Bạn có thể thực hiện một danh sách theo nhiều cách. Cho một danh sách tuyến tính và rằng tất cả các yếu tố danh sách có cùng loại (trong trường hợp này, được xây dựng trong lớp Point), một mảng có vẻ như một sự lựa chọn tự nhiên. Bạn có thể khai báo kích thước của mảng thời gian biên dịch | LABORATORY 2 LABORATORY 2 Prelab Exercise Name__ Hour Period Section__ Date__ You can implement a list in many ways. Given that a list is linear and that all the list elements are of the same type in this case the built-in class Point an array seems a natural choice. You could declare the size of the array at compile-time as you did with the logbook array in Laboratory 1 but your Point List ADT will be more flexible if you specify the size of the array at runtime and dynamically allocate the memory required to store it. Memory allocation for the array is done by the constructor. The Point constructor is invoked during the execution of the program. Once called the PointList constructor allocates an array of points using Java s new operator. The statement below for example allocates memory for an array of maxsize points. The variable name ptlist is the reference through which we have access to this array of points. Point ptlist new Point maxsize During program execution a variable reference can become inaccessible. Whenever a point ptlist reference goes out of scope that is whenever the method containing the corresponding variable declaration terminates the ptlist variable is no longer accessible. In other words the program can no longer use the ptlist variable because it has gone out of scope. The memory allocated for ptlist may also become inaccessible through reassignment such as ptlist new Point 10 First assignment ptlist new Point 8 Reassignment first instance is inaccessible When all references to a memory location have been lost the memory location no longer serves any useful purpose and is called garbage. What happens to memory that was allocated for an instance variable such as the ptlist array when all references to that memory location have been lost Unlike object-oriented programming languages such as C where the programmer must explicitly manage memory deallocation Java has a .
