You can write any statement under the if and else clauses. In fact, you could write another if statement under them. This is known as nesting. So, if you write an if statement inside another if statement, we call the arrangment as nested if statements.
The if statement written inside another if statement is called the inner if statement.
Similarly, the if statement which contains another if statement is called the outer if statement.
Nested if statements are very common in programming. When you nest if statements, you must always remember that the else clause is associated with the nearest if clause.
You can nest any number of if statements to any depth. We recommend you to keep it as simple as possible. Also, be sure to use indentation to indicate the structure of the nested statements.
Here is the general form of a nested if statement.
if (condition1)
if (condition2)
statement1
else
statement2
else
if (condition3)
statement3
else
statement4
Remember, you construct a nested if statement with regular if statements. So, you don’t have to use if statements under both the clauses if you don’t have to. Again, all the else clauses are optional.
Be careful when you use nested if statements, as it is easy to end up with statements that don’t work the way you expect them to. The key is knowing how Java pairs else clauses with if clauses. Each else clauses is matched with the nearest if clause that has not already been paired with an else clause.
Further, you cannot force Java to pair clauses using identation. Because indentation is white space that Java ignores.