这个比较器如何工作？

Question

package vehicles_order;

import java.util.ArrayList;
import java.util.Collections;
import java.util.Iterator;

public class vehicles implements Comparable  {

    String Vehicle;
    String Make;
    String Type;
    double Cost;


public static void main(String[] args){

    ArrayList cars = new ArrayList();
    cars.add(new vehicles ("CAR","Peugot","3008",12500.00));
    cars.add(new vehicles ("CAR","BMW","316",4995.00));
    cars.add(new vehicles ("CAR","Ford","Fiesta",2995.00));

    Collections.sort(cars);
    Iterator itr = cars.iterator();

    while(itr.hasNext()){
        Object element = itr.next();
        System.out.println(element + "\n");
    }
}

public vehicles(String vehicle, String make, String type, double cost){
    Vehicle = vehicle;
    Make = make;
    Type = type;
    Cost = cost;
}

public String toString() {
    return "Vehicle: " + Vehicle + "\n" + "Make: " + Make + "\n" + "Type: " + Type + "\n" + "Cost: " + Cost;    
}

public int compareTo(Object o1) {
    if (this.Cost == ((vehicles) o1).Cost)
        return 0;
    else if ((this.Cost) > ((vehicles) o1).Cost)
        return 1;
    else
        return -1;
}
}

我的比较器位于底部,我只是想知道它是如何工作的.我猜它就像一个堆栈,当它返回1时,如果它向下移动,它会向上移动堆栈.

此外,任何人都可以告诉我如何通过不同的方法订购汽车.例如,将成本存储在临时最高值中,并检查新值是否高于当前值

Answer 1

什么是可比较的界面？它是一个包含单个方法的接口:

compareTo(T o)

为Java提供与任何其他对象进行比较的能力.基本上你想将你的对象与同类(对象)的对象进行比较.所以在compareTo实现中有一个常见的检查:

if (o instanceof vehicles) {
  Vehicles v = (Vehicles)o;

  // compare
} else {
  return false;
}

然后,在比较部分,您应该根据您的业务规则决定其他车辆是否等于,对您的对象更少.

• 0 - 如果他们是平等的;
• 1 - 如果你的对象更大;
• -1 - 如果您的对象较小.

就这么简单!