读取文件中的字节：java.lang.NegativeArraySizeException

Question

I have gone through the similar posts but none of them really answered my question. Hence I post my question in a separate thread. I need to skip some bytes in the file which I am reading in the byte array.I am trying to achieve this through code below

 1. byte [] readBytesToSKip = null;
 2. readBytesToSKip = new byte[(int)bytesToSkip];
 3. bytesReadToSkip = System.in.read(readBytesToSKip) ;
 4. if(bytesReadToSkip > 0)
 5. {
 6.      baos_.write(readBytesToSKip, 0, bytesReadToSkip);   
 7. }

But I get a NegativeArraySizeException at line 2 where the size exceeds Integer.MAX_VALUE . I am not sure how to achieve this otherwise.

bytesToSkip is long as I calculate in function below:

public static long bytesToLong1(byte[] bytes) {
        long value = 0;
        for (int i = 0; i < bytes.length; i++)
        {
           value = (value << 8) + (bytes[i] & 0xff);
        }
        return value;
    }

Answer 1

Starting from your posted bytes->long function

public static long bytesToLong1(byte[] bytes) {
    long value = 0;
    for (int i = 0; i < bytes.length; i++)
    {
       value = (value << 8) + (bytes[i] & 0xff);
    }
    return value;
}

Whenever bytes.length==8 and the first byte is >= 128 in absolute value (in Java specific: it's a negative byte value), you'll end having a negative value for your long.

Example:

byte vals[]={0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF};

System.out.println(bytesToLong1(vals));

will result it -1 being printed. Which will convert quite fine to an int with a -1 value, but will still be improper for the length of an array.