feat(class15): 封装设计，暴露方法

- 在 class15.capsulation 包中添加 Student 类，实现学生信息封装和成绩计算功能
- 在 class15.thisdemo 包中添加 Student 类，演示 this 关键字的使用
- 添加 Test 类进行功能测试

src/class15/capsulation/Student.java

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+package class15.capsulation;
+
+public class Student {
+    String name;
+    private int age;
+    private double chinese;
+    private double math;
+    public String getName()
+    {
+        return this.name;
+    }
+    public void setName(String name){
+        this.name = name;
+    }
+//    两门成绩的设置和读取方法
+    public void setChinese(double chinese){
+        if(chinese>=0 && chinese<=100){
+            this.chinese = chinese;
+        }
+        else{
+            System.out.println("请输入正确的成绩");
+        }
+    }
+    public double getChinese(){
+        return this.chinese;
+    }
+    public void setMath(double math){
+        if(math>=0 && math<=100){
+            this.math = math;
+        }
+        else{
+            System.out.println("请输入正确的成绩");
+        }
+    }
+    public double getMath(){
+        return this.math;
+    }
+    public int getAge()
+    {
+        return this.age;
+    }
+    public void setAge(int age){
+        if(age>0 && age<=100){
+            this.age = age;
+        }else {
+            System.out.println("年龄数据非法！");
+        }
+    }
+    public void printAllScore()
+    {
+        System.out.println(name+"的总成绩是："+(chinese+math));
+    }
+    public void printAverageScore()
+    {
+        System.out.println(name+"的平均成绩是："+(chinese+math)/2);
+    }
+}

src/class15/capsulation/Test.java

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+package class15.capsulation;
+
+public class Test {
+    public static void main(String[] args) {
+    Student s1 = new Student();
+    s1.setAge(19);
+    s1.setChinese(90);
+    s1.setMath(80);
+    System.out.println(s1.getAge());
+    System.out.println(s1.getChinese());
+    System.out.println(s1.getMath());
+    s1.printAllScore();
+    s1.printAverageScore();
+    }
+}

src/class15/thisdemo/Student.java

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+package class15.thisdemo;
+
+public class Student {
+    String name;
+    public void print(){
+        //this 是一个变量，在方法中，用于拿到当前对象
+        //哪个对象调用的print方法，this就代表哪个对象
+        System.out.println(this);
+    }
+    public void printHobby(String name){
+        System.out.println(this.name + "喜欢" + name);
+    }
+}

src/class15/thisdemo/Test.java

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+package class15.thisdemo;
+
+public class Test {
+    public static void main(String[] args) {
+        Student s1 = new Student();
+        s1.name = "张三";
+        //地址值相同
+        s1.print();
+        System.out.println(s1);
+
+        Student s2 = new Student();
+        s2.print();
+        System.out.println(s2);
+
+        Student s3 = new Student();
+        s3.name="汪苏泷";
+        s3.printHobby("唱歌！");
+        //this指向对象本身，对象中的变量与方法变量名冲突时，this可以解决变量冲突问题，指向方法中的变量，this.变量名
+    }
+}