CODEWITHSUNDEEP
java
Jeevan Roy dsouza
Jeevan Roy dsouza

Reputation: 673

Bitwise not operation on a string of bits

I have a string with the value 0111000000. How can I perform a bitwise not operation on this string?

If I convert it to an integer, use the ~ operator and convert it back to a binary string, the resulting string has extra bits. I want the output to be exactly 1000111111.

The following code works fine, but it's not a good method. Is there another better way of doing this?

   String bstr="";
   while(m!=str.length())
   {             
        char a=str.charAt(m);
        if(a=='1')
        {
             a='0';
             bstr=bstr+a;
             m++;   
        }
        else
        {
             a='1'; 
             bstr=bstr+a;
             m++;
         }
}

Upvotes: 3

Views: 2318

Answers (6)

Ronak Jain
Ronak Jain

Reputation: 2440

You can do this using XOR operation

public String xorOperation(String value) {
    String str1 = value;
    long l = Long.parseLong(str1, 2);
    String str2 = "";
    for (int i = 0; i < str1.length(); i++) {
        str2 = str2 + "1";
    }
    long n = Long.parseLong(str2, 2);
    long num = l ^ n;
    String bininaryString = Long.toBinaryString(num);
    System.out.println(bininaryString);
    return bininaryString;
}

Upvotes: 1

Evgeniy Dorofeev
Evgeniy Dorofeev

Reputation: 136152

try this

    char[] a = s.toCharArray();
    for(int i = 0; i < a.length; i++) {
        a[i] = a[i]=='0' ? '1' : '0';
    }
    s = new String(a);

this also works fine

    int i = ~Integer.parseInt(s, 2);
    String tmp = Integer.toBinaryString(i);
    s = tmp.substring(tmp.length()- s.length());

Upvotes: 5

what is sleep
what is sleep

Reputation: 905

maybe this will work:

String result = Integer.toBinaryString(~(Integer.parseInt("0111000000",2)));

converts binary String to int, use bitwise not operator to invert, then convert back to binary string.

Upvotes: 1

Ben Voigt
Ben Voigt

Reputation: 283921

You should use string builder so you are able to change individual bits without creating many many garbage strings. Also you can flip single bits using XOR:

b ^= 1;

Which works on both binary and ASCII values of digits.

Upvotes: 1

user180100
user180100

Reputation:

StringUtils.replaceChars from common-lang might help here:

StringUtils.replaceChars("0111000000", "01", "10");

Upvotes: 1

Alex D
Alex D

Reputation: 30485

Keep track of how many bits there are in your bit-string. After converting to an integer and using a ~value operation to flip the bits, use a bit-mask to remove the unwanted 1 high-end bits.

Say for example your bit-string has a fixed 10 bits. Then you can mask off the unwanted high-end bits with: value & 0x2ff.

If the number of bits in the bit-string is variable:

value & ((1 << nBits) - 1)

Upvotes: 1

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