Java Programming - Java.lang Class

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Exercise :: Java.lang Class - General Questions

1. 

What is the value of "d" after this line of code has been executed?

double d = Math.round ( 2.5 + Math.random() );

A. 2
B. 3
C. 4
D. 2.5

Answer: Option B

Explanation:

The Math.random() method returns a number greater than or equal to 0 and less than 1 . Since we can then be sure that the sum of that number and 2.5 will be greater than or equal to 2.5 and less than 3.5, we can be sure that Math.round() will round that number to 3. So Option B is the answer.


2. 

Which of the following would compile without error?

A. int a = Math.abs(-5);
B. int b = Math.abs(5.0);
C. int c = Math.abs(5.5F);
D. int d = Math.abs(5L);

Answer: Option A

Explanation:

The return value of the Math.abs() method is always the same as the type of the parameter passed into that method.

In the case of A, an integer is passed in and so the result is also an integer which is fine for assignment to "int a".

The values used in B, C & D respectively are a double, a float and a long. The compiler will complain about a possible loss of precision if we try to assign the results to an "int".


3. 

Which of the following are valid calls to Math.max?

  1. Math.max(1,4)
  2. Math.max(2.3, 5)
  3. Math.max(1, 3, 5, 7)
  4. Math.max(-1.5, -2.8f)

A. 1, 2 and 4
B. 2, 3 and 4
C. 1, 2 and 3
D. 3 and 4

Answer: Option A

Explanation:

(1), (2), and (4) are correct. The max() method is overloaded to take two arguments of type int, long, float, or double.

(3) is incorrect because the max() method only takes two arguments.


4. 

public class Myfile 
{ 
    public static void main (String[] args) 
    {
        String biz = args[1]; 
        String baz = args[2]; 
        String rip = args[3]; 
        System.out.println("Arg is " + rip); 
    } 
}
Select how you would start the program to cause it to print: Arg is 2

A. java Myfile 222
B. java Myfile 1 2 2 3 4
C. java Myfile 1 3 2 2
D. java Myfile 0 1 2 3

Answer: Option C

Explanation:

Arguments start at array element 0 so the fourth arguement must be 2 to produce the correct output.