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If the else clause is provided and the condition is false, the code in the body of the if clause is ignored and the code in the body of the else clause is executed.
In all cases, control passes to the next statement following the if-else statement when the code in the if-else statement has finished executing. In other words, this is not a loop structure.
The switch-case statement is another implementation of the selection pillar mentioned earlier . The general syntax of a switch-case statement is shown in Figure 4 .
| Figure 4 . Syntax of a switch-case statement. |
|---|
switch(expression){
case constant://sequence of optional statements
break; //optionalcase constant:
//sequence of optional statementsbreak; //optional
..
.default //optional
//sequence of optional statements} |
The type of the expression
According to the book, Java Language Reference , by Mark Grand, the expression shown in the first line in Figure 4 must be of type byte , char , short , or int .
The behavior of the switch-case statement
The expression is tested against a series of case constants of the same type as the expression. If a matchis found, the sequence of optional statements associated with that case is executed.
Execution of statements continues until the optional break is encountered. When break is encountered, execution of the switch statement is terminated and control passes to the next statement followingthe switch statement.
If there is no break statement, all of the statements following the matching case will be executed including those in cases furtherdown the page.
The optional default keyword
If no match is found and the optional default keyword along with a sequence of optional statements has been provided, those statementswill be executed.
Labeled break
Java also supports labeled break statements. This capability can be used to cause Java to exhibit different behavior whenswitch statements are nested. This will be explained more fully in a later section on labeled break statements.
The for statement is another implementation of the loop pillar mentioned earlier .
Actions of a for loop
The operation of a loop normally involves three actions in addition to executing the code in the body of the loop:
Grouping the actions
Java provides the for loop construct that groups these three actions in one place.
The syntax of a for loop
A for loop consists of three clauses separated by semicolons as shown in Figure 5 .
| Figure 5 . Syntax of a for loop. |
|---|
for (first clause; second clause; third clause)
single or compound statement |
Contents of the clauses
The first and third clauses can contain one or more expressions, separated by the comma operator .
The comma operator
The comma operator guarantees that its left operand will be executed before its right operand.
(While the comma operator has other uses in C++, this is the only use of the comma operator in Java.)
Behavior and purpose of the first clause
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