大任務：Java 重構

It's time for a little refactoring. Wikipedia says, "Refactoring or reorganizing code is the process of changing the internal structure of a program, without affecting its external behavior and with an aim to making it easier to understand.

2.1. Extract a subclass. 2.1.1. Add the Soldier class to the human package. 2.1.2. Get rid of the isSoldier field. 2.1.3. Move the necessary methods from Human to Soldier. 2.1.4. Update the Human constructor's signature. 2.2. Pull up the body of the constructor.

3.1. Push down a field. Push down the course field to the appropriate class. Make it private. 3.2. Push down a method. Push down the getter for the course field to the appropriate class. 3.3. Extract an interface. 3.3.1. Create an Alive interface in the human package.

4.1. Replace inheritance with delegation. 4.1.1. The University class must not inherit Student. 4.1.2. The University class must have a students list. Don't forget to initialize it. 4.1.3. Add a setter and getter for students.

5.1. Create a template method. 5.1.1. Add a String getPosition() method to the Human class. It should return the string "Person". 5.1.2. Override this method in the Student and Teacher classes. The method should return "Student" and "Teacher", respectively.

6.1. Replace a parameter with a set of specialized methods. Replace the Student class's setValue() method with specialized setCourse() and setAverageGrade() methods. 6.2. Add a parameter. Add a double parameter to the getStudentWithAverageGrade() method so the average grade of the required student.

7.1. Parameterize a method. Replace the incAverageGradeBy01() and incAverageGradeBy02() methods with an incAverageGrade(double delta) method. 7.2. Pass an entire object. Rewrite the addStudentInfo() method so that it takes a Student object as an argument.

8.1. Remove a setter. Remove the setId() method. The id field should be set only when the object is created. 8.2. Hide a method (field). Change the visibility of the nextId field to match the area where it is used.

9.1. Self-encapsulate a field. Rewrite the incAverageGrade() method, using a setter and getter to access averageGrade. 9.2. Replace an array field with an object. Replace the int[] size array with an instance of a new Size type, containing the following public fields: int height and int weight.

Understand the code in the car package. 10.1. Replace a constructor with a factory method. 10.1.1. Declare Truck, Sedan, and Cabriolet classes that inherit Car. 10.1.2. Add constructors that have an int numberOfPassengers constructors.

11.1. Replace an error code with an exception. Rewrite the fill(double numberOfGallons) method to throw an Exception if there is an error. 11.2. Decompose a conditional expression. 11.2.1. Add and implement a method in the Car class that determines whether the passed date belongs to summer.

12.1. Combine conditional expressions. 12.1.1. In the Car class, add a private method that indicates whether passengers can be carried: boolean canPassengersBeCarried(). The method should return true if the driver is available (isDriverAvailable) and there is fuel.

Understand the code in the user package. 13.1. Extract a method. Add a printInfo() method that displays the first and last name on the console, formatted as follows - First name: Jason; Last name: Slater. Replace the duplicate code in printUsers() with a method call.

14.1. Move a field. Replace the isAnnaMale and isRomanMale fields with a male field in the appropriate class. Add a setter and getter for the new field (when choosing method names, consider the field type). 14.2. Extract a class. 14.2.1. Add an Address class to the user package.

Great. You've mastered basic refactoring techniques: Pull up a field, pull up a method, Encapsulate a collection, extract a subclass, pull up the body of a constructor, push down a method, push down a field, extract an interface, collapse a hierarchy, replace inheritance with delegation.