Adding binary numbers

Question

Does anyone know how to add 2 binary numbers, entered as binary, in Java?

For example, 1010 + 10 = 1100.

Answer 1

You can just put 0b in front of the binary number to specify that it is binary.

For this example, you can simply do:

Integer.toString(0b1010 + 0b10, 2);

This will add the two in binary, and Integer.toString() with 2 as the second parameter converts it back to binary.

Answer 2

Another interesting but long approach is to convert each of the two numbers to decimal, adding the decimal numbers and converting the answer obtained back to binary!

Answer 3

i tried to make it simple this was sth i had to deal with with my cryptography prj its not efficient but i hope it

    public String binarysum(String a, String b){
    int carry=0;
    int maxim;
    int minim;
    maxim=Math.max(a.length(),b.length());
    minim=Math.min(a.length(),b.length());         
    char smin[]=new char[minim];
    char smax[]=new char[maxim];
    if(a.length()==minim){
     for(int i=0;i<smin.length;i++){
     smin[i]=a.charAt(i);
      }
      for(int i=0;i<smax.length;i++){
       smax[i]=b.charAt(i);
      }
      }
      else{
          for(int i=0;i<smin.length;i++){
          smin[i]=b.charAt(i);
             }
       for(int i=0;i<smax.length;i++){
       smax[i]=a.charAt(i);
      } 
      }
    char[]sum=new char[maxim];
    char[] st=new char[maxim];
    for(int i=0;i<st.length;i++){
    st[i]='0';
    }
    int k=st.length-1;
   for(int i=smin.length-1;i>-1;i--){
    st[k]=smin[i];
    k--;
    } 

     //   *************************** sum begins here
   for(int i=maxim-1;i>-1;i--){
   char x= smax[i];
   char y= st[i];
    if(x==y && x=='0'){
         if(carry==0)
             sum[i]='0';
         else if(carry==1){
             sum[i]='1';
             carry=0;
    }
   }
    else if(x==y && x=='1'){
        if(carry==0){
            sum[i]='0';
            carry=1;
        }
        else if(carry==1){
          sum[i]='1';
          carry=1;
        }
     }
     else if(x!=y){
        if(carry==0){
            sum[i]='1';
            }
        else if(carry==1){
          sum[i]='0';
          carry=1;
        }
       }        }
      String s=new String(sum);
     return s;
      }

Answer 4

I've actually managed to find a solution to this question without using the stringbuilder() function. Check this out:

public void BinaryAddition(String s1,String s2)
{
    int l1=s1.length();int c1=l1;
    int l2=s2.length();int c2=l2;
    int max=(int)Math.max(l1,l2);
    int arr1[]=new int[max];
    int arr2[]=new int[max];
    int sum[]=new int[max+1];
    for(int i=(arr1.length-1);i>=(max-l1);i--)
    {
        arr1[i]=(int)(s1.charAt(c1-1)-48);
        c1--;
    }
    for(int i=(arr2.length-1);i>=(max-l2);i--)
    {
        arr2[i]=(int)(s2.charAt(c2-1)-48);
        c2--;
    }
    for(int i=(sum.length-1);i>=1;i--)
    {
        sum[i]+=arr1[i-1]+arr2[i-1];
        if(sum[i]==2)
        {
            sum[i]=0;
            sum[i-1]=1;
        }
        else if(sum[i]==3)
        {
            sum[i]=1;
            sum[i-1]=1;
        }
    }
    int c=0;
    for(int i=0;i<sum.length;i++)
    {
        System.out.print(sum[i]);
    }
}

Answer 5

you can write your own One.

long a =100011111111L;
long b =1000001111L;

int carry = 0 ;
long result = 0;

long multiplicity = 1;

while(a!=0 || b!=0 || carry ==1){
    if(a%10==1){
        if(b%10==1){
            result+= (carry*multiplicity);
            carry = 1;
        }else if(carry == 1){
            carry = 1;  
        }else{
            result += multiplicity;
        }
    }else if (b%10 == 1){
        if(carry == 1){
            carry = 1;
        }else {
            result += multiplicity; 
        }
    }else {
        result += (carry*multiplicity);
        carry = 0;
    }

    a/=10;
    b/=10;
    multiplicity *= 10;

}


System.out.print(result);

it works just by numbers , no need string , no need SubString and ...

Answer 6

The original solution by Martijn will not work for large binary numbers. The below code can be used to overcome that.

public String addBinary(String s1, String s2) {
    StringBuilder sb = new StringBuilder();
    int i = s1.length() - 1, j = s2.length() -1, carry = 0;
    while (i >= 0 || j >= 0) {
        int sum = carry;
        if (j >= 0) sum += s2.charAt(j--) - '0';
        if (i >= 0) sum += s1.charAt(i--) - '0';
        sb.append(sum % 2);
        carry = sum / 2;
    }
    if (carry != 0) sb.append(carry);
    return sb.reverse().toString();
}