The relationship between class and class - inheritance included dependent practice

1, students enter the room to use the computer

There are computer startup, shutdown, use the form

Computer class:

package com.stu_computer;

public  class Computer {
     // attributes 
    Private Boolean isUsed = false ; // if false to be off; power-on state is true for the 
    Private  int Number;
     // Method 
    public Boolean isUsed () {
         return isUsed;
    }
    public int getNumber() {
        return number;
    }
    // Constructors 
    public Computer () {}
     public Computer ( int Number) {
         the this .number = Number;
    }
    //被开机的方法
    public void beOn(Computer computer){
        System.out.println(this.number+"号电脑开机啦");
        computer.isUsed = true;
    }
    //被关机的方法
    public void beUsing(Computer computer){
        System.out.println(this.number+"号电脑正在使用中");
        }
    //被开机的方法
    public void beOff(Computer computer){
        System.out.println(this.number+"号电脑关机啦");
        computer.isUsed = false;
        }
}

机房类：

package com.stu_computer;

public class MachineRoom {
    //属性
    public Computer[] computer = new Computer[5];
    //方法
    public MachineRoom(){
        init();
    }
    public void init(){
        for(int i=0;i<computer.length;i++){
            computer[i] = new Computer(i+1);
        }
    }
    //欢迎学生进机房的方法
    public void welStudent(Student student){
        System.out.println("欢迎"+student.getName()+"进来机房");
        for(int i=0;i<computer.length;i++){//通过遍历找到未被开机的电脑  供学生使用
            if(!computer[i].isUsed()){
            student.useComputer(computer[i]);
            break;//找到之后即结束查找
            }
        }
    }
    
}

学生类：
package com.stu_computer;

public class Student {

    //学生和电脑是依赖的关系
    //属性
    private String name;
    private int RP = (int)(Math.random()*10);
    //方法
    public String getName() {
        return name;
    }
    //构造方法
    public Student(){}
    public Student(String name){
        this.name = name;
    }
    //学生使用电脑的方法
    public void useComputer(Computer computer){
        System.out.println(this.name+"使用"+computer.getNumber()+"号电脑啦");
        computer.beOn(computer);
        computer.beUsing(computer);
        //判断学生的RP，根据RP情况选择是否执行关机操作
        if(this.RP<5){
            computer.beOff(computer);
        }else{
            System.out.println(this.name+"人品太差了，没关电脑");
        }
    }
}

测试类：
package com.stu_computer;

public class Test {
    public static void main(String[] args) {
        //创建一个机房对象
        MachineRoom machineRoom = new MachineRoom();
        //创建学生对象  机房执行欢迎学生进来的方法
        Student student1 = new Student("小花");
        machineRoom.welStudent(student1);
        Student student2 = new Student("小ff");
        machineRoom.welStudent(student2);
        Student student3 = new Student("小文件");
        machineRoom.welStudent(student3);
    }
    
}

2.测速器测量小汽车速度，警车追击小汽车

package com.car_policecar;

public class Car {
    //属性
    private int speed;
    //方法
    //获取小汽车的速度
    public int getSpeed() {
        return speed;
    }
    //构造方法
    public Car(){}
    public Car(int speed){
        this.speed = speed;
    }
}

package com.car_policecar;

public class PoliceCar {
    //属性
    private int speed;
    //方法
    //获取警车的速度
    public int getSpeed() {
        return speed;
    }
    public PoliceCar(){}
    public PoliceCar(int speed){
        this.speed = speed;
    }
    //追击小汽车方法
    //比较警车和小汽车速度 判断是否能追上
    public void catchCar(Car car){
        if(this.speed>car.getSpeed()){
            int time = 100/(this.speed - car.getSpeed());
            System.out.println("经过"+time+"s追击成功");
        }else{
            System.out.println("追击失败");
        }
    }
    
}

package com.car_policecar;

public class VelometerMachine {
    private int standardTime;
    
    public int getStandardTime() {
        return standardTime;
    }

    //方法
    public VelometerMachine(){}
    public VelometerMachine(int time){
        this.standardTime = time;
    }
    public void measureSpeed(Car car){
        int carSpeed = car.getSpeed();
        int carTime = 100/carSpeed;
        if(this.standardTime>carTime){//小汽车超速了
            System.out.println("小汽车超速，马上进行追击");
            PoliceCar pc = new PoliceCar(25);
            pc.catchCar(car);
        }else{
            System.out.println("小汽车速度正常");
        }
        
    }
}

package com.car_policecar;

public class Test {
    public static void main(String[] args) {
        VelometerMachine vm = new VelometerMachine(5);
        Car car = new Car(26);
        vm.measureSpeed(car);
    }
}