这个比较器如何工作？ [英] How does this comparator work?

问题描述

  package vehicles_order; 
 
 import java.util.ArrayList; 
 import java.util.Collections; 
 import java.util.Iterator; 
 
公共类车辆实现类似{
 
 String Vehicle; 
 String Make; 
字符串类型; 
 double Cost; 
 
 
 public static void main（String [] args）{
 
 ArrayList cars = new ArrayList（）; 
 cars.add（新车（CAR，Peugot，3008，12500.00））; 
 cars.add（新车（CAR，BMW，316，4995.00））; 
 cars.add（新车（CAR，Ford，Fiesta，2995.00））; 
 
 Collections.sort（cars）; 
迭代器itr = cars.iterator（）; 
 
 while（itr.hasNext（））{
 Object element = itr.next（）; 
 System.out.println（element +\\\
）; 
} 
} 
 
公共车辆（String vehicle，String make，String type，double cost）{
 Vehicle = 
 Make = make; 
 Type = type; 
 Cost = cost; 
} 
 
 public String toString（）{
 returnVehicle：+ Vehicle +\\\
+Make：+ Make +\\\
 类型：+类型+\\\
+成本：+成本; 
} 
 
 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; 
} 
} 
  

我的比较器在底部，我只是想知道它实际上工作。假设它像一个堆栈，当它返回1它向上移动堆栈，如果其-1向下移动。

此外，任何人都可以告诉我如何id去排序汽车通过不同的方法。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。

解决方案

什么是一个比较接口？它是一个包含单一方法的接口：

  compareTo（T o）
  pre> 
 
 
提供Java与其他任何对象进行对比的能力。基本上你想比较你的对象与同一类（类）。因此，通常在 compareTo 实现中检查：
  if（o instanceof vehicles）{
 Vehicles v =（Vehicles）o; 
 
 //比较
} else {
 return false; 
} 
  
然后，在比较部分，您应该根据您的业务规则， 
 
 
 
 
 
 0  - 如果它们相等; 
 
 
 1  - 如果您的对象更大; 
 
 
 -1  - 如果您的对象较小。
 
 
 
 $ b b 
这么简单！
 
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;
}
}
My comparator is at the bottom and I just wondering how it actually works. Im guessing its like a stack, where when it returns 1 it moves up the stack if its -1 moves down.

Also, can anyone tell me how id go about ordering the cars via a different method. For example, store the cost in a temp highest value and check if the new value is higher than the current one
解决方案
What is a Comparable interface? It is an interface containing single method:
compareTo(T o)
providing capability for Java to comprare your object with any other. Basically you would like to compare your object with those of the same kind (class). So there is a usual check in compareTo implementation:
if (o instanceof vehicles) {
  Vehicles v = (Vehicles)o;

  // compare
} else {
  return false;
}
Then, in compare section you should decide, based on your business-rules, whether other vehicle is equals, more of less to your object.


0 - if they are equal;
1 - if your object is greater;
-1 - if your object is lesser.


All that simple!

                        
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