SELECTIONS - Introduction to Java Programming: Comprehensive Version - page 78

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3.1

List six relational operators.

Check

3.2

Point

Assuming that x is 1 , show the result of the following Boolean expressions:
(x > 0 )
(x < 0 )
(x != 0 )
(x >= 0 )
(x != 1 )

3.3

Can the following conversions involving casting be allowed? Write a test program to
verify your answer.
boolean b = true ;
i = ( int )b;

int i = 1 ;
boolean b = ( boolean )i;

3.3 if Statements
An if statement is a construct that enables a program to specify alternative paths of execution.

Key
Point

The preceding program displays a message such as “6 7 is false.” If you wish the

+ 2 =

message to be “6 + 2 = 7 is incorrect,” you have to use a selection statement to make this

minor change.
Java has several types of selection statements: one-way if statements, two-way if-else
statements, nested if statements, multi-way if-else statements, switch statements, and
conditional expressions.
A one-way if statement executes an action if and only if the condition is true . The syntax
for a one-way if statement is:

why if statement?

if (boolean-expression) {
statement(s);
}

if statement

The flowchart in Figure 3.1a illustrates how Java executes the syntax of an if statement.
A flowchart is a diagram that describes an algorithm or process, showing the steps as boxes
of various kinds, and their order by connecting these with arrows. Process operations are
represented in these boxes, and arrows connecting them represent the flow of control. A dia-
mond box denotes a Boolean condition and a rectangle box represents statements.

flowchart

false false

boolean-
expression

(radius >= 0)

true

true

area = radius * radius * PI;
System.out.println("The area for the circle of" +
" radius " + radius + " is " + area);

Statement(s)

(a) (b)

F IGURE 3.1

An if statement executes statements if the boolean-expression evaluates to true .