How to replace a single char at an index by a string?

Question

I have a String "speed,7,red,fast". I want to replace the 7 by a String "Seven". How do I do that ?

More details -

7 can be replaced by ANY string and not just "Seven". It could also be "SevenIsHeaven". I don't want to replace all occurrences of 7. Only 7 at the specified index, ie use the index of 7 to replace 7 by some string.

I feel like you have two questions here. a) What's the best way to convert a `numeric` value to its `alpha` equal? b) How to replace these values? — Menno, Apr 29 '13 at 08:57
http://docs.oracle.com/javase/tutorial/java/data/manipstrings.html — TheDarkKnight, Apr 29 '13 at 08:58
Did you look for "replace string Java" in google? You'll be amazed from the results.. — Maroun, Apr 29 '13 at 08:59
When you say, specified index, do you mean the character index or the index of the string in what looks to be a comma-separated list of strings? — vikingsteve, Apr 29 '13 at 09:02
@vikingsteve - use the index of 7 to replace 7 by some string. The index must be involved in your code. — david blaine, Apr 29 '13 at 09:04

Eugene · Accepted Answer · 2013-04-29T09:08:45.473

7

 replaceAll("7", "Seven") //simple as that

EDIT

Then you should look for the specified index.

 String input = "test 7 speed,7,red,fast yup 7 tr";
    int indexInteresdIn = 13;
    if(input.charAt(indexInteresdIn) == '7'){
        StringBuilder builder = new StringBuilder(input);
        builder.replace(indexInteresdIn, indexInteresdIn+1, "Seven");
        System.out.println(builder.toString());
    }

edited Apr 29 '13 at 09:08

answered Apr 29 '13 at 08:56

Eugene

117,005
15
201
306

My first guess too, though I think OP wants to able to replace all `numeric`s? – Menno Apr 29 '13 at 08:59
2

OP says he only wants to replace the specified occurence of 7, not all. – vikingsteve Apr 29 '13 at 09:00
Ok, so we're just talking about a simple replace of a specified value to another specified value? In that case +1 for this answer. – Menno Apr 29 '13 at 09:01
2

@vikingsteve this is part of the update, it was not originally in the question ;) – Eugene Apr 29 '13 at 09:02

score 4 · Answer 2 · edited May 23 '17 at 10:25

Because String is immutable you should use StringBuilder for better performance.

http://docs.oracle.com/javase/7/docs/api/java/lang/StringBuilder.html

yourStringBuiler.replace(
                   yourStringBuiler.indexOf(oldString),
                   yourStringBuiler.indexOf(oldString) + oldString.length(),
                   newString);`

If you want to replace a whole String like the String.replaceAll() does you could create an own function like this:

public static void replaceAll(StringBuilder builder, String from, String to)
{
    int index = builder.indexOf(from);
    while (index != -1)
    {
        builder.replace(index, index + from.length(), to);
        index += to.length(); // Move to the end of the replacement
        index = builder.indexOf(from, index);
    }
}

Source: Replace all occurrences of a String using StringBuilder?

However if you doesn't need it frequently and performance is not that important a simple String.replaceAll() will do the trick, too.

That only replaces a character for a character. What if he wants to replace a character with a longer string? — vikingsteve, Apr 29 '13 at 09:04

PermGenError · Answer 3 · 2013-04-29T09:02:50.543

2

How about simply like below ?

 String str =  "speed,7,red,fast";
str = str.replace("7", "Seven");

7 can be replaced by ANY string and not just "Seven". It could also be "SevenIsHeaven". I don't want to replace all occurrences of 7. Only 7 at the specified index.

Or if you wanna use regex to replace the first numeric to a meaningful String.

 String str =  "speed,7,red,fast";
str = str.replaceFirst("\\d", "Seven");

edited Apr 29 '13 at 09:02

answered Apr 29 '13 at 08:56

PermGenError

45,977
8
87
106

that replaces all occurences. maybe replaceFirst() instead of replace() ? – vikingsteve Apr 29 '13 at 09:03

score 0 · Answer 4 · answered Apr 29 '13 at 09:52

better way is to store the string itself in an array, spiting it at a space.

String s[];
static int index; 
s = in.readLine().spilt(" ");

Now scan the array for the specified word, at the specified index and replace that with the String you desire.

for(int i =0;i<s.length; i++)
{
 if((s[i] == "7")&&(i==index))
{
  s[i]= "Seven";
}
}

How to replace a single char at an index by a string?

4 Answers4