Question

1.我试图按标题按字母顺序对歌曲列表进行排序，但所有发生的事情都是列表按相反顺序排列然后输出。

public void sort()
{
  //create a pointer to hold the temp for switching
  MusicHW02 temp;

  //two nested loops. Go through entire list less 1 
  for (int index = 0;index< count -1;index++) {

    /*inner for loop to go through list starting with next index 
     *to see if smaller 
     */
    for(int index2= index +1; index2<count; index2++) {

      //Sort method to compare Strings
      if(collection[index2].getTitle().compareTo(collection[index].getTitle())<0);{
        temp = collection[index2];
        collection[index2] = collection[index]; 
        collection[index] = temp;
      }//END OF IF STATEMENT
    }//END OF INNER FOR LOOP
  }//END OF OUTER FOR LOOP
}//END OF SORT METHOD

Answer 1

删除if语句末尾的分号，因为它将被视为n空语句

if(collection[index2].getTitle().compareTo(collection[index].getTitle())<0);{}

到

if(collection[index2].getTitle().compareTo(collection[index].getTitle())<0){}

为什么不使用

Collections.sort(someList);

或

Arrays.sort(someArray);

或类似的东西

String arr[] ={"abc","def","adf","acb"};
Collections.sort(Arrays.asList(arr),new Comparator<String>() {
    @Override
    public int compare(String o1, String o2) {
        return o1.compareTo(o2);
    }
});
System.out.println(Arrays.toString(arr));

Answer 2

您应该使用比较器。这将使您可以根据需要灵活地进行排序。我把它扔在一起，但它应该帮助你做你想要的。这确实是泡泡排序顺便说一下。使用比较器，您还可以在排序之前将它们转换为所有大写/小写，这样即使字符串大小写不匹配，您也总是按正确的顺序排列它们。

Coparator<String> songComparator = new Comparator<String>() {
   public int compare(String str1, String str2) {
      if (str1 == null) {
         return 0;
      }
      return (str2 != null) ? str1.compareTo(str2) : 1;

   }

}

Arrays.sort(<collection you want to sort>, songComparator);

以下是一个很好的示例列表http://www.mkyong.com/java/java-object-sorting-example-comparable-and-comparator/

如何按字母顺序对此列表进行排序，需要帮助

2 个答案: