Storing Information in Variables
You can put a value into a variable at the same time that you create the variable in a Java program. You also can put a value in the variable at any time later in the program.
To set up a starting value for a variable upon its creation, use the equal sign (=). The following is an example of creating a floating-point variable called pi with the starting value of 3.14:
float pi = 3.14;
All variables that store numbers can be set up in a similar fashion. If you're setting up a character or a string variable, quotation marks must be placed around the value as shown previously.
You also can set one variable equal to the value of another variable if they both are of the same type. Consider the following example:
int mileage = 300;
int totalMileage = mileage;
First, an integer variable called mileage is created with a starting value of 300. In the second line, an integer variable called totalMileage is created with the same value as mileage. Both variables will have the starting value of 300. In future hours, you will learn how to convert one variable's value to the type of another variable.
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If you do not give a variable a starting value, you must give it a value before you try to use it. If you don't, when you attempt to compile your program, the javac compiler will respond with an error message such as the following:
WarGame.java:7: Variable warships may not have been initialized.
warships = warships + 10;
^
1 error
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Another naming convention in Java is to capitalize the names of variables that will not change in value. These variables are called constants. The following creates three constants:
int TOUCHDOWN = 6;
int FIELDGOAL = 3;
int PAT = 1;
Because constants never change in value, you might wonder why one should ever be used—you can just use the value assigned to the constant instead. One of the advantages of using constants is that they can make a program easier to understand. For example, the variables Font.BOLD and Font.ITALIC are constants that hold integer values representing the style of the current font.
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