Varieties of if Statements

You should not write a program that depends on a true or false result with a floating point == operation.

There are many ways to use the if statement. The statement can be used with one or two branches, and a branch can include one or more statements. The table that shows these variations.

The booleanExpression in each of these varieties evaluates to true or false. Boolean expressions come in a variety of forms, which allow you to carefully state the conditions under which each branch will execute (see the next chapter for this).

 
if ( booleanExpression )
  statement;

if ( booleanExpression )
{
  one or more statements
}

if ( booleanExpression )
  statement;
else 
  statement;

if ( booleanExpression )
{
  one or more statements
}
else 
{
  one or more statements
}

if ( booleanExpression )
  statement;
else 
{
  one or more statements
}

if ( booleanExpression )
{
  one or more statements
}
else 
  statement;

The style of indenting used in the above leads to fewer errors than other styles you may have seen. An experiment with a group of professional programmers found this to be true. Of course, the Java compiler ignores indenting and blank lines. Use this style unless there is a good reason not to (such as an employer or instructor that requires a different style).

No matter which style you use, be consistent. Use the same number of spaces for indenting. (I use two spaces. Many people prefer four.) Soon you will be able to visuallize the logic of your programs. Programming and error catching will be easier.