爲什麼Collections.binarySearch不能一致地輸出

Question

所以我想爲學校編寫一個程序。它的要點是要製作用戶在其收藏中的CD列表。該程序需要以原始順序（CDS）和按字母排序順序（CDSS）顯示CD列表。信息必須存儲在數組列表中。我也必須使用它能夠添加和刪除程序。

當我輸入歌曲「Beatles - Abbey Road」時，我認爲它會從collections.binarySearch輸出1，但是它會輸出-1兩次然後輸出1。它似乎適用於其他歌曲。

，因爲它創建了一個錯誤

感謝您的幫助

private void buttonInitializeActionPerformed(java.awt.event.ActionEvent evt) {             
    //this is where the original songs are added(when the initialize button is pressed) 
    Collections.addAll(CDS, "Metric - Fantasies", "Beatles - Abbey Road", "Pearl Jam - Ten", "Doors - Alive", "The Rolling Stones - Gimme Shelter"); 
    Collections.addAll(CDSS, "Metric - Fantasies", "Beatles - Abbey Road", "Pearl Jam - Ten", "Doors - Alive", "The Rolling Stones - Gimme Shelter"); 
    //once the initialize button is pressed the other buttong will be able to be enabled 
    buttonDisplay.setEnabled(true); 
    buttonRemove.setEnabled(true); 
    buttonAdd.setEnabled(true); 
    buttonInitialize.setEnabled(false); 
}             

private void buttonDisplayActionPerformed(java.awt.event.ActionEvent evt) {            
    outputSongList.setText("Original Order"); 

    int condition = 0; 
    //condition is the value thatis increased by 1 every time each of these while loops are ran. 
    //from 1 to however many objects there are in the either the CDS or CDSS array list 
    //the extra S in CDSS stands for sorted 
    while(condition < CDS.size()){ 
     outputSongList.setText(outputSongList.getText() + "\n" + CDS.get(condition));//writing the contents of the array list to the text area 
     condition++; 
    } 
    outputSongList.setText(outputSongList.getText() + "\n\n\nSorted Order"); 

    Collections.sort(CDSS, String.CASE_INSENSITIVE_ORDER);//this sorts the CDSS array in alphabetical order 

    condition = 0; 

    while(condition < CDSS.size()){ 
     outputSongList.setText(outputSongList.getText() + "\n" + CDSS.get(condition));//the same as the previous while loop 
     condition++; 
    } 
    buttonDisplay.setEnabled(false);//disables the display button so the user knows that all information is displayed 
}            

private void buttonAddActionPerformed(java.awt.event.ActionEvent evt) {           
    String inputSong = enterSong.getText();//getting the string that the user typed into the enterSong text field 

    if(Collections.binarySearch(CDS, inputSong) < 0){//this checks if the inputted song is in the arraylist 
     CDS.add(inputSong);        //if it is, the outputted number will be 1...i thought 
     CDSS.add(inputSong);       //if it isn't the numer will be less than 0 
     Collections.sort(CDSS);    //this if statement will run if the inputted song isn't already in the arrays 
     buttonDisplay.setEnabled(true);     
    } 
}           

private void buttonRemoveActionPerformed(java.awt.event.ActionEvent evt) {            
    String inputSong = enterSong.getText(); 

    if(Collections.binarySearch(CDS, inputSong) > -1){//if the inputted song is in the array this line will run 
     CDS.remove(Collections.binarySearch(CDS, inputSong)); 
     CDSS.remove(Collections.binarySearch(CDS, inputSong)); 
     buttonRemove.setEnabled(false); 
     buttonDisplay.setEnabled(true); 
    } 
} 

Answer 1

從你說什麼，我也不能刪除歌曲，CDS不以任何特定的順序排序。 Collections.binarySearch在它的Javadoc中清楚地表明它只在收到的列表已經排序時才起作用。

而不是使用Collections.binarySearch，您將不得不使用​​並接受線性搜索。