java练习题之接口interface练习

15：仔细阅读以下代码，完成//1、//2、//3、//4 处程序。

Animal []as={new Cat,new Dog,new Wolf};

int count=0;

for(int i=0;i<as.length;i++){

?if(as[i] instanceof Dog){

as[i].eat();

as[i].play();

count++;

}else if(as[i] instanceof ?Cat){

as[i].eat();

as[i].play();

count++

}else{

as[i].eat

count++

}

}

System.out.println(count);

16：编程：定义一个接口 MathTool，接口中有三个抽象方法如下：

“long fact(int?m);”方法的功能为：求参数的阶乘

“long intPower(int m , int n)”方法的功能为：求m 的n 次方

“boolean findFactor(int?m,int?n)”方法的功能为：判断参数的和是否大于 100

定义类实现接口，编写应用程序，调用接口中的 3 个方法，并将调用方法的结果输出。

17：编程：把继承练习题中形状改为接口?

package com.by.homework3.figure;

public interface Figure {
????public abstract void qiuzhouchang();
????public abstract void qiumianji();
}



package com.by.homework3.figure;

public class Circle implements Figure{
????int banjin;

????public Circle(int banjin) {
????????this.banjin = banjin;
????}

????@Override
????public void qiuzhouchang() {
????????Double zhouchang=2*3.14*banjin;
????????System.out.println("圆的周长："+zhouchang);
????}

????@Override
????public void qiumianji() {
????????Double mianji=3.14*banjin*banjin;
????????System.out.println("圆的面积："+mianji);
????}
}



package com.by.homework3.figure;

public class Square implements Figure{
????int bianchang;

????public Square(){

????}
????public Square(int bianchang) {
????????this.bianchang = bianchang;
????}

????public void qiuzhouchang(){
????????int zhouchang=bianchang*4;
????????System.out.println("正方形的周长:"+zhouchang);
????}
????public void qiumianji(){
????????int mianji=bianchang*bianchang;
????????System.out.println("正方形的面积:"+mianji);
????}
}

18：定义一个接口MediaPlayer,表示一个家庭影院的设备，MediaPlayer中包含play(),stop(),open()，三个方法分别表示播放、停止和开仓功能。

MediaPlayer有三个实现类，分别是：DVDPlayer，表示DVD播放器；CDPlayer，表示CD播放器； TapePlayer,表示收音机（播放磁带）。

创建一个遥控器Controller类。该遥控器有三个频道，可以分别控制三个设备。部分代码如下：

要求：

①完成MediaPlayer接口及其实现类代码。

package com.by.homework6.mediaPlayer;

interface MediaPlayer{
????void play();
????void open();
????void stop();

}


class DVDPlayer implements MediaPlayer{
????@Override
????public void play() {

????}

????@Override
????public void open() {

????}

????@Override
????public void stop() {

????}
}

class CdPLayer implements MediaPlayer{
????@Override
????public void play() {

????}

????@Override
????public void open() {

????}

????@Override
????public void stop() {

????}
}

class TapePlayer implements MediaPlayer{
????@Override
????public void play() {

????}

????@Override
????public void open() {

????}

????@Override
????public void stop() {

????}
}




class Controller{
????private MediaPlayer[] players;
????public Controller(){

????}

????public void play(int i){
????????players[i].play();
????}

}

public class MediaPlayerTest {
????public static void main(String[]args){

????}
}

②把Controller补充完整，完善其构造方法，并为其增加stop(int i)和open(int i)方法

19：定义一个Performer接口，表示一个演员，接口中定义perform方法，表示表演。为这个接口提供若干实现类：singer，表示歌手；Dancer，表示舞蹈演员；Player，表示演奏者。

定义一个Program类，表示一个节目。每一个节目需要多个演员配合，因此每一个Program类中都包含一个属性：Performer数组，表示表演这个节目所需要的演员。

