innerclass question

[Mindy Hudson]

Can anyone help me with this.Which of the following statements is true? I think a,b,c,d are true.
a) An interface can contain a nested top-level inner class.
b) An interface can contain a member inner class.
c) A member inner class can implement an interface.
d) A static method can contain a local class.
e) A static method can contain a nested top-level class.

[Val Dra]

Can anyone help me with this.Which of the following statements is true? I think a,b,c,d are true.
a) An interface can contain a nested top-level inner class.
b) An interface can contain a member inner class.
c) A member inner class can implement an interface.
d) A static method can contain a local class.
e) A static method can contain a nested top-level class.
I don't know , but i think that interface can only contain a static class within it. C is true i think and D is true too don't know about A

[Mindy Hudson]

So A must be right and B is not?Can anyone please explain...

[Viral Thakkar]

Originally posted by Mindy Hudson:

Can anyone help me with this.Which of the following statements is true? I think a,b,c,d are true.
a) An interface can contain a nested top-level inner class.
b) An interface can contain a member inner class.
c) A member inner class can implement an interface.
d) A static method can contain a local class.
e) A static method can contain a nested top-level class.

Option A is right as Normally you can�t put any code inside an interface, but a static inner class can be part of an interface. Since the class is static it doesn�t violate the rules for interfaces � the static inner class is only placed inside the namespace of the interface:
interface IInterface {
static class Inner {
int i, j, k;
public Inner() {}
void f() {}
}
}
So Option B is wrong..
Option C is right as any class can implement the interface...
Option D is right as the class that is inside static method will become static local class......So that it can only access the static memnbers of enclosing class n object of local class can be created with out need of object of enclosing class.

Option E is wrong as nested top level classes cant be inside methods..

[Mindy Hudson]

Thank you Viral.You were of great help.

[Charlie Swanson]

I believe A, B, C, and D are correct. E is not correct.
Below is an example that runs for B.
public class test implements Timer1 {
public static void main(String args[]) {
test t1 = new test();
Timer1 timerVar = t1;
nested testNested = timerVar.new nested();
testNested.testMethod();
}
public void timerFired() {}
}
public interface Timer1
{
public abstract void timerFired();

class nested {
public void testMethod() {
System.out.println("test method"); }
}
}
Please explain any difference if you feel that b is correct.

[Jane Griscti]

Hi all,
A. True. All member classes in an interface are implicitly
static (JLS §9.5); a top-level nested class is a
static inner class
B. False. As all member classes are implicitly static (see A)
an interface cannot contain a non-static inner class
C. True. A member class can implement another
interface.

public interface TestInterface {
    class InnerA {}     // implicitly static
    
    // following compiles OK
    class InnerB implements InterfaceB {}
}
interface InterfaceB {}

D. True. ( see code below E )
E. False. Local classes can have no access modifier or be
declared final.

public class TestStatic {
    static void methodA () {
        class LocalClass {} ;       // compiles ok
        static class LocalClassA {} // compile error
    }
}

Hope that helps.

------------------
Jane Griscti
Sun Certified Java 2 Programmer
"When ideas fail, words come in very handy" -- Goethe

[Mindy Hudson]

Hi every one thaks for the answers.Will be posting more doubts.