Java Map为当前键返回null

Question

I'm having a very unusual problem.
Basically, I'm trying to get the value associated with a key from a Map of Strings to Strings.
I know that the key I'm using is present; I'm using the same string I used to put it in!

I've print statements all over my code, and this is case I have...
Here is my dictionary characterDictionary

{thusChar=∴, spaceChar= , plusChar=+, equalsIndent=#, multiplyChar=×, equalsChar==, newlineChar=\n, divideChar=÷, subjectChar=:, variableIndent=@}

The very last key "variableIndent" is the trouble!
Here's the code...

System.out.println  (   characterDictionary.get("variableIndent") );

which inappropriately outputs: null

I have checked, double checked and triple checked my code.
There is absolutely no difference between the key "variableIndent" and the string argument of characterDictionary.get("variableIndent") , yet it's behaving as if this key was not present.

I can absolutely guarantee this key is present, and that the two strings are identical.
All the other elements (the ones I've checked; about 3 so far) of the dictionary are retrieved as normal. Why is "variableIndent" with it's "@" value playing up?

You might notice the dictionary contains non ASCII characters, like "thusChar". Could this be related?

Thanks
(This seems like a very simple and trivial problem, as if I've made some pitifully silly mistake, but yet I just can't solve it!)

EDIT:

Okay, this HAS to be something about encoding.
I took the string key from the dictionary and compared it to my get argument.
When printed, they are identical, but java says they are not equal.
The key string came from a UTF-8 encoded text file, whilst the argument string came from a java Eclipse literal.
The characters are identical however.
What is the issue, and how can I resolve it?

Thanks!

EDIT:

Hmmm, here's what's actually happening behind the scenes.
I have a UTF-8 text file which contains the following content...

variableIndent,@
equalsIndent,#
spaceChar, 
newlineChar,\n
multiplyChar,×
divideChar,÷
plusChar,+
equalsChar,=
subjectChar,:
thusChar,∴

I 'load' this file by reading in each line of the file as an ArrayList<String> element, by passing the directory of the file:

private static ArrayList<String> readLinesFile(String ResourceFile)  {
    ArrayList<String> Lines = new ArrayList<String>();
        try{
            InputStream fstream = FileManager.class.getResourceAsStream(ResourceFile);
            BufferedReader br = new BufferedReader(new InputStreamReader(fstream));
            String strLine;
            while ((strLine = br.readLine()) != null)  {
                Lines.add(strLine);  } 
            in.close();  }
        catch (Exception e)  {
            System.out.println("Error: " + e.getMessage());  } 
        return Lines;  }

Everything is fine up to here.
I then pass this ArrayList into a function that splits up each element by the "," character (using a function from a personal package; It is definitely not the issue), and adds the first part as a key to the second in the new dictionary.

private static Map<String, String> generateBaseUnits_Characters_Prefixes(ArrayList<String> FileContent)  {
    Map<String, String> BaseUnitsCache = new HashMap<String, String>();
    ArrayList<String> currentLine;
    for (int i=0; i<FileContent.size(); i++)  {
        currentLine = MiscellaneousFunctions.splitString(FileContent.get(i), ",");
        BaseUnitsCache.put(currentLine.get(0), currentLine.get(1)); }
    return BaseUnitsCache;  }

and this produces the dictionary that is causing all the trouble.
I have a set of Key Literals that correspond to the character names in the text files, which I use to access the dictionary in the program.

public static String variableIndentKey = "variableIndent";
public static String equalsIndentKey = "equalsIndent";
public static String spaceCharKey = "spaceChar";  
public static String newlineCharKey = "newlineChar";
public static String multiplyCharKey = "multiplyChar";
public static String divideCharKey = "divideChar";  
public static String plusCharKey = "plusChar";
public static String equalsCharKey = "equalsChar";  
public static String subjectCharKey = "subjectChar";
public static String thusCharKey = "thusChar";

HERE'S THE PROBLEM:

The top line of the textfile 'screws up' in the dictionary. It is added to the dictionary and appears correctly amongst the keySet and the printed format of the dictionary, but trying to access it returns "null".
(In this case, it's variableIndent. If I put variableIndent somewhere else in the text file, equalsIndent screws up, etc)

What's going on!?
Do I have a dodgy function?!
They've worked well for everything else.

Thanks!

Answer 1

change you UTF-8 text file which contains the key and value to UTF-8 without BOM. There are three bytes(UTF-8 BOM 0xEF,0xBB,0xBF before "variableIndent") see http://en.wikipedia.org/wiki/Byte_order_mark

Answer 2

If you are afraid of encoding issues (that seems to be the problem here), you have to make sure your project's encoding is set to UTF-8 . To check it, go to Project menu, and choose Properties . It may be required to change text file encoding from Inherited from container to Oher: UTF-8

Answer 3

I suggest you look at your code in a debugger. I suspect the map is not what you think it is.

String data = "{thusChar=∴, spaceChar= , plusChar=+, equalsIndent=#, multiplyChar=×, equalsChar==, newlineChar=\\n, divideChar=÷, subjectChar=:, variableIndent=@}";
Map<String, String> map = new LinkedHashMap<String, String>();
for (String keyValue : data.substring(1, data.length() - 1).split(", ")) {
    String[] parts = keyValue.split("=", 2);
    map.put(parts[0], parts[1]);
}
System.out.println("variableIndent is " + map.get("variableIndent"));

prints

variableIndent is @

---

can you try

for(String key: map.keySet())
   System.out.println("'"+key+"'= "+map.get(key));

Answer 4

Hmm try this code and let us know the output

for (String key : characterDictionary.keySet() ) {
System.out.println(key);
}

for ( String value :  characterDictionary.values() ) {
System.out.println(value);
}

PS: Might want to change Type of key and value.

Answer 5

If you think it's an encoding issue, then try using the following methods to compare the actual content, irrespective of what it looks like.

Use getBytes() to get all the bytes from both Strings (the key from the map, as well as the string in your code), and print

1. The length of the byte array
2. Each byte as an integer

Then use getChars() to get all the chars from both Strings or charAt() to read each char, and print

1. Each char as an integer.

Between these two checks you should be able to figure out how both strings are different at a byte level. What's the character-set that the file is saved in?

EDIT

I suspect your use of DataInputStream is causing problems with the bytes being read.

InputStream fstream = FileManager.class.getResourceAsStream(ResourceFile);
DataInputStream in = new DataInputStream(fstream);
BufferedReader br = new BufferedReader(new InputStreamReader(in));

The Java docs for DataInputStream say "A data input stream lets an application read primitive Java data types from an underlying input stream in a machine-independent way. An application uses a data output stream to write data that can later be read by a data input stream." You're not reading from a DataOutputStream here, just a regular file. Also, you already have an InputStream for the InputStreamReader to use. Change your code to this:

InputStream fstream = FileManager.class.getResourceAsStream(ResourceFile);
BufferedReader br = new BufferedReader(new InputStreamReader(fstream));

EDIT 2

Another thing worth doing, since your string from the text file is 3 bytes longer, is changing this

BaseUnitsCache.put(currentLine.get(0), currentLine.get(1));

to

BaseUnitsCache.put(currentLine.get(0).trim(), currentLine.get(1).trim());

Answer 6

Try it this way...

Map<String, String> map = new LinkedHashMap<String, String>();


for (Map.Entry<String, String> mp : map.entrySet()){


  System.out.println("Key: "+mp.key()+"::"+"Value: "+mp.value());


}