Not sure how to do this while loop

Question

Here is my code:

public static void decodeThis(BufferedImage im, String outputFile)
throws FileNotFoundException{
  int w = im.getWidth();
  int h=im.getHeight();
  int[] arr=im.getRGB(0, 0, w, h, null, 0, w);
  int[] eightBit=new int[8];
  int counter=0;
  String[] aString=new String[arr.length];
  PrintStream out=new PrintStream(new File(outputFile));
  double value=0;
  int intVal=0;
  while (counter<arr.length){
    for (int j=0;j<eightBit.length;j++){
        eightBit[j] = arr[j+counter] & 1; //Extracts least significant bit, puts into eightBit array.
    }
    value=0;
    for (int x=0;x<eightBit.length;x++){
        value+=eightBit[x]*(Math.pow(2,x));
    }
    intVal=(int)value;
    out.print((char)intVal);
    counter=counter+8;
}

}

What I want to do is read, extract, and convert into a character 8 bits from arr while there are still pixels left to read in arr. For some reason when I run the commented for loop, I get an ArrayIndexOutOfBoundsException. How do I fix this? Thanks in advance!

Answer 1

The while(counter<arr.length) loop runs counter to the length of arr , and the inner loop accesses arr using j+counter ; that's guaranteed to run off the end of arr if arr is not an exact multiple of 8.

And since arr is the number of bits in the image, it's highly unlikely to be an exact multiple of 8.

Answer 2

更改循环条件。

while (counter <= arr.length - 8)