Lecture 8, Arrays West Virginia Univerity8讲，阵列西弗吉尼亚大学.docVIP

Chapter 9, Arrays The primitive and reference variables we have discussed so far are “single-valued” in that each contains a single value, either an exact value or a reference to an object. There is another category of variables that allows us to associate a single variable name with multiple values, these are called Arrays. In programs, arrays are used to store SETS of related values (called elements), that can be manipulated collectively or individually. Some of the things we might keep in arrays are: the students in a particular class, a set of numbers that need to be sorted or searched, or a set of points that need to be drawn on a graph. To create arrays, Java provides us with a “class” Array that permits the storage and retrieval of multiple values/objects of the same type, through access to a single variable name. The syntax to create an array in Java is : type [] identifier; int[] values; or type [] identifier = new type[i]; int[] values = new int[4]; In these examples: type represents the data type of the “elements” stored in the array. This “type” can be any primitive or reference (class) type identifier represents the variable name of the array variable being created. int [] intArray; creates an array of integers called intArray. At this point it is uninitialized which means that it has no storage associated with it, and thus it can not be used to store values. Before an array can be used, we must allocate storage, by indicating HOW many values will be stored in the array. We can do this by intArray = new int[4]; int[] anArray = new int[5]; creates an integer array called anArray and initializes it so that it can store a maximum of 5 values. Conceptually, when an array is allocated, a contiguous (sequential) set of bytes are allocated in memory to store the values contained in the array. In our previous example, this