学习java中的interface接口

1.了解接口

java提供了一个关键字interface，用这个关键字我们可以定义出一个特殊的结构：接口

格式：

public interface 接口名{
//成员变量（常量）
//成员方法（抽象方法）
}

注意：接口不能创建对象，接口是用来被类实现（implements）的，实现接口的类被称为实现类。

书写格式：

public class 实现类 implements 接口1，接口2.....{

}

一个类中可以实现多个接口，实现类实现多个接口，必须重写完全部接口的抽象方法，否则实现类需要定义成抽象类。

2.接口的好处

弥补了单继承的不足，一个类可以同时实现多个接口。

让程序可以面向接口编程，让程序员可以灵活方便的切换各种业务实现。

3.接口案例-学生管理

package com.web807.interface_study;

import java.util.ArrayList;

public class ClassManager {
    private ArrayList<Student> students = new ArrayList<Student>();
    private StudentOperator studentOperator = new StudentOperatorImpl();

    public ClassManager() {
        Student student1 = new Student("Tom", '男', 98);
        Student student2 = new Student("jerry", '男', 99);
        Student student3 = new Student("merry", '女', 100);
        Student student4 = new Student("lily", '女', 97);
        students.add(student1);
        students.add(student2);
        students.add(student3);
        students.add(student4);
    }

    //打印全班全部学生的信息
    public void printInfo() {
        studentOperator.printAll(students);
    }

    //打印全班全部学生的平均分
    public void score() {
        studentOperator.printScore(students);
    }
}

package com.web807.interface_study;

public class Student {
    private String name;
    private char sex;
    private double score;

    public Student() {
    }

    public Student(String name, char sex, double score) {
        this.name = name;
        this.sex = sex;
        this.score = score;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public char getSex() {
        return sex;
    }

    public void setSex(char sex) {
        this.sex = sex;
    }

    public double getScore() {
        return score;
    }

    public void setScore(double score) {
        this.score = score;
    }
}

package com.web807.interface_study;

import java.util.ArrayList;

public interface StudentOperator {
    void printAll(ArrayList<Student> students);
    void printScore(ArrayList<Student> students);

}

package com.web807.interface_study;

import java.util.ArrayList;

public class StudentOperatorImpl implements StudentOperator {
    @Override
    public void printAll(ArrayList<Student> students) {
        System.out.println("--------打印全部学生信息----------");
        int count1 = 0;
        int count2 = 0;
        for (int i = 0; i < students.size(); i++) {
            Student student = students.get(i);
            System.out.println("学生姓名：" + student.getName());
            System.out.println("学生性别：" + student.getSex());
            System.out.println("学生成绩：" + student.getScore());
            if (student.getSex() == '男') {
                count1++;
            } else {
                count2++;
            }
            System.out.println("-*-----------*-");
        }
        System.out.println("男生人数:" + count1);
        System.out.println("女生人数:" + count2);
        System.out.println("---------------------------");
    }

    @Override
    public void printScore(ArrayList<Student> students) {
        System.out.println("--------打印全部学生的平均成绩----------");
        double MaxScore = students.get(0).getScore();
        double MinScore = students.get(0).getScore();
        double sum = 0;
        for (int i = 0; i < students.size(); i++) {
            Student student = students.get(i);
            if (student.getScore() > MaxScore) {
                MaxScore = student.getScore();
            }
            if (student.getScore() > MinScore) {

                MinScore = student.getScore();
            }
            sum += student.getScore();
        }
        double average = (sum - MaxScore - MinScore) / students.size();
        System.out.println("平均成绩：" + average);
        System.out.println("-------------------------------");
    }
}

package com.web807.interface_study;

public class Main {
    public static void main(String[] args) {
        // 创建实现了接口的对象
        ClassManager classManager = new ClassManager();
        classManager.printInfo();
        classManager.score();


    }
}