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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.

Suppose that s1 and s2 are two strings. Which of the statements or expressions are valid?
(A) String s3 = s1 + s2;
(B) String s3 = s1 - s2;
(C) s1 <= s2
(D) s1.compareTo(s2);
(E) int m = s1.length();

  (A), (D) & (E)

  (D) & (E)

  (C), (D) & (E)

  (A), (C) & (E)

  (A), (B) & (C)

  Half-n-half Clue
 

2.

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.

  (C), (D) & (E)

  (D) & (E)

  (A), (B) & (D)

  (A), (B), (D) & (E)

  (B), (D) & (E)

  Half-n-half Clue
 

3.

The methods wait() and notify() are defined in

  java.lang.Object

  java.lang.Thread

  java.lang.ThreadGroup

  java.lang.Runnable

  java.lang.String

  Half-n-half Clue
 

4.

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)

  (B), (D) & (E)

  (E)

  (C) & (E)

  Half-n-half Clue
 

5.

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:

  Derived Derived Derived

  Base Base Derived

  Base Derived Derived

  Base Derived Base

  Half-n-half Clue
 

6.

Given the code
String s = new String("abc");
Which of the following calls are valid?
(A) s.trim()
(B) s.replace('a', 'A')
(C) s.substring(3)
(D) s.toUppercase()
(E) s.setCharAt(1,'A')
(F) s.append("xyz")

  (A), (B), (C) & (D)

  (D) & (E)

  (A), (B) & (C)

  (C), (D) & (E)

  (A), (C), (D) & (E)

  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

  10 20 10

  20 10 20

  20 20 10

  Half-n-half Clue
 


 
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