BitSet and Byte Array value getting SET from opposite direction

Question

I have:

public byte[] bytes = new byte[5];     //BitComp Class
public BitSet bits = new BitSet(40);

and the getters and setters in class named BitComp. The following class sets all the first 8 bits to 1(byte[0]).After that it converts all bytes to BitSet. Now after that when it sets the 2nd bit to true and prints both of them.

import java.util.BitSet;
public class TestBitSet {

    public void testBit(){

        BitComp comp = new BitComp();       

        comp.bytes[0] |= 0xFF;

        comp.setBits(getBitsFromByte(comp.getBytes()));

        System.out.println(toCharArray(comp.getBits()));

        BitSet bs = comp.getBits();
        bs.set(1,true);

        comp.setBits(bs);

        System.out.println(toCharArray(comp.getBits()));    
    }

     private BitSet getBitsFromByte(byte[] barray) 
        {
            BitSet bits=new BitSet();
            if(barray!=null)
            {
                for (int i=0; i<barray.length*8; i++) 
                {
                    if ((barray[barray.length-i/8-1]&(1<<(i%8)))!= 0) 
                    {
                        bits.set(i);
                    }
                }
            }
            return bits;
        }

     public static char[] toCharArray(final BitSet bs)
        {     
           final int length = bs.length();     
           final char[] arr = new char[length];     
           for(int i = 0; i < length; i++)
           {         
             arr[i] = bs.get(i) ? '1' : '0';     
           }  
          return arr; 
        }

    public static void main(String args[]){
        TestBitSet tbs = new TestBitSet();
        tbs.testBit();
    }

}

Output:0000000000000000000000000000000011111111 <- 0th
0th-> 0100000000000000000000000000000011111111

There should not ne any change cause byte[0] contains the first 8 elements and I am setting the 2nd element as 1 with BitSet operation. So BitSet is approaching from LHS and Byte array is stored from RHS. How to approach this problem? Is there a problem in getBitsFromByte method? Please Suggest. Thanks

The 0th,1st bit for byte array is the 78th and 79 th bit for BitSet class.. Y is that? — JavaBits

Peter Lawrey Peter Lawrey · Accepted Answer · 2011-06-01T15:38:52

You don't provide the code for BitComp, however it appears to me that you determine how to translate bits into bytes and what order to print the bytes.

Its entirely up to you what order you what things to be set or printed out.

BitSet and Byte Array value getting SET from opposite direction

2 Answers