4.3 实验练习

4.3.1 实例成员和类成员

class A{	
	float a;
	static float b;
	void setA(float a1){
		a=a1;
	}
	void setB(float b1){
		b=b1;
	}
	float getA(){
		return a;
	}
	float getB(){
		return b;
	}
	void inputA(){
		System.out.println(a);
	}
	static void inputB(){
		System.out.println(b);
	}
}
public class Ex4_3{
	public static void main(String args[]){
		A.b=100;
		A.inputB();
		A cat=new A();
		A dog=new A();
		cat.setA(180);
		cat.setB(380);
		cat.inputA();
		cat.inputB();
		dog.setA(300);
		dog.setB(800);
		dog.inputA();
		dog.inputB();
	}	
}

一下是错误的结果与正确的结果。错误的原因是：参数与成员变量都是同一个字母a.

 

4.3.2   公司和职员

class Employee{
	int age;
	void setAge(int m){
		age=m;
	}
	void showAge(){
		System.out.println("年龄："+age);
	}
}

class Corp{
	Employee secretary;
	void setSecretary(Employee emp){
		secretary=emp;
	}
	void showSecretaryAge(){
		secretary.showAge();
	}
}

public class Mainclass{
	public static void main(String args[]){
		Employee zhangLin=new Employee();
		zhangLin.setAge(21);
		Corp tomCorp=new Corp();
		tomCorp.setSecretary(zhangLin);
		System.out.println("tomCorp公司的秘书年龄：");
		tomCorp.showSecretaryAge();
		zhangLin.setAge(22);
		Employee jiangHua=new Employee();
		jiangHua.setAge(28);
		tomCorp.setSecretary(jiangHua);
		
		System.out.printf("zhangLin(年龄：%d)不再是公司的秘书了\n",zhangLin.age);
		System.out.println("tomCorp公司的秘书年龄：");
		tomCorp.showSecretaryAge();
	}
}