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Java Programming : Arrays and java.lang.* : Multiple Choice


Questions about arrays and classes in the java.lang package.

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Multiple choice

Your Performance  

1.

Which of the following statements are true?
(A) A Java monitor must either extend Thread or implement Runnable.
(B) The sleep() method should be enclosed in try ... catch block.
(C) The yield() method should be enclosed in try ... catch block.
(D) A thread can be temporarily suspended from running by using the wait() method.
(E) A suspended thread using suspend() method can be revived using the resume() method.

  (B), (D) & (E)

  (A), (B), (D) & (E)

  (D) & (E)

  (A), (B) & (D)

  (C), (D) & (E)

  Half-n-half Clue
 

2.

Which of the following methods belong to the String class?

  substring()

  None of these

  equals()

  compareTo()

  All of these

  length()

  Half-n-half Clue
 

3.

Which of the following are the wrapper classes?
(A) Random
(B) Byte
(C) Vector
(D) Integer
(E) Short
(F) Double
(G) String

  (D), (E) & (F)

  (B), (D), (E) & (F)

  (B), (D) & (F)

  (A), (B), (D), (E) & (F)

  (B), (D) & (E)

  Half-n-half Clue
 

4.

Given the class definitions
class Base
{
void display ()
{ System.out.println("Base"); }
}
class Derived extends Base
{
void display ()
{ System.out.println("Derived"); }
}
and objects
Base b = new Base();
Derived d = new Derived();
Base bd = new Derived;

then the print statements
System.out.print(b.display() + " ");
System.out.print(d.display() + " ");
System.out.print(bd.display() + " ");
System.out.println();
will display:

  Base Derived Base

  Base Derived Derived

  Derived Derived Derived

  Base Base Derived

  Half-n-half Clue
 

5.

Consider the following code
int number[] = new int[5]; After execution of this statement, which of the following are true?
(A) number[0] is undefined
(B) number[5] is undefined
(C) number[4] is null
(D) number[2] is 0
(E) number.length() is 5

  (A) & (E)

  (E)

  (B), (D) & (E)

  (C) & (E)

  Half-n-half Clue
 

6.

When we implement the Runnable interface, we must define the method

  init()

  resume()

  start()

  main()

  run()

  Half-n-half Clue
 

7.

Given the following code:
class Base { int x = 10; }
class Derived extends Base
{ int x = 20; }

Base b = new Base();
Derived d = new Derived ( );
Base bd = new Derived();
The statement
System.out.println(b.x + " " + d.x + " " + bd.x);
will produce the output

  10 20 20

  20 20 10

  10 20 10

  20 10 20

  Half-n-half Clue
 


 
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