排序功能-如何改进

Question

我有以下排序代码。这还能改进吗？

import java.util.*;
class Church {
    private String name;
    private String pastor;
    public Church(String name, String pastor) {
        this.name = name;
        this.pastor = pastor;
    }
    public String getPastor() {
        return pastor;
    }
    public String getName() {
        return name;
    }
    public void setPastor(String pastor) {
        this.pastor = pastor;
    }
    public String toString() {
        return getName() + " is Pastored by "+getPastor();
    }
    public int compareByPastor(Church c) {
        int x = pastor.compareTo(c.getPastor());
        return x;
    }
    public int compareByName(Church c) {
        int x = name.compareTo(c.getName());
        return x;
    }
}

class Churches {
    private final List<Church> churches;

    public Churches() {
        churches = new ArrayList<Church>();
    }
    public void addWithoutSorting(Church c) {
        churches.add(c);
    }

    //You could always add using this method
    public void addWithSorting(Church c) {

    }
    public void display() {
        for(int j = 0; j < churches.size(); j++) {
            System.out.print(churches.get(j).toString());
            System.out.println("");
        }
   }
   public List<Church> getChurches() {
       return churches;
   }
   public void sortBy(String s) {
       for (int i = 1; i < churches.size(); i++) {
           int j;
           Church val = churches.get(i);
           for (j = i-1; j > -1; j--) {
               Church temp = churches.get(j);
               if(s.equals("Pastor")) {
                   if (temp.compareByPastor(val) <= 0) {
                       break;
                   }
               }
               else if(s.equals("Name")) {
                   if (temp.compareByName(val) <= 0) {
                          break;
                   }
               }
               churches.set(j+1, temp);
            }
            churches.set(j+1, val);
       }
     }

    public static void main(String[] args) {
        Churches baptists = new Churches();
        baptists.addWithoutSorting(new Church("Pac", "Pastor G"));
        baptists.addWithoutSorting(new Church("New Life", "Tudor"));
        baptists.addWithoutSorting(new Church("My Church", "r035198x"));
        baptists.addWithoutSorting(new Church("AFM", "Cathy"));
        System.out.println("**********************Before Sorting***********************");
        baptists.display();
        baptists.sortBy("Pastor");
        System.out.println("**********************After sorting by Pastor**************");
        baptists.display();
        baptists.sortBy("Name");
        System.out.println("**********************After sorting by Name****************");
        baptists.display();

    }

  }

Answer 1

看看Collections.sort(列表，比较器) http://download.oracle.com/javase/6/docs/api/java/util/Collections.html

Answer 2

class Churches
{
    public void sortBy(String attribute) 
    {
      Comparator<Church> c = null;

      if ("Name".equals(attribute)) c = new ChurchNameComparator();
      else if ("Pastor".equals(attribute)) c = new ChurchNameComparator();
      else System.out.println("unexpected sort attribute : '" + attribute + "'");

      if (c != null) Collections.sort(churches, c);
    }

    private static final class ChurchNameComparator implements Comparator<Church> 
    {
      public int compare(Church c1, Church c2)
      {
        return c1.getName().compareTo(c2.getName());
      }
    }

    private static final class ChurchPastorComparator implements Comparator<Church> 
    {
      public int compare(Church c1, Church c2)
      {
        return c1.getPastor().compareTo(c2.getPastor());
      }
    }
}

Answer 3

这里的实际答案与iluxa的非常一致:您希望在您的教堂对象上实现一个比较器接口(示例代码here，尽管您可能希望确定教堂的大于/小于……)，然后可以使用Collections.sort()对它们进行排序。这将在一天结束的时候完成这项工作。

当然，您刚刚询问了关于Stack Overflow排序的建议，所以我觉得有必要问您是否需要就地排序，您希望获得什么样的大O性能，然后让您在Quicksort、IntroSort、HeapSort、MergeSort和StoogeSort中选择最适合您的。

为了提高效率，我曾经用Java编写了一些排序：

• This one强制将快速排序转换为二次时间，这比我最初假设的更难，
• 这篇文章展示了如何实现MergeSort，
• ，这篇文章演示了一个HeapSort

我这样做是为了我自己的乐趣和教育。一般来说，对于这类事情，您应该坚持使用标准库。