Java Reference
In-Depth Information
3.1
List six comparison operators.
Check
3.2
Show the printout of the following statements:
Point
System.out.println( 'a' < 'b' );
System.out.println( 'a' <= 'A' );
System.out.println( 'a' > 'b' );
System.out.println( 'a' >= 'A' );
System.out.println( 'a' == 'a' );
System.out.println( 'a' != 'b' );
3.3
Can the following conversions involving casting be allowed? If so, find the converted
result.
boolean b = true ;
i = ( int )b;
int i = 1 ;
boolean b = ( boolean )i;
3.3 if Statements
An if statement executes the statements if the condition is true.
Key
Point
The preceding program displays a message such as “
6
+
2
=
7
is false.” If you wish the
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, 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 statement
if (boolean-expression) {
statement(s);
}
The flowchart in Figure 3.1 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
diamond box is used to denote a Boolean condition and a rectangle box is for representing
statements.
If the boolean-expression evaluates to true , the statements in the block are executed.
As an example, see the following code:
flowchart
if (radius >= 0 ) {
area = radius * radius * PI;
System.out.println( "The area for the circle of radius " +
radius + " is " + area);
}
The flowchart of the preceding statement is shown in Figure 3.1b. If the value of radius
is greater than or equal to 0 , then the area is computed and the result is displayed; otherwise,
the two statements in the block will not be executed.
The boolean-expression is enclosed in parentheses. For example, the code in (a)
below is wrong. It should be corrected, as shown in (b).
 
 
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