrintStream class
System Statically refers to a final class from java.lang package
out a reference to the PrintStream class and a static member of System class
println is a method of PrintStream class

Altogether,

System.out.println(((Window)this).size);

will send this windows size to the console (provided out hasn't been redirected) and follow it with a new line.

Explanation to a certain java command

2 Answers2