Use the if statement to execute a statement
if a logical condition is true.
Use the optional else clause
to execute a statement if the condition is false.
An if statement looks as follows:
if (condition)
{ statement_1; }
else { statement_2; }
condition can be any expression
that evaluates to true or false.
See Boolean for an explanation
of what evaluates to true and false.
If condition evaluates to true, statement_1
is executed; otherwise, statement_2 is executed.
statement_1 and statement_2 can be any statement,
including further nested if statements.
You may also compound the statements
using else if to have
multiple conditions tested in sequence, as follows:
if (condition_1) {
statement_1;
} else if (condition_2) {
statement_2;
} else if (condition_n) {
statement_n;
}
else {
statement_last;
}
In the case of multiple conditions
only the first logical condition
which evaluates to true will be executed.
To execute multiple statements,
group them within a block statement ({ ... }) .
In general, it's good practice to always use block statements,
especially when nesting if statements:
if (condition) { statement_1_runs_if_condition_is_true;
statement_2_runs_if_condition_is_true; } else {
statement_3_runs_if_condition_is_false;
statement_4_runs_if_condition_is_false; }
It is advisable to not use simple assignments
in a conditional expression,
because the assignment can be confused
with equality when glancing over the code.
For example, do not use the following code:
if (x = y) { /* statements here */ }
If you need to use an assignment in a conditional expression,
a common practice is to put
additional parentheses around the assignment. For example:
if ((x = y)) { /* statements here */ }