SCJP - 12 - Given Example

Answer:

B is correct, an abstract class need not implement any or all of an interface’s methods.
E is correct, the class implements the interface method and additionally overloads the
twiddle() method.
A is incorrect because abstract methods have no body.
C is incorrect because classes implement interfaces they don’t extend them.
D is incorrect because overloading a method is not implementing it.
(Objective 5.4)
===

public abstract interface Frobnicate { public void twiddle(String s); }
// Which is a correct class? (Choose all that apply.)
A. public abstract class Frob implements Frobnicate {
public abstract void twiddle(String s) { }
}
B. public abstract class Frob implements Frobnicate { }
C. public class Frob extends Frobnicate {
public void twiddle(Integer i) { }
}
D. public class Frob implements Frobnicate {
public void twiddle(Integer i) { }
}
E. public class Frob implements Frobnicate {
public void twiddle(String i) { }
public void twiddle(Integer s) { }
}