With the basic built-in Java data types that you've seen in the previous chapters, each identifier corresponds to a single variable. But when you want to handle sets of values of the same type—the first 1,000 primes, for example—you really don't want to have to name them individually. What you need is an array.
Let's first get a rough idea of what an array is and how it works. An array is an object that is a named set of variables of the same type. Each variable in the array is called an array element. To reference a particular element in an array, you use the array name combined with an integer value of type int, called an index. You put the index between square brackets following the array name; for example, data refers to the element in the data array corresponding to the index value 99. The index for an array element is the offset of that particular element from the beginning of the array. The first element will have an index of 0, the second will have an index of 1, the third an index of 2, and so on. Thus, data refers to the hundredth element in the data array. The index value does not need to be an integer literal. It can be any expression that results in a value of type int that is equal to or greater than zero. Obviously a for loop is going to be very useful for processing array elements—which is one reason why you had to wait until now to hear about arrays.
4.1.1. Array Variables
An array variable and the array it refers to are separate entities. ...