Variables were introduced in Chapter 1. Here, we will take a closer look at them. As you learned earlier, variables are declared using this form of statement,
where type is the data type of the variable, and var-name is its name. You can declare a variable of any valid type, including the simple types just described. When you create a variable, you are creating an instance of its type. Thus, the capabilities of a variable are determined by its type. For example, a variable of type boolean cannot be used to store floating-point values. Furthermore, the type of a variable cannot change during its lifetime. An int variable cannot turn into a char variable, for example.
All variables in Java must be declared ...