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 {@Overridepublic 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("---------------------------");}@Overridepublic 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();}
}