CODEWITHSUNDEEP
javastringcharcompareto
mike
mike

Reputation: 147

Comparing two strings in java character by character

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?

Upvotes: 9

Views: 117012

Answers (5)

Baz
Baz

Reputation: 36894

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++;    
        }
}

Upvotes: 12

Edward J Beckett
Edward J Beckett

Reputation: 5140

My notes from a java training tutorial requiring string comparison with charAt() and nested loops ... The method could easily be changed to return the non-matching characters from the source string ... but I'll leave that one up to you ... ;-)

public class SubString {

public static boolean findTarget( String target, String source ) {

    int target_len = target.length();
    int source_len = source.length();

    boolean found = false;

    for(int i = 0; ( i < source_len && !found ); ++i) {

    int j = 0;

        while( !found ) {

            if( j >= target_len ) {
                break;
            }

            /**
             * Learning Concept:
             *
             *  String target = "for";
             *  String source = "Searching for a string within a string the hard way.";
             *
             *  1 - target.charAt( j ) :
             *    The character at position 0 > The first character in 'Target' > character 'f', index 0.
             *
             *  2 - source.charAt( i + j) :
             *
             *    The source strings' array index is searched to determine if a match is found for the
             *    target strings' character index position. The position for each character in the target string
             *    is then compared to the position of the character in the source string.
             *
             *    If the condition is true, the target loop continues for the length of the target string.
             *
             *    If all of the source strings' character array element position matches the target strings' character array element position
             *    Then the condition succeeds ..
             */

            else if( target.charAt( j ) != source.charAt( i + j ) ) {
                break;
            } else {
                ++j;
                if( j == target_len ) {
                    found = true;
                }
            }
        }

    }

    return found;

}

public static void main ( String ... args ) {

String target = "for";
String source = "Searching for a string within a string the hard way.";

System.out.println( findTarget(target, source) );

}

}

Upvotes: 0

Andreas Dolk
Andreas Dolk

Reputation: 114817

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++;    
  }
}

Upvotes: 1

kgautron
kgautron

Reputation: 8283

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

Upvotes: 2

Razvan
Razvan

Reputation: 10103

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++;    
}

Upvotes: 8

Related Questions