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Inner Classes Online Exam Quiz

Important questions about Inner Classes. Inner Classes MCQ questions with answers. Inner Classes exam questions and answers for students and interviews.

1. Which statement, inserted at line 10, creates an instance of Bar ? class Foo { class Bar{ } } class Test { public static void main (String [] args) { Foo f = new Foo(); /* Line 10: Missing statement? */ } }

Options

A : Foo.Bar b = new Foo.Bar();

B : Foo.Bar b = f.new Bar();

C : Bar b = new f.Bar();

D : Bar b = f.new Bar();

2. Which constructs an anonymous inner class instance?

Options

A : Runnable r = new Runnable() { };

B : Runnable r = new Runnable(public void run() { });

C : Runnable r = new Runnable { public void run(){}};

D : System.out.println(new Runnable() {public void run() { }});

3. Which one create an anonymous inner class from within class Bar? class Boo { Boo(String s) { } Boo() { } } class Bar extends Boo { Bar() { } Bar(String s) {super(s);} void zoo() { // insert code here } }

Options

A : Boo f = new Boo(24) { };

B : Boo f = new Bar() { };

C : Bar f = new Boo(String s) { };

D : Boo f = new Boo.Bar(String s) { };

4. Which is true about an anonymous inner class?

Options

A : It can extend exactly one class and implement exactly one interface.

B : It can extend exactly one class and can implement multiple interfaces.

C : It can extend exactly one class or implement exactly one interface.

D : It can implement multiple interfaces regardless of whether it also extends a class.

5. Which is true about a method-local inner class?

Options

A : It must be marked final.

B : It can be marked abstract.

C : It can be marked public.

D : It can be marked static.

6. Which statement, if placed in a class other than MyOuter or MyInner , instantiates an instance of the nested class? public class MyOuter { public static class MyInner { public static void foo() { } } }

Options

A : MyOuter.MyInner m = new MyOuter.MyInner();

B : MyOuter.MyInner mi = new MyInner();

C : MyOuter m = new MyOuter(); MyOuter.MyInner mi = m.new MyOuter.MyInner();

D : MyInner mi = new MyOuter.MyInner();

7. Which statement is true about a static nested class?

Options

A : You must have a reference to an instance of the enclosing class in order to instantiate it.

B : It does not have access to nonstatic members of the enclosing class.

C : It's variables and methods must be static .

D : It must extend the enclosing class.

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