JAVA课堂练习
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课堂练习4:
编写代码模拟手机与SIM卡的组合关系。
要求:
SIM卡类负责创建SIM卡;
Phone类负责创建手机;
手机可以组合一个SIM卡;
手机可以更换其中的SIM卡。
public class TestPhone {public static void main(String[] args) {Phone phone = new Phone();Sim sim1 = new Sim(12345);System.out.print("号码为:"+phone.use(sim1)+"\n");Sim sim2 = new Sim(67890);System.out.print("更换号码为:"+phone.use(sim2));}}class Phone{long use(Sim sim1) {Sim sim = sim1;return sim.Sim(); }}class Sim{long sim;Sim(long number) {sim = number;}long Sim() {return sim;}}
课堂练习5:
public class Test {public static void main(String[] args) {CPU cpu = new CPU();cpu.setSpeed(2200);HardDisk disk = new HardDisk();disk.setAmount(200);PC pc = new PC();pc.setCPU(cpu);pc.setHardDisk(disk);pc.show();}}class PC{CPU cpu;HardDisk HD;void setCPU(CPU c) {cpu = c;}void setHardDisk(HardDisk h) {HD = h;}void show() {System.out.println("CPU的速度:"+cpu.getSpeed());System.out.print("硬盘的容量:"+HD.getAmount());}}class CPU{int speed;void setSpeed(int m) {speed = m;}int getSpeed() {return speed;}}class HardDisk{int amount;void setAmount(int m) {amount = m;}int getAmount() {return amount;}}
课堂练习6:
– 定义一个圆类(Circle),其所在的包为bzu.info.software;定义一个圆柱类Cylinder,其所在的包为bzu.info.com;定义一个主类A,其所在的包也为bzu.info.com,在A中生成一个Cylinder对象,并输出其体积。编译并运行该类。
– 试着改变求体积方法的访问权限,查看并分析编译和运行结果
– 把Cylinder类和A类置于不同的包中,通过对求体积方法设置不同的访问权限,查看并分析编译和运行结果
package bzu.info.com;import bzu.info.software.Circle;public class A {public static void main(String[] args) {Circle circle = new Circle(2.0);Cylinder cylinder = new Cylinder(3.0,circle);System.out.println("圆柱的体积:"+cylinder.volume());}}
package bzu.info.com;import bzu.info.software.Circle;public class Cylinder {double h;Circle circle;public Cylinder(double d, Circle circle2) {h = d;circle = circle2;}double volume() {return circle.area()*h;}}
package bzu.info.software;public class Circle {double r;public Circle(double r){this.r = r;}public double area() {double area = 3.14*r*r;return area;}}
更改volume()的访问权限为public或protected,结果不受影响。更改为private,运行结果如下:
把Cylinder类和A类置于不同的包中:
当volume()访问权限为public时,成功运行。更改为protected,default或private时,结果如下:
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