If statement in Java

In current article we would like to show how to make choices in the code. There are many situations when a program branches out: if certain condition is true the program goes one way, otherwise it goes another. The choice may be more complicated, when there are more then two variants. If statement is the simplest tool to program choices in the code. To make explanation more illustrative, let's start with the example.

Example. Let us test if 4 is equal to 2 + 2.

Else way

In the example above you can see the program executing the first statement, because the condition is true. Putting false condition (2 + 2 == 3) in parentheses will make the program executing the second statement.

Double vs. single equals sign

Draw your attention to the fact that we are using double equals sign in condition. It denotes comparison, whereas single equals sing is an assignment operator. Fortunately Java won't compile the code, if you've put the single equals sign by mistake:

More than one statement

If "then" clause contains more than one statement, they must be placed in brackets:

Else branch is optional

Note, that in the recent example there is no else branch. It's not a mistake, using else branch is completely optional. It is possible that you don't need "then" branch or during the code's evolution it becomes unnecessary. You can use empty statement for "then" clause:

Although it is possible to use empty statement in "then" clause, such technique is considered as a bad programming style. To fix it use reversed condition instead:

The condition is interpreted as "if not 2 + 2 equals to 3".

Last remark

Note, that condition must be placed in parentheses. Failure to do so will result in compilation error:

Now, you mastered the last basic Java tool. It's time to get to practice.