Java封装综合案例

学生信息管理系统设计
```java
package me.feihong.model;

public class Subject {
	// 成员属性：学科名称、学科编号、学制年限、报名选修的学生个数
	private String subjectName;
	private String subjectNo;
	private int subjectLife;
	private Student[] myStudents;
	private int studentNum;

// 无参构造方法
public Subject() {

}

// 带参构造,实现对学科名称、编号、学制年限赋值
public Subject(String subjectName, String subjectNo, int subjectLife) {
	this.setSubjectName(subjectName);
	this.setSubjectNo(subjectNo);
	this.setSubjectLife(subjectLife);
}

public Subject(String subjectName, String subjectNo, int subjectLife,Student[] myStudents) {
	this.setSubjectName(subjectName);
	this.setSubjectNo(subjectNo);
	this.setSubjectLife(subjectLife);
	this.setMyStudents(myStudents);
}

public void setSubjectName(String subjectName) {
	this.subjectName = subjectName;
}

public String getSubjectName() {
	return this.subjectName;
}

public void setSubjectNo(String subjectNo) {
	this.subjectNo = subjectNo;
}

public String getSubjectNo() {
	return this.subjectNo;
}

// 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，则先进行初始化
 * @return
 */
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;
}

public int getSubjectLife() {
	return this.subjectLife;
}
/**
 * 专业介绍的方法
 * @return专业介绍相关信息，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
	int i;
	for(i=0;i<this.getMyStudents().length;i++) {
		if(this.getMyStudents()[i]==null) {
			stu.setStudentSubject(this);
			this.getMyStudents()[i]=stu;
			break;
		}
	}
	//2、将学生个数保存到studentNum
	this.studentNum=i+1;
}

}
```
```java
package me.feihong.model;

public class Student {
	// 成员属性:姓名，学号，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,实现对姓名  学号  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.setStudentSubject(studentSubject);
}

/**
 * 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;
}

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;
}

/**
 * 限制性别只能是“男”或者“女”，反之，强制赋值为“男”
 * 
 * @param studentSex
 */
public void setStudentSex(String studentSex) {
	if (studentSex == "男" || studentSex == "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
 */
public void setStudentAge(int studentAge) {
	if (studentAge < 10 || studentAge > 100)
		this.studentAge = 18;
	else
		this.studentAge = studentAge;
}

/**
 * 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()
			+ "\n专业编号:" + this.getStudentSubject().getSubjectNo();
	return str;
}

/**
 * 学生自我介绍的方法
 * 
 * @param subjectName
 * @param subjectLife
 * @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，专业编号
 */
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;
}

}
```
```java
package me.feihong.test;
import me.feihong.model.*;
public class SchoolTest {

public static void main(String[] args) {
	// TODO Auto-generated method stub
	//测试Subject
	Subject sub1=new Subject("计算机科学与应用","j0001",4);
	System.out.println(sub1.info());
	System.out.println("============================");
	//测试Student
	Student stu1=new Student("S01","张三","男",18,sub1);
	System.out.println(stu1.introduction());
	System.out.println("============================");
	Student stu2=new Student("S02","李四","女",17);
	System.out.println(stu2.introduction("计算机科学与应用", 4));
	System.out.println("============================");
	Student stu3=new Student("S03","王五","男",18);
	System.out.println(stu3.introduction(sub1));
	System.out.println("============================");
	//测试指定专业中到底有多少学生报名
	sub1.addStudent(stu1);
	sub1.addStudent(stu2);
	sub1.addStudent(stu3);
	System.out.println(sub1.getSubjectName()+"的专业中已有"+sub1.getStudentNum()+"学生进行了报名");
}

}
```