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up vote 10 down vote favorite

I am reading in a string

Is Mississippi a State where there are many systems.

I would like to replace the 1st "s" or "S" in each word with "t" or "T" (i.e keeping the same case)...so that the output is:

It Mitsissippi a Ttate where there are many tystems.

I have tried

s= s.replaceFirst("(?i)S", "t"); [which of course didn't work]

and have experimented trying to split the string using a string [] .split(Pattern.quote("\\s")) then trying to figure out how to replaceFirst() each element of the array and then return the values back to a string [but couldn't figure out the right way of doing it].

I thought \\G might help to restart at the next word but have gotten no where. Any help using these 3 methods is appreciated.

share|improve this question
1  
Why do you replace 'Is' to 'It' if you only need to replace the 1st 's' or 'S' in each work ? Can you correct the layout and give one or more clear example ? – Benoit Vanalderweireldt 4 hours ago
1  
Got it the first occurence of each 's' or 'S' – Benoit Vanalderweireldt 4 hours ago
    
@Hedgebox I hope you have got your answer. But have provided a different approach to solve your problem. See my answer. – mmuzahid 3 hours ago
up vote 7 down vote

One option would be to split the string into words, and then use String.replaceFirst() on each word to replace the first occurrence of s with t (or any other letter you want):

Update:

I refactored my solution to find the first occurrence of any s (upper or lower case), and to apply the appropriate conversion on it.

String input = "Is Mississippi a State where there are many systems.";
String[] parts = input.split(" ");
StringBuilder sb = new StringBuilder("");

for (int i=0; i < parts.length; ++i) {
    if (i > 0) {
        sb.append(" ");
    }
    int index = parts[i].toLowerCase().indexOf('s');
    if (index >= 0 && parts[i].charAt(index) == 's') {
        sb.append(parts[i].replaceFirst("s", "t"));
    }
    else {
        sb.append(parts[i].replaceFirst("S", "T"));
    }
}

System.out.println(sb.toString());

Output:

It Mitsissippi a Ttate where there are many tystems.
share|improve this answer
1  
@im-biegeleisen your solution is perfect with some adjustments. Check my post – Thush-Fdo 3 hours ago
1  
This gets the wrong result for a word like "Systems" with a capital "S" and lower case "s" (at least as I understood the question). – msandiford 3 hours ago
    
Systems -> Tyttems ... what is the problem? – Tim Biegeleisen 3 hours ago
    
@Tim Biegeleisen : msandiford seems to be correct... I just tried it...I would want "Systems" to become "Tystems"... only the 1st occurance of either "S" or "s" to "T" or "t" – Hedgebox 2 hours ago
    
@Hedgebox I updated my answer per your requirements. – Tim Biegeleisen 2 hours ago
up vote 4 down vote

Approach-1: Without using replace and split method for better performance.

String str = "Is Mississippi a State where there are many systems.";
System.out.println(str);

char[] cArray = str.toCharArray();
boolean isFirstS = true;
for (int i = 0; i < cArray.length; i++) {
    if ((cArray[i] == 's' || cArray[i] == 'S') && isFirstS) {
        cArray[i] = (cArray[i] == 's' ? 't' : 'T');
        isFirstS = false;
    } else if (Character.isWhitespace(cArray[i])) {
        isFirstS = true;
    }
}
str = new String(cArray);

System.out.println(str);

EDIT: Approach2 As you need to use replaceFirst method and you dont want to use StringBuilder here is an option for you:

String input = "Is Mississippi a State where there are many Systems.";
String[] parts = input.split(" ");
String output = "";

for (int i = 0; i < parts.length; ++i) {
    int smallS = parts[i].indexOf("s");
    int capS = parts[i].indexOf("S");

    if (smallS != -1 && (capS == -1 || smallS < capS))
        output += parts[i].replaceFirst("s", "t") + " ";
    else
        output += parts[i].replaceFirst("S", "T") + " ";
}

System.out.println(output); //It Mitsissippi a Ttate where there are many Tystems.
share|improve this answer
    
@cricket_007 is it OK now? – mmuzahid 3 hours ago
    
@cricket_007 edited by going to different approach :) – mmuzahid 3 hours ago
    
ASCII shifting... It'll work, but it is very specific to this one problem – cricket_007 3 hours ago
    
@cricket_007 yes.... but I hope this will provide a faster solution than other answer. – mmuzahid 3 hours ago
    
@mmuzahid: tks for your solution but I am trying to get a better understanding of the uses of replaceFirst...without the use of StringBuilder at this point. – Hedgebox 2 hours ago
up vote 3 down vote

Use below amendment to Tim Biegeleisen's answer (before editing his post)

String input = "Is Mississippi a State where there are many systems.";
String[] parts = input.split(" ");
StringBuilder sb = new StringBuilder("");

for (String part : parts) {
    sb.append(part.replaceFirst("s", "t").replaceFirst("S", "T"));
    sb.append(" ");
}

System.out.println(sb.toString());

Edit - You can use concat()

String input = "Is Mississippi a State where there are many systems.";
String[] parts = input.split(" ");

String output = "";

for (String part : parts) {
    output = output.concat(part.replaceFirst("s", "t").replaceFirst("S", "T") + " ");
}

    System.out.println(output);

Update

    String input = "Is Mississippi a State where there are many Systems.";
    String[] parts = input.split(" ");
    //StringBuilder sb = new StringBuilder("");

    String output = "";

    for (String part : parts) {
        output = output.concat(part.replaceFirst("s", "t") + " ");
    }

    String[] parts2 = input.split(" ");

    output = "";

    for (String part : parts2) {
        output = output.concat(part.replaceFirst("S", "T") + " ");
    }
    System.out.println(output);
share|improve this answer
1  
I do want to use String methods...is there a way to do it without using StringBuilder? – Hedgebox 3 hours ago
1  
@hedgebox : check edit part – Thush-Fdo 3 hours ago
1  
Perfect many tks. – Hedgebox 3 hours ago
2  
@Hedgebox FYI StringBuilder provides better performance than + – mmuzahid 3 hours ago
    
@Thush-Fdo: msandiford in his comment below...seems to be correct... I just tried it...I would want "Systems" to become "Tystems"... only the 1st occurance of either "S" or "s" to "T" or "t". When I changes "systems" to "Systems" the code produced "Tyttems" not "Tystems". – Hedgebox 2 hours ago
up vote 1 down vote

My method would be less dependent on those string methods you've mentioned.

String phrase;
String [] parts = phrase.split(" ");

for (int i = 0; i < parts.length; i++ ) {
    for (int j = 0; j < parts[i].length(); j++) {
        if (parts[i].charAt(j) == 's') {
            parts[i] = "t" + parts[i].substring(1);
            break;
        } else if (parts[i].charAt(0) == 'S') {
            parts[i] = "T" + parts[i].substring(1);
            break;
        }
    }
}

String modifiedPhrase = "";

for (int i = 0; i < parts.length; i++ ) {
    modifiedPhrase += parts[i] + " ";
}
share|improve this answer

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