给出Program的部分代码：

class Program{

private Performer[] ps;

public ?Program(){

ps=new Performer[3];

ps[0]=new Singer();

ps[1]=new Dancer();

ps[2]=new Player();

}

}

在现有代码的基础上，为Program增加一个show方法，在这个方法中，调用所有的表演这个节目的所有Performer的perform方法。

?Performer 接口：
public interface Performer {
????/**表演*/
????public abstract void perform();
}
Singer类：
public class Singer implements Performer {
????public void perform() {
????????System.out.println("歌手在表演");
????}
}
????Dancer 类：
public class Dancer implements Performer {
????public void perform() {
????????System.out.println("舞蹈演员在表演");
????}
}
Player类：
public class Player implements Performer {
????public void perform() {
????????System.out.println("演奏者在表演");
????}
}
????Program 类：
public class Program {
????private Performer[] ps;
????public Program(){
????????ps = new Performer[3];
????????ps[0] = new Singer();
????????ps[1] = new Dancer();
????????ps[2] = new Player();
????}
????public void show(){
????????for (int i = 0; i < ps.length; i++) {
????????????ps[i].perform();
????????}
????}
}
????PerformerTest 测试类：
public class PerformerTest {
????public static void main(String[] args) {
????????Program program = new Program();
????????program.show();
????}
}

20：定义一个学生类，属性为：姓名、年龄、成绩、头发数量

定义比较排序规则：

根据成绩从大到小排

如果成绩相同，根据头发数量从小到大排

如果头发数量也相同，根据年龄从小到大排

定义测试类，创建学生数组，合理创建若干学生对象，验证排序比较规则

提示：在compare方法中结合嵌套if分支

提交要求：把代码及运行截图放入word文档提交

?Student 类：
public class Student {
????private String name;
????private int age;
????private double score;
????private int hairNum;
????public Student() {
????}
????public Student(String name, int age, double score,int hairNum) {
????????this.name = name;
????????this.age = age;
????????this.score = score;
????????this.hairNum = hairNum;
????}
????public String getName() {
????????return name;
????}
????public void setName(String name) {
????????this.name = name;
????}
????public int getAge() {
????????return age;
????}
????public void setAge(int age) {
????????this.age = age;
????}
????public double getScore() {
????????return score;
????}
????public void setScore(double score) {
????????this.score = score;
????}
????public int getHairNum() {
????????return hairNum;
????}
????public void setHairNum(int hairNum) {
????????this.hairNum = hairNum;
????}
}
????StudentCompare 类：
public class StudentCompare implements Comparator<Student> {
????public int compare(Student o1, Student o2) {
????????if(o1.getScore() < o2.getScore()){
????????????return 1;
????????}else if(o1.getScore() > o2.getScore()){
????????????return -1;
????????}else {
????????????//如果成绩相等，头发少的在前
????????????if(o1.getHairNum() > o2.getHairNum()){
????????????????return 1;
????????????}else if(o1.getHairNum() < o2.getHairNum()){
????????????????return -1;
????????????}else{
????????????????if(o1.getAge() < o2.getScore()){
????????????????????return 1;
????????????????}else if(o1.getAge() > o2.getScore()){
????????????????????return -1;
????????????????}
????????????}
????????????return 0;
????????}
????}
}
????CompareTest 类：
public class CompareTest {
????public static void main(String[] args) {
????????Student[] students = {new Student("小白",23,100,123456),
????????????????new Student("小红",22,88,111111),
????????????????new Student("大红",23,88,111111),
????????????????new Student("小明",20,100,130000),
????????????????new Student("小美",21,90,130000)};
????????Arrays.sort(students, new StudentCompare());
????????//输出排序结果
????????for (int i = 0; i < students.length; i++) {
????????????System.out.println(students[i].getName()+" ?"+students[i].getAge() +" ?"
????????????????????+students[i].getScore() + " " + students[i].getHairNum());
????????}
????}
}