Comparing two strings in java character by character

Question

I am beginner in java, I am trying to compare two strings in java char by char and find how many different chars they have by the following code but it doesn't work,

     min is the min between the 2 strings

     for(int i=0; i<min-1; i++){
            s1 = w1.substring(j,j++);
            s2 = w2.substring(j,j++);

            if (! s1.equalsIgnoreCase(s2) ){
                counter++;    
            }
      }`

Any tips?

Answer 1

Use this:

char[] first  = w1.toLowerCase().toCharArray();
char[] second = w2.toLowerCase().toCharArray();

int minLength = Math.min(first.length, second.length);

for(int i = 0; i < minLength; i++)
{
        if (first[i] != second[i])
        {
            counter++;    
        }
}

Answer 2

Use the charAt(index) method and use the '==' operator for the two chars:

c1 = w1.charAt(j);
c2 = w2.charAt(j);

if (c1 == c2) ){
   counter++;    
}

Answer 3

int i =0;
for(char c : w1.toCharArray())){
   if(i < w2.length() && w2.charAt(i++) != c)
     counter++;
}

Answer 4

We can solve the problem with substring. But let's look at your code first:

// assuming, min is the minimum length of both strings,
// then you don't check the char at the last position
for(int j=0; j < min-1; j++) {

  // s1, s2 will always be empty strings, because j++ is post-increment:
  // it will be incremented *after* it has been evaluated
  s1 = w1.substring(j,j++);
  s2 = w2.substring(j,j++);

  if (!s1.equalsIgnoreCase(s2) ){
    counter++;    
  }
}

A solution based on substring could be like that:

for(int j=0; j < min; j++) {
  s1 = w1.substring(j,j+1);
  s2 = w2.substring(j,j+1);

  if (!s1.equalsIgnoreCase(s2) ){
    counter++;    
  }
}