Question

所以这是我的代码。当我运行测试时，它会给出索引超出范围的错误并高亮显示if

(songList.get(j).getDuration()<(songList.get(j-1).getDuration())  )
        {

部分代码。我该如何解决？？？ import java.util.ArrayList;

/**
 * Write a description of class SongList here.
 * 
 * @author (your name) 
 * @version (a version number or a date)
 */
public class SongList
{

  private ArrayList <Song> songList;
/**
     * Constructor for objects of class SongList
     */
    public SongList()
    {
     songList = new ArrayList<Song>();

}

public boolean addSong(Song s)

        {

         songList.add(s);

         return true;   
        }

    public int findSong(String title)
    {
      for  (int i=0; i < songList.size(); ++i)
       {
       if ( songList.get(i).getTitle().compareTo(title) == 0)
       return i;
    }
    return -1 ; 


}

public  void swapSong(int i, int j)
    {

        Song[  ] ai = new Song [100];
        Song temp = ai[i];
        ai[i] = ai[j];
        ai[j] = temp;    
    }


public void sortByDuration()
{
for(int i=0; i < songList.size()-1; ++i)
    {
        for (int j = songList.size()-1; j > i ; ++j)
    {
         if (songList.get(j).getDuration()<(songList.get(j-1).getDuration())  )
        {

            swapSong(j,j-1);

        }


    }   

}


}


public void sortByWriter()
{
 for(int i=0; i < songList.size()-1; ++i)
    {
        for (int j = songList.size()-1; j > i ; --j)
    {
  if( songList.get(j).getWriter().compareTo(songList.get(j-i).getWriter())<0)
  {


  swapSong(j,j-1);

}
}
}
}



public void sortByGenre()
{
    for(int i=0; i < songList.size()-1; ++i)
    {
        for (int j = songList.size()-1; j > i ; --j)
    {
  if (songList.get(j).getGenre().compareTo(songList.get(j-1).getGenre())<0)
  swapSong(j,j-1);
}
}}



public  void sortByYear()
{
    for(int i=0; i < songList.size()-1; ++i)
    {
        for (int j = songList.size()-1; j > i ; --j)
    {
if (songList.get(j).getYear()<(songList.get(j-1).getYear()))
swapSong(j,j-1);

}
}}


public int getSize()
{
    return songList.size();

}
}

Answer 1

您尝试使用ArrayList j循环在for的末尾开始。

for (int j = songList.size()-1; j > i ; ++j)

但是，这会增加j，因此您会跑到ArrayList的末尾。

相反减少了j，所以你不会跑到最后，所以循环最终会j遇到i并终止：

//                                      HERE
for (int j = songList.size()-1; j > i ; --j)

您的其他j for循环已正确--j。

需要有关arraylist上的Index out of bounds exception的帮助

1 个答案: