Java程序设计精编教程（5.14上机实践）

实验目的

本实验的目的是让学生掌握类变量与实例变量，以及类方法与实例方法的区别

实验要求

编写程序模拟两个村庄共同拥有一片森林。编写一个Village类，该类有一个静态的int型成员变量treeAmount用于模拟森林中树木的数量。在主类MainClass的main方法中创建两个村庄，一个村庄改变了treeAmount的值，另一个村庄查看treeAmount的值。

程序代码

Village.java

public class Village {
	static int treeAmount;	//模拟树林中树木的数量
	int peopleNumber;		//村庄的人数
	String name;			//村庄的名字
	Village(String s){
		name = s;
	}
	void treePlanting(int n) {
		treeAmount = treeAmount + n;
		System.out.println(name+"植树"+n+"棵");
	}
	void fellTree(int n) {
		if (treeAmount-n >= 0) {
			treeAmount = treeAmount - n;
			System.out.println(name+"伐树"+n+"棵");
		} else {
			System.out.println("无树木可伐");
		}
	}
	static int lookTreeAmount() {
		return treeAmount;
	}
	void addPeopleNumber(int n) {
		peopleNumber = peopleNumber + n;
		System.out.println(name+"增加了"+n+"人");
	}
}

MainClass.java

public class MainClass {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		Village zhaoZhuang,majiaHeZi;
		zhaoZhuang = new Village("赵庄");
		majiaHeZi = new Village("马家河子");
		zhaoZhuang.peopleNumber = 100;
		majiaHeZi.peopleNumber = 150;
		//用类名Village访问treeAmount，并赋值200
		Village.treeAmount = 200;
		int leftTree = Village.treeAmount;
		System.out.println("森林中有"+leftTree+"棵树");
		//zhaoZhuang调用treePlanting(int n)，并传值50
		zhaoZhuang.treePlanting(50);
		//majiaHezi调用lookTreeAmount()方法得到树木的数量
		leftTree = Village.lookTreeAmount();
		System.out.println("森林中有"+leftTree+"棵树");
		//majiaHeZi调用fellTree(int n)并向参数传值70
		majiaHeZi.fellTree(70);
		leftTree = Village.lookTreeAmount();
		System.out.println("森林中有"+leftTree+"棵树");
		System.out.println("赵庄的人口："+zhaoZhuang.peopleNumber);
		zhaoZhuang.addPeopleNumber(12);
		System.out.println("赵庄的人口："+zhaoZhuang.peopleNumber);
		System.out.println("马家河子的人口："+majiaHeZi.peopleNumber);
		majiaHeZi.addPeopleNumber(10);
		System.out.println("马家河子的人口："+majiaHeZi.peopleNumber);
	}

}

也可以合并到一起

public class MainClass {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		Village zhaoZhuang,majiaHeZi;
		zhaoZhuang = new Village("赵庄");
		majiaHeZi = new Village("马家河子");
		zhaoZhuang.peopleNumber = 100;
		majiaHeZi.peopleNumber = 150;
		//用类名Village访问treeAmount，并赋值200
		Village.treeAmount = 200;
		int leftTree = Village.treeAmount;
		System.out.println("森林中有"+leftTree+"棵树");
		//zhaoZhuang调用treePlanting(int n)，并传值50
		zhaoZhuang.treePlanting(50);
		//majiaHezi调用lookTreeAmount()方法得到树木的数量
		leftTree = Village.lookTreeAmount();
		System.out.println("森林中有"+leftTree+"棵树");
		//majiaHeZi调用fellTree(int n)并向参数传值70
		majiaHeZi.fellTree(70);
		leftTree = Village.lookTreeAmount();
		System.out.println("森林中有"+leftTree+"棵树");
		System.out.println("赵庄的人口："+zhaoZhuang.peopleNumber);
		zhaoZhuang.addPeopleNumber(12);
		System.out.println("赵庄的人口："+zhaoZhuang.peopleNumber);
		System.out.println("马家河子的人口："+majiaHeZi.peopleNumber);
		majiaHeZi.addPeopleNumber(10);
		System.out.println("马家河子的人口："+majiaHeZi.peopleNumber);
	}

}
class Village {
	static int treeAmount;	//模拟树林中树木的数量
	int peopleNumber;		//村庄的人数
	String name;			//村庄的名字
	Village(String s){
		name = s;
	}
	void treePlanting(int n) {
		treeAmount = treeAmount + n;
		System.out.println(name+"植树"+n+"棵");
	}
	void fellTree(int n) {
		if (treeAmount-n >= 0) {
			treeAmount = treeAmount - n;
			System.out.println(name+"伐树"+n+"棵");
		} else {
			System.out.println("无树木可伐");
		}
	}
	static int lookTreeAmount() {
		return treeAmount;
	}
	void addPeopleNumber(int n) {
		peopleNumber = peopleNumber + n;
		System.out.println(name+"增加了"+n+"人");
	}
}