Java For Dummies Quick Reference

if Statement

In its most basic form, an if statement executes a single statement or a block of statements if a boolean expression evaluates to true. Here’s the syntax:

if (boolean-expression)

statement

The boolean expression must be enclosed in parentheses. If you use only a single statement, it must end with a semicolon. However, the statement can also be a statement block enclosed by braces. In that case, each statement within the block needs a semicolon, but the block itself doesn’t.

Here’s an example:

double commissionRate = 0.0;

if (salesTotal > 10000.0)

commissionRate = 0.05;

In this example, a variable named commissionRate is initialized to 0.0 and then set to 0.05 if salesTotal is greater than 10000.0.

Here’s an example that uses a block rather than a single statement:

double commissionRate = 0.0;

if (salesTotal > 10000.0)

{

commissionRate = 0.05;

commission = salesTotal * commissionRate;

}

In this example, the two statements within the braces are executed if salesTotal is greater than $10,000. Otherwise, neither statement is executed.

An if statement can include an else clause that executes a statement or block if the boolean expression is not true. Its basic format is

if (boolean-expression)

statement

else

statement

Here’s an example:

double commissionRate;

if (salesTotal <= 10000.0)

commissionRate = 0.02;

else

commissionRate = 0.05;

In this example, the commission rate is set to 2% if the sales total is less than or equal to $10,000. If the sales total is greater ...