Instantiate an Inner class from within a static method of its enclosing Class [duplicate]

Question

we know that Static contexts can't reference any instance of any type, but what happens with main method, how the following code sample compiles with no problem:

public class MyOuter
{
    public static void main(String[] args) 
    {
        MyOuter mo = new MyOuter(); // gotta get an instance!
        MyOuter.MyInner inner = mo.new MyInner();
        inner.seeOuter();

        //Or

        MyOuter.MyInner inner = new MyOuter().new MyInner();
    } 

    class MyInner
    {
        public void seeOuter(){}
    }
 }

isn't it forbidden to instantiate an inner class from within a static context in it's enclosing class?

Jon Skeet · Accepted Answer · 2012-09-18 09:05:32Z

5

isn't it forbidden to instantiate an inner class from within a static context in it's enclosing class?

No - it's forbidden to instantiate an inner class without an instance of the enclosing class. In your case, you do have an instance of the enclosing class:

new MyOuter().new MyInner();

That's entirely fine.

The only reason you can normally get away without specifying the enclosing class from an instance method is that it's equivalent to

// Within an instance method
this.new MyInner();

See section 15.9.2 of the JLS for more details. Your constructor call is a "qualified class instance creation expression".

answered Sep 18, 2012 at 9:05

Jon Skeet

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