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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

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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.

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 10

  10 20 20

  20 20 10

  20 10 20

  Half-n-half Clue
 

3.

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")

  (D) & (E)

  (A), (C), (D) & (E)

  (A), (B) & (C)

  (C), (D) & (E)

  (A), (B), (C) & (D)

  Half-n-half Clue
 

4.

Which of the following statements are valid array declaration?
(A) int number();
(B) float average[];
(C) double[] marks;
(D) counter int[];

  (A) & (C)

  (B) & (C)

  (A)

  (D)

  Half-n-half Clue
 

5.

What will be the content of array variable table after executing the following code?
for(int i = 0; i < 3; i + +)
for(int j = 0; j < 3; j + +)
if(j = i) table[i][j] = 1;
else table[i][j] = 0;

  0 0 0
0 0 0
0 0 0

  0 0 1
0 1 0
1 0 0

  1 0 0
0 1 0
0 0 1

  1 0 0
1 1 0
1 1 1

  Half-n-half Clue
 

6.

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

  (B), (D) & (E)

  (A) & (E)

  (C) & (E)

  (E)

  Half-n-half Clue
 

7.

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

  java.lang.ThreadGroup

  java.lang.Object

  java.lang.Runnable

  java.lang.String

  java.lang.Thread

  Half-n-half Clue
 


 
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