案例简介
通过一个简单的案例具体的实现一下封装。
通过java语言和面向对象的思想，模拟一个场景的实现。
案例: 学校开设了计算机科学与应用这个专业,专业编号: J0001;学制年限: 4年;
现在有三个学生报名了该学校。
实现的效果图:
package cn.mtianyan.computer;public class Subject { public Subject(String name, String code, int year){ this.setName(name); this.setCode(code); this.setYear(year);
} public void showInfo(){
System.out.println("专业信息如下:");
System.out.println("专业名称: " + this.name);
System.out.println("专业编号: " + this.code);
System.out.println("学制年限: " + this.year +"年");
System.out.println("=====================");
} private String name; public String getName() { return name;
} public void setName(String name) { this.name = name;
} public String getCode() { return code;
} public void setCode(String code) { this.code = code;
} public int getYear() { return year;
} public void setYear(int year) { this.year = year;
} private String code; private int year;
}package cn.mtianyan.computer;public class Student { public Student(String name,String studentID, String sex,int age,Subject subject){ this.setName(name); this.setStudentID(studentID); this.setAge(age); this.setSex(sex); this.subject = subject;
} public void showInfo(){
System.out.println("==================");
System.out.println("姓名: "+name);
System.out.println("学号: "+studentID);
System.out.println("性别: "+sex);
System.out.println("年龄: "+age);
System.out.println("所报专业名称: "+ subject.getName());
System.out.println("学制年限: "+ subject.getYear());
} private String name; public String getName() { return name;
} public void setName(String name) { this.name = name;
} public String getStudentID() { return studentID;
} public void setStudentID(String studentID) { this.studentID = studentID;
} public String getSex() { return sex;
} public void setSex(String sex) { this.sex = sex;
} public int getAge() { return age;
} public void setAge(int age) { this.age = age;
} private String studentID; private String sex; private int age; private Subject subject;
}package cn.mtianyan.computer;public class Test { public static void main(String[] args) {
Subject subject = new Subject("计算机科学与应用","J0001",4);
subject.showInfo();
Student student1 = new Student("张三","S01","男",18, subject);
student1.showInfo();
Student student2 = new Student("李四","S02","女",17, subject);
student2.showInfo();
Student student3 = new Student("王五","S03","男",18, subject);
student3.showInfo();
}
}运行结果:
上面是我个人的实现.
综合案例
计算机科学与应用是一个对象。 三个学生是三个对象。学科专业类 & 专业类
类:
专业: 专业名称、编号、学制年限
学生: 姓名、学号、性别、年龄
编写Subject类
啊啊啊，英语真季二茶，Get到了。Subject是学科。
分包存储: cn.mtianyan.model cn.mtianyan.test
package cn.mtianyan.model;/**
* 专业类
* @author mtianyan
*/public class Subject { // 成员属性：学科名称、学科编号、学制年限、报名选修的学生信息、报名选修的学生个数
private String subjectName; private String subjectNo; private int subjectLife; private Student[] myStudents; // 专业学生数组
private int studentNum;
// 无参构造方法
public Subject() {
} // 带参构造，带参构造，实现对全部属性的赋值
public Subject(String subjectName, String subjectNo, int subjectLife) { // this.subjectName=subjectName;
this.setSubjectName(subjectName); this.setSubjectNo(subjectNo); this.setSubjectLife(subjectLife);
}
public void setSubjectName(String subjectName) { this.subjectName = subjectName;
} public String getSubjectName() { return this.subjectName;
} public String getSubjectNo() { return subjectNo;
} public void setSubjectNo(String subjectNo) { this.subjectNo = subjectNo;
} public int getSubjectLife() { return subjectLife;
} // 设置学制年限，限制必须>0
public void setSubjectLife(int subjectLife) { if (subjectLife <= 0) return; this.subjectLife = subjectLife;
} /**
* 获取选修专业的学生信息 如果保存学生信息的数组未被初始化，则，先初始化长度200
* @return 保存学生信息的数组
*/
public Student[] getMyStudents() { if(this.myStudents==null) this.myStudents=new Student[200]; return myStudents;
} public void setMyStudents(Student[] myStudents) { this.myStudents = myStudents;
} public int getStudentNum() { return studentNum;
