Java Map匹配密钥

Question

i am facing a problem which is: I have map containing string and string. When i print that map i can see that there is a key "0-8166-3835-7". But when i am trying to get it, there is nothing to get returned, like no matching found... My code:

    //Open a stream to read from file with isbn's AND titles
    Scanner IsbnTitle = new Scanner(new FileReader("C:/Users/Proskopos/Documents/NetBeansProjects/ReadUrl/IsbnTitle.txt"));

    //Create a Map to save both ISBN's and Titles
    Map <String,String> IsbnTitleMap = new HashMap();

    while(IsbnTitle.hasNext()){
        String recordIsbnTitle = IsbnTitle.nextLine();
        UrlFunctions.AddToMap(Recognised , recordIsbnTitle, IsbnTitleMap);
    }
.....
.....
        Set IsbnSet = new HashSet();
    while (IsbnFile.hasNextLine()) {
        String isbn = IsbnFile.nextLine();
        IsbnSet.add(isbn);
    }

    //Create an Iterator for IsbnSet
    Iterator IsbnIt =IsbnSet.iterator();

String suffix = IsbnIt.next().toString();

    String OPACIALtitle = UrlFunctions.GetOpacTitle(suffix, IsbnTitleMap);

The code above is the only part in main about MAP and below are the functions i call:

    static String GetOpacTitle(String opIsbn, Map IsbnTitle) {
    String OpacTitle = null;
    String isbn = opIsbn;
    Map isbnMap = IsbnTitle;
    System.out.println(isbn);
    if ( isbnMap.containsKey(isbn)){
        System.out.println("AAAAAAAAAAAAAAAA");
    }
    //String tade = isbnMap.get(isbn).toString();
    //System.out.println("*************" + tade);

    return OpacTitle;
}


    static void AddToMap(int Recognise, String recordIsbnfollowed, Map IsbnfollowedMap) {

    Map isbnsth = IsbnfollowedMap;
    String records = recordIsbnfollowed;
    int recs= Recognise;


    if (recs == 0 || recs == 3) {
    String isbn = records.substring(0, 10);
    String title = records.substring(10);
    isbnsth.put(isbn, title);
//        System.out.println(isbn);
        }else if (recs == 1) {
            String isbn = records.substring(0, 14);
            String title = records.substring(14);
            isbnsth.put(isbn, title);
//            System.out.println(isbn);
        }
    }

I cant understand where the problem is.. Maybe it is something like encoding of the suffix cames from a set, and the key from a map? they are both string.. dont think so..!!! So? Can you help?

EDIT: I am trully sorry if you find the code difficult to read :\\ I will follow your advices!! BUT in case that anyone else has the same problem the solution was what Brand said below.. (I re-post it)

You probably have some whitespace in the Strings that you are reading form the file and storing in the Map. If this is the case use String.trim() before storing the value in the Map, and also before querying for the same string. – Brad 3 hours ago

Thank you all

Answer 1

Just to add to my comment that identified the problem. When comparing Keys in a Map you must be very careful about white space and case sensitivity. These types of issues commonly occure when reading data from Files because it's not always obvious what characters are being read. Even looking in your debugger whitepsace cna be an issue.

Always try to "normalize" your data by trimming leading and trailing whitespace before storing it in a Map.