Java封装案例

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在类的getter/setter方法中在getter方法中要先实列话

在构造方法中无参构造（必须要构造）好处很多！！！

描述学生信息及相关联的专业信息

把Subject和Stydent的属性进行连接有3中方法

Student中的代码

Subject类中的代码

test类中的代码及输出

专业信息如下:
专业名称   计算机科学
专业编号    J0001
学制年限     4
==============================
学生信息如下:
我的名字是张三
我的学号为 S01
性别为性别错误
年龄为 18
所在学科为计算机科学
学科的年制 4
==============================
学生信息如下:
我的名字是李四
我的学号为 S02
性别为女
年龄为 20
所在学科为计算机科学学院
学科的年制 4
==============================
学生信息如下:
我的名字是王五
我的学号为 S03
性别为男
年龄为 21
所在学科为计算机科学
学科的年制 4

新增需求：计算机专业有多少人

完整代码如下

subject类

package com.jiedada.model;
/**
* 专业类
* @author 杰大大
*
*/
public class Subject {
//学科的名称，学科编号，学制年限
private String subjectName;
private String subjectNum;
private int subjectLife;
private Student student[];
private int studentNum;
//带参构造实现对属性的全部赋值
public Subject(String subjectName,String subjectNum,int subjectLife)
{
  this.setSubjectName(subjectName);
  this.setSubjectNum(subjectNum);
  this.setSubjectLife(subjectLife);
}
public Subject(String subjectName,String subjectNum,int subjectLife,Student student[],int studentNum)
{
  this.setSubjectName(subjectName);
  this.setSubjectNum(subjectNum);
  this.setSubjectLife(subjectLife);
  this.setStudent(student);
  this.setStudentNum(studentNum);
}
//无参构造
public Subject()
{

}

public String getSubjectName() {
  return subjectName;
}
public void setSubjectName(String subjectName) {
  this.subjectName = subjectName;
}
public String getSubjectNum() {
  return subjectNum;
}
public void setSubjectNum(String subjectNum) {
  this.subjectNum = subjectNum;
}
public int getSubjectLife() {
  return subjectLife;
}
public void setSubjectLife(int subjectLife) {
  if(subjectLife<=0)
  {
   return;
  }
  else
  this.subjectLife = subjectLife;

}

//专业介绍的方法名称，编号，年限
/*public void info()
{
  //String str="专业信息如下\n专业名称   "+this.getSubjectName()+"\n专业编号    "+this.getSubjectNum()+"\n学制年限     "+this.getSubjectLife();
  //return str;
  System.out.println("专业名称 "+this.getSubjectName());
  System.out.println("专业编号 "+this.getSubjectNum());
  System.out.println("专业年限 "+this.getSubjectLife());

}*/
/**
* 增加学生，判断student是不是实例化了
* @return 学生的
*/
public Student[] getStudent() {
  if(student==null)
  {
   this.student=new Student[200];
  }
  return student;
}
public void setStudent(Student[] student) {
  this.student = student;
}
public int getStudentNum() {
  return studentNum;
}
public void setStudentNum(int studentNum) {
  this.studentNum = studentNum;
}
public String info() {
  String str="专业信息如下:\n专业名称   "+this.getSubjectName()+"\n专业编号    "+this.getSubjectNum()+"\n学制年限     "+this.getSubjectLife();
    return str;
}
public void addNum(Student student)
{
  int i;
  for(i = 0;i<this.getStudent().length;i++)
  {
   if(this.getStudent()[i]==null)
   {
    this.getStudent()[i]=student;
    break;
   }
  }
  this.setStudentNum(i+1);
}
}

student类的完整代码

package com.jiedada.model;

public class Student {
//姓名，年龄，性别，学号
private String studentNo;
private String studentName;
private String studentSex;
private int studentAge;
private Subject studentSubject;
//无参构造
public Student() {

}
/*public Student(String studentNo, String studentName, String studentSex, int studentAge) {
  this.studentNo = studentNo;
  this.studentName = studentName;
  this.studentSex = studentSex;
  this.studentAge = studentAge;
}*/

//有参构造
public Student(String studentNo,String studentName,String studentSex,int studentAge)
{
  this.setStudentNo(studentNo);
  this.setStudentName(studentName);
  this.setStudentSex(studentSex);
  this.setStudentAge(studentAge);
}
//有参构造而且返回全部属性
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.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) {
  if(studentSex=="男"|studentSex=="女")
  this.studentSex = studentSex;
  else
   this.studentSex="性别错误";
}
public int getStudentAge() {
  return studentAge;
}
public void setStudentAge(int studentAge) {
  if(studentAge>=10&studentAge<=100)
  this.studentAge = studentAge;
  else
   this.studentAge=18;
}
//在创建类的Get是要把类实例化
public Subject getStudentSubject() {
  if(studentSubject==null)
  {
   this.studentSubject=new Subject();
  }
  return studentSubject;
}

public void setStudentSubject(Subject studentSubject) {
this.studentSubject = studentSubject;
}

/**
* 这是学生自我介绍得等等
* @return 姓名，学号，姓名，年龄,所在专业，专业年龄
*/
public String introduction()
{
  String str="学生信息如下:\n我的名字是 "+this.getStudentName()+"\n我的学号为 "
+this.getStudentNo()+"\n性别为 "+this.getStudentSex()+"\n年龄为 "+this.studentAge
+"\n所在学科为 "+this.getStudentSubject().getSubjectName()+"\n学科的年制 "+this.getStudentSubject().getSubjectLife();
  return str;
}
/**
* 学生的自我介绍的方法
* @param subjectName
* @param subjectLife
* @return 姓名，学号，姓名，年龄，所在专业，专业年龄
*/
public String introduction(String subjectName,int subjectLife)
{
  String str="学生信息如下:\n我的名字是 "+this.getStudentName()+"\n我的学号为 "
    +this.getStudentNo()+"\n性别为 "+this.getStudentSex()+"\n年龄为 "+this.studentAge
    +"\n所在学科为 "+subjectName+"\n学科的年制 "+subjectLife;
     return str;
}
/**
* 介绍自己
* @param subject
* @return 姓名，学号，姓名，年龄，所在专业，专业年龄
*/
public String introduction(Subject subject)
{
  String str="学生信息如下:\n我的名字是 "+this.getStudentName()+"\n我的学号为 "
    +this.getStudentNo()+"\n性别为 "+this.getStudentSex()+"\n年龄为 "+this.studentAge
    +"\n所在学科为 "+subject.getSubjectName()+"\n学科的年制 "+subject.getSubjectLife();
     return str;
}

}

test类的完整代码

package com.jiedada.test;

import com.jiedada.model.Student;
import com.jiedada.model.Subject;

public class SchoolTest {
public static void main(String[] args) {
  // 调试Subject
  Subject sub = new Subject("计算机科学", "J0001", 4);
  System.out.println(sub.info());
  System.out.println("==============================");
  Student stu1=new Student("S01","张三","无",5,sub);
  System.out.println(stu1.introduction());
  System.out.println("==============================");
  Student stu2=new Student("S02","李四","女",20);
  System.out.println(stu2.introduction("计算机科学学院", 4));
  System.out.println("==============================");
  Student stu3=new Student("S03","王五","男",21);
  System.out.println(stu3.introduction(sub));
  sub.addNum(stu1);
  sub.addNum(stu2);
  sub.addNum(stu3);
  System.out.println("选择 "+sub.getSubjectName()+"专业的人数为 "+sub.getStudentNum());
}
}