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 */
}