feat(class30,class32): 接口定义，实现类

- 在 class30 包中添加了接口 A 和 B，以及实现类 C 和测试类 Test
- 在 class32 包中添加了学生信息处理的接口和实现类，包括 ClassDataInter、ClassDataInterImpl1、ClassDataInterImpl2 和 Student 类
- 实现了学生信息的打印和平均分计算等功能

src/class30/A.java

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+package class30;
+
+public interface A {
+    // JDK8之前，接口中只能定义常量和抽象方法
+    String SCHOOL_NAME = "黑马程序员";
+//    public static final String SCHOOL_NAME = "黑马程序员"; // 可省略String的前缀
+//    public abstract void run(); // 可省略abstract
+    void run();
+    String go();
+}

src/class30/B.java

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+package class30;
+
+public interface B {
+    void play();
+}

src/class30/Test.java

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+package class30;
+
+public class Test {
+    public static void main(String[] args) {
+        C c = new C();
+        c.run();
+        c.go();
+        c.play();
+
+    }
+
+}
+//实现类实现多个接口，必须重写接口中所有的抽象方法
+class C implements A, B {
+
+    @Override
+    public void run() {
+
+    }
+
+    @Override
+    public String go() {
+        return "";
+    }
+
+    @Override
+    public void play() {
+
+    }
+}

src/class32/ClassDataInter.java

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+package class32;
+
+public interface ClassDataInter {
+    void printAllStudentInfos();
+    void printAverageScore();
+}

src/class32/ClassDataInterImpl1.java

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+package class32;
+
+public class ClassDataInterImpl1 implements ClassDataInter {
+    private final Student[] students;
+    public ClassDataInterImpl1(Student[] students) {
+        this.students = students;
+    }
+    @Override
+    public void printAllStudentInfos() {
+        for (Student student : students) {
+            System.out.println(student.getName() + " " + student.getSex() + " " + student.getScore());
+        }
+    }
+
+    @Override
+    public void printAverageScore() {
+        double sum = 0;
+        for (Student student : students) {
+            sum += student.getScore();
+        }
+        System.out.println("平均分是：" + sum / students.length);
+
+    }
+}

src/class32/ClassDataInterImpl2.java

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+package class32;
+public class ClassDataInterImpl2 implements ClassDataInter {
+    private final Student[] students;
+    public ClassDataInterImpl2(Student[] students) {
+        this.students = students;
+    }
+    @Override
+    public void printAllStudentInfos() {
+        int maleCount = 0;
+
+        for (Student student : students) {
+            if (student.getSex() == '男') {
+                maleCount++;
+            }
+        }
+        System.out.println("男性人数是：" + maleCount);
+        System.out.println("女性人数是：" + (students.length - maleCount));
+    }
+
+    @Override
+    public void printAverageScore() {
+        double sum = 0;
+        double max = students[0].getScore();
+        double min = students[0].getScore();
+        for (Student student : students) {
+            sum += student.getScore();
+            if (max < student.getScore()) {
+                max = student.getScore();
+            }
+            if (min > student.getScore()) {
+                min = student.getScore();
+            }
+        }
+        System.out.println("平均分是：" + (sum - max - min) / (students.length - 2));
+        System.out.println("最高分是：" + max);
+        System.out.println("最低分是：" + min);
+    }
+}

src/class32/Student.java

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+package class32;
+
+import lombok.AllArgsConstructor;
+import lombok.Data;
+import lombok.NoArgsConstructor;
+@Data
+@NoArgsConstructor
+@AllArgsConstructor
+public class Student {
+    private String name;
+    private char sex;
+    private double score;
+
+}

src/class32/Test.java

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+package class32;
+
+public class Test {
+    public static void main(String[] args) {
+        //目标：完成接口的小案例
+        //1.定义学生类，创建学生对象，封装学生数据，才能交给别人处理
+        //2.准备学生数据，目前我们自己造一些数据
+        Student[] students = new Student[10];
+        students[0] = new Student("小王", '男', 90);
+        students[1] = new Student("小王", '男', 90);
+        students[2] = new Student("小王", '男', 90);
+        students[3] = new Student("小王", '男', 90);
+        students[4] = new Student("小王", '男', 90);
+        students[5] = new Student("小王", '男', 90);
+        students[6] = new Student("小王", '男', 90);
+        students[7] = new Student("小王", '男', 90);
+        students[8] = new Student("小王", '男', 90);
+        students[9] = new Student("小王", '男', 90);
+        ClassDataInter cdi = new ClassDataInterImpl1(students);
+        cdi.printAllStudentInfos();
+        cdi.printAverageScore();
+        ClassDataInter cdi2 = new ClassDataInterImpl2(students);
+        cdi2.printAllStudentInfos();
+        cdi2.printAverageScore();
+    }
+}