CONTROL STRUCTURES I: SELECTION - Java Programming: From Problem Analysis to Program Design - page 192

Sample Run: Figure 4-3 shows a sample run of this program.

FIGURE 4-3 Sample run of Example 4-7

The statement in Line 1 displays the input dialog box and prompts the user to enter an
integer. The entered number is stored as a string in numString . The statement in Line 2
uses the method parseInt of the class Integer , converts the value of numString
into the number, and stores the number in the variable number . The statement in Line 3
copies the value of number into temp . The statement in Line 4 checks whether number is
negative. If number is negative, the statement in Line 5 changes number to a positive
number. The statement in Line 6 displays the message dialog box and shows the original
number, stored in temp , and the absolute value of the number stored in number .

EXAMPLE 4-8

Consider the following statement:

if score >= 90
grade = 'A';
This statement illustrates an incorrect version of an if statement. The parentheses around
the logical expression are missing, which is a syntax error.

Putting a semicolon after the parentheses following the logical expression in an if statement
(that is, before the statement) is a semantic error. If the semicolon immediately follows the
closing parenthesis, the if statement will operate on the empty statement.

EXAMPLE 4-9

Consider the following Java statements:

if (score >= 90); //Line 1

grade = 'A'; //Line 2