feat(class15): 类，无参构造方法，有参构造方法，创建对象

- 在 constructor包中添加 Student 类，包含多个构造方法和属性
- 在 object 包中添加 Student 类，包含成绩相关方法
- 添加 Test 类测试 constructor 包中的 Student 类- 添加 Test2 类测试 object包中的 Student 类

src/class15/constructor/Student.java

@@ -0,0 +1,21 @@
+package class15.constructor;
+
+public class Student {
+    String name;
+    int age;
+    char sex;
+    public Student(){
+        System.out.println("无参构造方法");
+    }
+    public Student(String n){
+        System.out.println("有参构造方法");
+        name = n;
+    }
+    public Student(String n ,int a,char s){
+        System.out.println("有参构造方法");
+        name = n;
+        age = a;
+        sex = s;
+    }
+
+}

src/class15/constructor/Test.java

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+package class15.constructor;
+
+public class Test {
+    public static void main(String[] args) {
+        Student s1 = new Student();
+        Student s2 = new Student("小王");
+        System.out.println(s1.name);
+        System.out.println(s2.name);
+        System.out.println("==========");
+
+
+        Student t1 = new Student();
+        t1.name = "石轩";
+        t1.age = 18;
+        t1.sex = '男';
+        System.out.println(t1.name);
+        System.out.println(t1.age);
+        System.out.println(t1.sex);
+
+        System.out.println("==========");
+        Student t2 = new Student("d老师", 18,'男');
+        System.out.println(t2.name);
+        System.out.println(t2.age);
+        System.out.println(t2.sex);
+    }
+}

src/class15/object/Student.java

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+package class15.object;
+
+public class Student {
+    String name;
+    double chinese;
+    double math;
+    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/object/Test2.java

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+package class15.object;
+
+public class Test2 {
+    public static void main(String[] args) {
+        Student s1 = new Student();
+        s1.name = "波妞";
+        s1.chinese = 100;
+        s1.math = 100;
+        s1.printAllScore();
+        s1.printAverageScore();
+
+        Student s2 = new Student();
+        s2.name = "小王";
+        s2.chinese = 100;
+        s2.math = 100;
+        s2.printAllScore();
+        s2.printAverageScore();
+    }
+
+}