Java程序設計 北京大學 Week4互評作業

java程序設計mooc攻略

單元測驗	互評作業	考試
week1測驗		2019冬期中測驗
week2測驗	week2互評作業	2019冬期末測驗
week3測驗	week3互評作業
week4測驗	week4互評作業
week5測驗	week5互評作業
week6測驗	week6互評作業
week7測驗	week7互評作業
week8測驗	week8互評作業
week9測驗	week9互評作業
week10測驗	week10互評作業
week11測驗	吃不消，我自己是github上找了個項目上去

編寫一個小的程序，其中定義一些接口、類、抽象類，定義它們的成員（字段及方法）， 要求使用使用setter/getter, static, final, abstract，@Override等語法要素，並寫一個main函數來使用它們。這些類、接口可以是圍繞以下選題之一

飛翔世界：來一次飛翔接力（即多個可飛翔的對象依次調用）;

動物世界：來一次吃西瓜大賽;

圖書館：模擬一天的借閱過程;

學校：模擬選課過程;

等等

要求寫個簡要說明。

文件結構

.
├── Game.java
├── animals
│   ├── Animal.java
│   ├── Elephant.java
│   ├── Lion.java
│   ├── Monkey.java
│   ├── Pig.java
│   └── Rabbit.java
└── prop
    ├── Plate.java
    ├── Record.java
    └── Watermelon.java

每個文件的代碼

Game.java

import animals.*;
import prop.Plate;
import prop.Record;
import prop.Watermelon;

import java.util.Arrays;
import java.util.Random;
import java.util.Vector;

public class Game {

    public static void main(String[] args) {
        System.out.println("觀衆朋友們，大家好，一年一度的吃西瓜大賽又開始了。");
        System.out.println("讓我們歡迎我們今年的選手：");
        System.out.println("");
        try {
            Thread.sleep(1000);
        } catch (InterruptedException e) { }
        Vector<Animal> players = new Vector<Animal>();
        players.add(new Rabbit(10));
        players.add(new Pig(30));
        players.add(new Elephant(28));
        players.add(new Monkey(18));
        players.add(new Lion(24));
        for (Animal each : players) {
            System.out.println(each.getName() + ": " + each.say());
            try {
                Thread.sleep(1000);
            } catch (InterruptedException e) { }
        }
        Plate<Watermelon> p;
        Record[] record = new Record[5];
        int index = 0;
        System.out.println("");
        for (Animal each : players) {
            System.out.println("好的，接下來有請" + each.getName() + "開始吃西瓜，計時開始");
            p = new Plate<>(10);
            Random seed = new Random(1);
            for (int i = 0; i < 10; i++) {
                p.add(new Watermelon(seed.nextInt(20)));
            }
            for (int i = 0; i < 10; i++) {
                System.out.print(".");
                System.out.flush();
                try {
                    Thread.sleep(1000);
                } catch (InterruptedException e) { }
            }
            record[index] = new Record(each.getName(), each.eatWatermelon(p));
            System.out.println("");
            System.out.printf("總共花費了%.2fs的時間。非常不錯的成績\n", record[index].getTime());
            System.out.println("");
            index++;
        }
        Arrays.sort(record);
        System.out.println("接下來公佈成績：");
        try {
            Thread.sleep(3000);
        } catch (InterruptedException e) { }
        for (int i = 0; i < 5; i++) {
            System.out.print("第" + (i + 1) + "名是");
            try {
                Thread.sleep(1000);
            } catch (InterruptedException e) { }
            System.out.println(record[i].getName());
        }
    }

}

prop/Plate.java

package prop;

import java.util.concurrent.ArrayBlockingQueue;

public class Plate<T> {
    private ArrayBlockingQueue<T> container;

    public Plate(int limits) {
        this.container = new ArrayBlockingQueue<T>(limits);
    }

    public boolean add(T one) {
        return container.add(one);
    }

    public T reduce() {
        return container.poll();
    }

    public boolean isEmpty() {
        return container.isEmpty();
    }

    public T getOne() {
        return container.peek();
    }

}

prop/Record.java

package prop;

public class Record implements Comparable<Record>{

    public Record(String name, double time) {
        this.name = name;
        this.time = time;
    }

    public String getName() {
        return name;
    }

    public double getTime() {
        return time;
    }

    @Override
    public int compareTo(Record o) {
        return Double.compare(this.time,o.time);
    }

    private String name;
    private Double time;

}

prop/Watermelon.java

package prop;

public class Watermelon {

    private final int size;

    public int getSize() {
        return size;
    }

    public Watermelon(int size) {
        this.size = size;
    }

}

aninals/Animals.java

package animals;

import prop.Plate;
import prop.Watermelon;

public abstract class Animal {
    abstract public String say();

    abstract public int getEatSpeed();
    public double eatWatermelon(Plate<Watermelon> plate) {
        int sum = 0;
        while (!plate.isEmpty()) {
            Watermelon w = plate.reduce();
            sum += w.getSize();
        }
        return sum*1.0/getEatSpeed();
    }

    abstract public String getName();
}

animals/Elephant.java

package animals;

public class Elephant extends Animal {

    public Elephant(int eatSpeed) {
        name = "大象";
        this.eatSpeed = eatSpeed;
    }

    @Override
    public String getName() {
        return name;
    }

    @Override
    public int getEatSpeed() {
        return eatSpeed;
    }

    @Override
    public String say() {
        return "我的鼻子可以捲起許多西瓜。";
    }

    final private String name;
    private int eatSpeed;

}

aninals/Lion.java

package animals;

public class Lion extends Animal {

    public Lion(int eatSpeed) {
        name = "獅子";
        this.eatSpeed = eatSpeed;
    }

    @Override
    public String getName() {
        return name;
    }

    @Override
    public int getEatSpeed() {
        return eatSpeed;
    }

    @Override
    public String say() {
        return "我是森林之王。";
    }

    final private String name;
    private int eatSpeed;

}

aninals/Monkey.java

package animals;

public class Monkey extends Animal {

    public Monkey(int eatSpeed) {
        name = "猴子";
        this.eatSpeed = eatSpeed;
    }

    @Override
    public String getName() {
        return name;
    }

    @Override
    public int getEatSpeed() {
        return eatSpeed;
    }

    @Override
    public String say() {
        return "我要讓你看看我吃的有多快。";
    }

    final private String name;
    private int eatSpeed;

}

aninals/Pig.java

package animals;

public class Pig extends Animal {

    public Pig(int eatSpeed) {
        name = "豬";
        this.eatSpeed = eatSpeed;
    }

    @Override
    public String getName() {
        return name;
    }

    @Override
    public int getEatSpeed() {
        return eatSpeed;
    }

    @Override
    public String say() {
        return "我有一個超級大的胃。";
    }

    final private String name;
    private int eatSpeed;

}

aninals/Rabbit.java

package animals;

public class Rabbit extends Animal {

    public Rabbit(int eatSpeed) {
        name = "兔子";
        this.eatSpeed = eatSpeed;
    }

    public String getName() {
        return name;
    }

    @Override
    public int getEatSpeed() {
        return eatSpeed;
    }

    @Override
    public String say() {
        return "我喜歡胡蘿蔔。";
    }

    final private String name;
    private int eatSpeed;

}

程序啓動

運行Game.java的main函數。