java - 特许经营类的compareTo方法

Question

关闭。此题需要 details or clarity 。目前不接受答案。

---

想要改进这个问题吗？通过 editing this post 添加详细信息并澄清问题.

已关闭 9 年前。

Improve this question

package prob1;

public class Franchise implements Comparable<Franchise> {
    private String location;
    private double totals = 0;
    private String owner;

    public Franchise(String location,double totals,String owner){
        this.location = location;
        this.totals = totals;
        this.owner = owner;
    }
    public String getLocation(){
        return location;
    }
    public double getTotal(){
        return totals;
    }
    public String getOwner(){
        return owner;
    }
    public int compareTo(Franchise that) {
        int stateComparition = this.getLocation().compareTo(that.getLocation()); 
        Double sales = Double.valueOf(this.getTotal());    
        Double thatSales = Double.valueOf(that.getTotal());
        int salesComparition = sales.compareTo(thatSales);    

        if(stateComparition == 0){
            if(salesComparition > 0)
                 return -1;
            else if(salesComparition < 0)
                 return 1;
            else
                 return 0;
        }
           return stateComparition;         
    }

    public String toString(){
        String result = "";
        result = "Owner =  " + getOwner() + " ,State = "+ getLocation() + " ,Sales = " + getTotal() + "\n";

        return result;
    }

}

这个类有一个compareTo方法。我想知道你们能否详细解释一下这个方法是做什么的...基本上我需要你们跟踪它并一步一步地解释我。非常感谢!

package prob1;
import java.util.ArrayList;
import java.util.Collections;

public class FracnahiseTester {

    /**
     * @param args
     */
    public static void main(String[] args) {
         ArrayList<Franchise> franchises = new ArrayList<Franchise>();

         Franchise franchaise1 = new Franchise("CA",3300,"Corey");
         Franchise franchaise2 = new Franchise("GA",1000,"Pato");
         Franchise franchaise4 = new Franchise("NC",3300,"Travis");
         Franchise franchaise3 = new Franchise("NC",3500,"Roy");

         franchises.add(franchaise1);
         franchises.add(franchaise2);
         franchises.add(franchaise4);
         franchises.add(franchaise3);

         Collections.sort(franchises);
         for(Franchise i : franchises){
             System.out.println(i);
         }
    }

}

这是我的测试仪

Answer 1

尽管您可以从 javadoc 获取此信息，这个答案将有助于访问这里的其他用户理解compareTo()方法的概念。

当您实现Comparable接口(interface)时，您的compareTo()方法用于比较不同的对象，

public int compareTo(Franchise that) {
    int stateComparition = this.getLocation().compareTo(that.getLocation()); 
    Double sales = Double.valueOf(this.getTotal());    
    Double thatSales = Double.valueOf(that.getTotal());
    int salesComparition = sales.compareTo(thatSales);    

    if(stateComparition == 0){
        if(salesComparition > 0)
             return -1;
        else if(salesComparition < 0)
             return 1;
        else
             return 0;
    }
       return stateComparition;         
}

• public intcompareTo() 用于将作为参数传递的对象与调用此方法的对象进行比较。
• 如果this对象小于that对象，则返回负整数，在您的情况下为-1。这意味着 this 对象以排序方式排在 that 之前。
• 如果 this 等于 that 对象，则 0 应该相等，这意味着对象相等。
• 如果 this 大于 that 对象，则返回一个正整数，在您的情况下，它是 1。这意味着当对Franchise类型的对象进行排序时，this出现在that之后。