Java入门——day53

1.Cat类

定义一个Cat类，拥有静态数据成员numOfCats，记录Cat的个体数目；静态成员函数getNumOfCats()，读取numOfCats。设计程序测试这个类，体会静态数据成员和静态成员函数的用法。

//Cat类
public class Cat {
    private static int numOfCats=0; //记录Cat的个体数目
    Cat(){
        numOfCats++;
    }
    public static int getNumOfCats() {
        return numOfCats;
    }
    public static void main(String[] args) {
        int n=6;
        Cat cat[]=new Cat[n];
        for(int i=0;i<n;i++) {
            cat[i]=new Cat();
            System.out.println("There are "+Cat.getNumOfCats()+" cat.");
        }
    }
}

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 2.定义静态变量n，fn1()中对n值加1，在主函数中，加十次，显示n的值。

package com.practice;
public class Test {
    public static int n=0;
    public static void main(String[] args) {
        for(int i=0;i<10;i++) {
            n++;
            System.out.println("n的值为："+n);
        }
    }
}

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3.定义Boat和Cat两个类，二者都有weight属性，定义函数getTotalWeight()，计算二者的重量和。

//Boat类
class Boat{
    private double weight; //重量
    Boat(){
    }
    public Boat(double weight) {
        this.weight = weight;
    }
    public double getWeight() {
        return weight;
    }
    public void setWeight(double weight) {
        this.weight = weight;
    }
}
//Cat类
class Cat{
    private double weight; //重量
    public Cat() {
    }
    public Cat(double weight) {
        this.weight = weight;
    }
    public double getTotalWeight(Boat b) {
        return weight+b.getWeight();
    }
    public double getWeight() {
        return weight;
    }
    public void setWeight(double weight) {
        this.weight = weight;
    }
}
public class Test {
    public static void main(String[] args) {
        Boat b=new Boat(8);
        Cat c=new Cat(5);
        System.out.println("Boat重量："+b.getWeight());
        System.out.println("Cat重量："+c.getWeight());
        System.out.println("重量之和："+c.getTotalWeight(b));
    }
}