Java中与ASCII等效的二进制整数数组

Question

I searched around here for awhile and nothing seems to help me with my assignment. I'm trying to convert an int array that has binary code in it manually, do the decimal conversion and then cast it as a char to get the ascii equivalent. I have something started, but when I print it out, I get -591207182 as the message, which obviously isn't correct. I have my program down below. I'm fairly novice at writing and understanding Java, so the most efficient and easy to understand route would be much appreciated.

class DecodeMessage
{
    public void getBinary(Picture secretImage)
    {
    Pixel pixelObject = null;
    Color pixelColor = null;
    int [] binaryInt = new int[secretImage.getWidth()];
    int x = 0;


      int redValue = 0;
        while(redValue < 2)
        {         
            Pixel pixelTarget = new Pixel(secretImage,x,0);
            pixelColor = pixelTarget.getColor();
            redValue = pixelColor.getRed();
            binaryInt[x] = redValue;
            x++;
        }
    }
        public void decodeBinary(int [] binary)
        {
        int binaryLen = binary.length;
        long totVal = 0;
        int newVal = 0;
        int bitVal = 0;
        long preVal = 0;
        long base = 2;

        for(int x = binaryLen - 1; x >= 0; x--)
        {
            bitVal = binary[x];
            preVal = bitVal * base;
            totVal += preVal;
            base = base * 2;
        }

        System.out.println(totVal);
     }
}
public class DecodeMessageTester
{
    public static void main(String[] args)
    {
        Picture pictureObj = new Picture("SecretMessage.bmp");
        pictureObj.explore();
        DecodeMessage decode = new DecodeMessage();
        decode.getBinary(pictureObj);
        int[] bitArray = {0,1,1,0,0,0,1,0,0,1,1,0,1,0,0,1,0,1,1,0,1,1,1,0,0,1,1,0,0,0,0,1,0,1,1,1,0,0,1,0,0,1,1,1,1,0,0,1};
        decode.decodeBinary(bitArray);
    }
}

Answer 1

Your problem is that you're trying to squeeze all 48 bits into one int . However, as http://docs.oracle.com/javase/tutorial/java/nutsandbolts/datatypes.html states, an int in Java can only hold 32 bits, so your numbers overflow. Try changing base , preVal and totVal to long , which can hold 64 bits.

Of course, if you need more than 64 bits (or 63 actually because the last bit is the sign bit), you will not be able to use a primitive number datatype to hold that.