} public void setStudentNum(int studentNum) { this.studentNum = studentNum;
} /**
* 专业介绍的方法
* @return 专业介绍的相关信息，包括名称、编号、年限
*/
public String info() {
String str = "专业信息如下：\n专业名称：" + this.getSubjectName() + "\n专业编号：" + this.getSubjectNo() + "\n学制年限："
+ this.getSubjectLife() + "年"; return str;
}
public void addStudent(Student stu){ /*
* 1、将学生保存到数组中
* 2、将学生个数保存到studentNum
* */
//1、将学生保存到数组中
for(int i=0;i<this.getMyStudents().length;i++){ if(this.getMyStudents()[i]==null){
stu.setStudentSubject(this); this.getMyStudents()[i]=stu; //2、将学生个数保存到studentNum
this.studentNum=i+1; return;
}
}
}
}这里我们的info方法在设计的时候返回String而不是直接在方法内打印，体现了单一职责原则，这样的设计使得这些字符串如果后期不是在控制台打印，而是做其他处理更方便。
编写Student类
package cn.mtianyan.model;public class Student { // 成员属性：学号、姓名、性别、年龄、专业
private String studentNo; private String studentName; private String studentSex; private int studentAge; private Subject studentSubject;
// 无参构造方法
public Student() {
} //多参构造方法，实现对学号、姓名、性别、年龄的赋值
public Student(String studentNo, String studentName, String studentSex, int studentAge) { this.setStudentNo(studentNo); this.setStudentName(studentName); this.setStudentSex(studentSex); this.setStudentAge(studentAge);
} // 多参构造方法，实现对全部属性的赋值
public Student(String studentNo, String studentName, String studentSex, int studentAge,Subject studentSubject) { this.setStudentNo(studentNo); this.setStudentName(studentName); this.setStudentSex(studentSex); this.setStudentAge(studentAge); // this.studentAge=studentAge;
this.setStudentSubject(studentSubject);
} public String getStudentNo() { return studentNo;
} public void setStudentNo(String studentNo) { this.studentNo = studentNo;
} public String getStudentName() { return studentName;
} public void setStudentName(String studentName) { this.studentName = studentName;
} public String getStudentSex() { return studentSex;
} public void setStudentSex(String studentSex) { // 限制性别只能是“男”或者“女”，反之，强制赋值为“男”
if(studentSex.equals("男") | studentSex.equals("女")){ this.studentSex = studentSex;
}else { this.studentSex = "男";
}
} public int getStudentAge() { return studentAge;
} /**
* 给年龄赋值，限定必须在10--100之间，反之赋值为18
*
* @param studentAge
* 传入的年龄
*/
public void setStudentAge(int studentAge) { if (studentAge < 10 || studentAge > 100) this.studentAge = 18; else
this.studentAge = studentAge;
} /**
* 获取专业对象，如果没有实例化，先实例化后再返回
* @return 专业对象信息
*/
public Subject getStudentSubject() { if(this.studentSubject==null) this.studentSubject=new Subject(); return studentSubject;
} public void setStudentSubject(Subject studentSubject) { this.studentSubject = studentSubject;
} /**
* 学生自我介绍的方法
*
* @return 自我介绍的信息，包括姓名、学号、性别、年龄
*/
public String introduction() {
String str = "学生信息如下：\n姓名：" + this.getStudentName() + "\n学号：" + this.getStudentNo() + "\n性别："
+ this.getStudentSex() + "\n年龄：" + this.getStudentAge()+ "\n所报专业名称：" + this.getStudentSubject().getSubjectName() + "\n学制年限："
+ this.getStudentSubject().getSubjectLife(); return str;
} /**
* 学生自我介绍的方法
* @param subjectName 所学专业名称
* @param subjectLife 学制年限
* @return 自我介绍的信息，包括姓名、学号、性别、年龄、所学专业名称、学制年限
*/
public String introduction(String subjectName, int subjectLife) {
String str = "学生信息如下：\n姓名：" + this.getStudentName() + "\n学号：" + this.getStudentNo() + "\n性别："
+ this.getStudentSex() + "\n年龄：" + this.getStudentAge() + "\n所报专业名称：" + subjectName + "\n学制年限："
+ subjectLife; return str;
} /**
* 学生自我介绍的方法
* @param mySubject 所选专业的对象
* @return自我介绍的信息，包括姓名、学号、性别、年龄、所学专业名称、学制年限
*/
public String introduction(Subject mySubject){
String str = "学生信息如下：\n姓名：" + this.getStudentName() + "\n学号：" + this.getStudentNo() + "\n性别："
+ this.getStudentSex() + "\n年龄：" + this.getStudentAge() + "\n所报专业名称：" + mySubject.getSubjectName() + "\n学制年限："
+ mySubject.getSubjectLife()+"\n专业编号："+mySubject.getSubjectNo(); return str;
}
}
作者：天涯明月笙
链接：https://www.jianshu.com/p/8610f0818a99
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