Base64无法将字符串解码为字节数组

Question

I tried to decode a string to byte array using Base64 . But it returned null . Here is the code:

    LZW lzw = new LZW();
    String enkripEmbedFileString = Base64.encode(byteFile);
    List<Short> compressed = lzw.compress(enkripEmbedFileString);

    String kompress = "";
    Iterator<Short> compressIterator = compressed.iterator();
    while (compressIterator.hasNext()) {
        String sch = compressIterator.next().toString();
        int in = Integer.parseInt(sch);
        char ch = (char) in;
        kompress = kompress + ch;
    }

    byteFile = Base64.decode(kompress);

I call "byteFile" variable at the last row in a code below this code and it throw NullPointerException . I have check the "kompress" variable and it's not null. It contains a string .

All you need to know is, with that code I compress a string with LZW which require String for parameter and returns List<Short> . And, I convert the List<Short> to a String with a loop that you can see.

The problem is, why Base64 failed to convert String to byte[] , after that String modified with LZW?

Whereas, if I decompress the String first and than return the decompressed String to be converted with Base64 to byte[], has no problem. It works. Here is the code which works:

    //LZW Compress      
    LZW lzw = new LZW();
    String enkripEmbedFileString = Base64.encode(byteFile);
    List<Short> compressed = lzw.compress(enkripEmbedFileString);

    String kompress = "";
    Iterator<Short> compressIterator = compressed.iterator();
    while (compressIterator.hasNext()) {
        String sch = compressIterator.next().toString();
        int in = Integer.parseInt(sch);
        char ch = (char) in;
        kompress = kompress + ch;
    }

    //Decompress        
    List<Short> kompressback = back(kompress);
    String decompressed = decompress(kompressback);

    byteFile = Base64.decode(decompressed);

Please, give me an explanation. Where is my fault?

Answer 1

Base64 decode can be applied only to strings that contain Base64 encoded data. Since you encode and then compress, the result is not Base64. You proved it yourself when you saw that uncompressing the data first allowed you to then decode the Base64 string.