Declarations and Access Control problems
- 1. Which of the following class level (nonlocal) variable declarations will not compile?
Options- A. protected int a;
- B. transient int b = 3;
- C. private synchronized int e;
- D. volatile int d; Discuss
Correct Answer: private synchronized int e;
Explanation:
Option A and B will compile because protected and transient are legal variable modifiers. Option D will compile because volatile is a proper variable modifier.
- 2. Given a method in a protected class, what access modifier do you use to restrict access to that method to only the other members of the same class?
Options- A. final
- B. static
- C. private
- D. protected
- E. volatile Discuss
Correct Answer: private
Explanation:
Option A, B, D, and E are wrong because protected are the wrong access modifiers, and final, static, and volatile are modifiers but not access modifiers.
- 3. Which is a valid declaration within an interface?
Options- A. public static short stop = 23;
- B. protected short stop = 23;
- C. transient short stop = 23;
- D. final void madness(short stop); Discuss
Correct Answer: public static short stop = 23;
Explanation:
(B) and (C) are incorrect because interface variables cannot be either protected or transient. (D) is incorrect because interface methods cannot be final or static.
- 4. Which of the following code fragments inserted, will allow to compile?
public class Outer { public void someOuterMethod() { //Line 5 } public class Inner { } public static void main(String[] argv) { Outer ot = new Outer(); //Line 10 } }
Options- A. new Inner(); //At line 5
- B. new Inner(); //At line 10
- C. new ot.Inner(); //At line 10
- D. new Outer.Inner(); //At line 10 Discuss
Correct Answer: new Inner(); //At line 5
Explanation:
Option A compiles without problem.
Option B gives error - non-static variable cannot be referenced from a static context.
Option C package ot does not exist.
Option D gives error - non-static variable cannot be referenced from a static context.
- 5. Which is valid in a class that extends class A?
class A { protected int method1(int a, int b) { return 0; } }
Options- A. public int method1(int a, int b) {return 0; }
- B. private int method1(int a, int b) { return 0; }
- C. public short method1(int a, int b) { return 0; }
- D. static protected int method1(int a, int b) { return 0; } Discuss
Correct Answer: public int method1(int a, int b) {return 0; }
Explanation:
Option A is correct - because the class that extends A is just simply overriding method1.
Option B is wrong - because it can't override as there are less access privileges in the subclass method1.
Option C is wrong - because to override it, the return type needs to be an integer. The different return type means that the method is not overriding but the same argument list means that the method is not overloading. Conflict - compile time error.
Option D is wrong - because you can't override a method and make it a class method i.e. using static.
- 6. What is the most restrictive access modifier that will allow members of one class to have access to members of another class in the same package?
Options- A. public
- B. abstract
- C. protected
- D. synchronized
- E. default access Discuss
Correct Answer: default access
Explanation:
Option A and C are wrong because public and protected are less restrictive. Option B and D are wrong because abstract and synchronized are not access modifiers.
- 7. Which of the following is/are legal method declarations?
- protected abstract void m1();
- static final void m1(){}
- synchronized public final void m1() {}
- private native void m1();
Options- A. 1 and 3
- B. 2 and 4
- C. 1 only
- D. All of them are legal declarations. Discuss
Correct Answer: All of them are legal declarations.
Explanation:
- 8. Which two of the following are legal declarations for nonnested classes and interfaces?
- final abstract class Test {}
- public static interface Test {}
- final public class Test {}
- protected abstract class Test {}
- protected interface Test {}
- abstract public class Test {}
Options- A. 1 and 4
- B. 2 and 5
- C. 3 and 6
- D. 4 and 6 Discuss
Correct Answer: 3 and 6
Explanation:
(1) is wrong because a class cannot be abstract and final?there would be no way to use such a class. (2) is wrong because interfaces and classes cannot be marked as static. (4) and (5) are wrong because classes and interfaces cannot be marked as protected.
- 9. Which three are valid method signatures in an interface?
- private int getArea();
- public float getVol(float x);
- public void main(String [] args);
- public static void main(String [] args);
- boolean setFlag(Boolean [] test);
Options- A. 1 and 2
- B. 2, 3 and 5
- C. 3, 4, and 5
- D. 2 and 4 Discuss
Correct Answer: 2, 3 and 5
Explanation:
(1), is incorrect because an interface method must be public; if it is not explicitly declared public it will be made public implicitly. (4) is incorrect because interface methods cannot be static.
- 10. Which three form part of correct array declarations?
- public int a [ ]
- static int [ ] a
- public [ ] int a
- private int a [3]
- private int [3] a [ ]
- public final int [ ] a
Options- A. 1, 3, 4
- B. 2, 4, 5
- C. 1, 2, 6
- D. 2, 5, 6 Discuss
Correct Answer: 1, 2, 6
Explanation:
Option (3) is not a correct array declaration. The compiler complains with: illegal start of type. The brackets are in the wrong place. The following would work: public int[ ] a
Option (4) is not a correct array declaration. The compiler complains with: ']' expected. A closing bracket is expected in place of the 3. The following works: private int a []
Option (5) is not a correct array declaration. The compiler complains with 2 errors:
']' expected. A closing bracket is expected in place of the 3 and
<identifier> expected A variable name is expected after a[ ] .
Programming
Copyright ©CuriousTab. All rights reserved.