long good-by ;  // bad identifier: "-" not allowed

short shrift = 0;  // OK

double bubble = 0, toil= 9, trouble = 8 // missing ";" at end.

byte the bullet ;    // bad identifier: can't contain a space

int  double;    // reserved word

char thisMustBeTooLong  ;   // OK in syntax, but a poor choice 
                            // for a variable name

int  8ball;    // can't start with a digit

Example Program

Here is another example program, containing several variable declarations.

class Example
{
  public static void main ( String[] args )
  {
    long   hoursWorked = 40;    
    double payRate = 10.0, taxRate = 0.10;    

    System.out.println("Hours Worked: " + hoursWorked );
    System.out.println("pay Amount  : " + (hoursWorked * payRate) );
    System.out.println("tax Amount  : " + (hoursWorked * payRate * taxRate) );
  }
}

The character * means multiply. In the program, (hoursWorked * payRate) means to multiply the number stored in hoursWorked by the number stored in payRate.

When it follows a character string, + means to add characters to the end of the character string. So  "Hours Worked: " + hoursWorked   makes a character string starting with "Hours Worked: " and ending with characters for the value of hoursWorked. The program will print out:

Hours Worked: 40
pay Amount  : 400.0
tax Amount  : 40.0

The program illustrates an

Important Idea: In a calculation or in printing, use the name of the variable to represent the value it holds.

For example, in the first System.out.println statement, the variable hoursWorked was used. This means "go get the value inside hoursWorked and use that value here".

Remember that if you want to see this program run, copy it from your Web browser, paste it into the window of Notepad, compile and run it. (See Chapter 7.)