7.2 Ap0020: self-assessment, assignment and arithmetic operators  (Page 6/11)

Answers

Answer 15

C. -3 2

Explanation 15

String concatenation

This program uses String concatenation, which has not been previously discussed in this group of self-assessment modules.

In this case, the program executes both an integer divide operation and an integer modulus operation, using String concatenation to display both results on a single line of output.

Quotient = -3 with a remainder of 2

Thus, the displayed result is the integer quotient followed by the remainder.

What is String concatenation?

If either operand of the plus (+) operator is of type String , no attempt is made to perform arithmetic addition. Rather, the other operand isconverted to a String , and the two strings are concatenated.

A space character, " "

The string containing a space character (" ") in this expression appears as the right operand of one plus operator and as the left operand of the other plusoperator.

If you already knew about String concatenation, you should have been able to figure out the correct answer to the question on the basis of the answers toearlier questions in this module.

Back to Question 15

Answer 14

D. NaN

Explanation 14

Floating modulus operation involves floating divide

The modulus operation with floating operands and 0.0 as the right operand produces NaN , which stands for Not a Number .

What is the actual value of Not a Number?

A symbolic constant that is accessible as Double.NaN specifies the value that is returned in this case.

Be careful what you try to do with it. It has some peculiar behavior ofits own.

Back to Question 14

Answer 13

D. 1.5499999999999996

Explanation 13

A totally incorrect result

Unfortunately, due to floating arithmetic inaccuracy, the modulus operation in this program produces an entirely incorrect result.

The result should be 0.0, and that is the result produced by my hand calculator.

Terminates one step too early

However, this program terminates the repetitive subtraction process one step too early and produces an incorrect remainder.

Be careful

This program is included here to emphasize the need to be very careful how you interpret the result of performing modulus operations on floating operands.