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Inner Classes

Q: 01 Given:

10. class Line { 
11. public static class Point {} 
12. } 
13. 
14. class Triangle { 
15. // insert code here 
16. }
Which code, inserted at line 15, creates an instance of the Point class defined in Line ?
  1. Point p = new Point();
  2. Line.Point p = new Line.Point();
  3. The Point class cannot be instatiated at line 15.
  4. Line l = new Line() ; l.Point p = new l.Point();
Answer: B

Q: 02 Given:

11. static class A { 
12. void process() throws Exception { throw new Exception(); } 
13. } 
14. static class B extends A { 
15. void process() { System.out.println("B "); } 
16. } 
17. public static void main(String[] args) { 
18. A a = new B(); 
19. a.process(); 
20. }
What is the result ?
  1. B
  2. The code runs with no output.
  3. An exception is thrown at runtime
  4. Compilation fails because of an error in line 15.
  5. Compilation fails because of an error in line 18.
  6. Compilation fails because of an error in line 19.
Answer: F

Q: 03 Given:

 
1. package geometry; 
2. public class Hypotenuse { 
3. public InnerTriangle it = new InnerTriangle(); 
4. class InnerTriangle { 
5. public int base; 
6. public int height; 
7. } 
8. }
Which statement is true about the class of an object that can reference the variable base ?
  1. It can be any class.
  2. No class has access to base.
  3. The class must belong to the geometry package.
  4. The class must be a subclass of the class Hypotenuse.
Answer: C

Q: 04 Given:

10. class Line { 
11. public class Point { public int x,y;} 
12. public Point getPoint() { return new Point(); } 
13. } 
14. class Triangle { 
15. public Triangle() { 
16. // insert code here 
17. } 
18. }
Which code, inserted at line 16, correctly retrieves a local instance of a Point object ?
  1. Point p = Line.getPoint();
  2. Line.Point p = Line.getPoint();
  3. Point p = (new Line()).getPoint();
  4. Line.Point p = (new Line()).getPoint();
Answer: D

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