How to replace a specific string in Java?

Question

I usually don't ask for help but here I really need it.
I have the following code example:

String text = "aa aab aa aab";
text = text.replace("aa", "--");
System.out.println(text);

Console output: -- --b -- --b

I have a question, how do I only replace aa parts of the string not aab included.
So the console output is:

-- aab -- aab

I have another example:

String text = "111111111 1";
text = text.replace("1", "-");
System.out.println(text);

Console output: --------- -

I only want to replace a single character, not all the same ones who are placed together.
So the console output is:

111111111 -

Are there any Java shortcuts for situations like these? I can't figure it out, how to only replace specific part of the string.
Any help would be appreciated :)

Elliott Frisch · Accepted Answer · 2016-07-17 17:25:15Z

1

You could use a regular expression with String.replaceAll(String, String). By using word boundaries (\b), something like

String[] texts = { "aa aab aa aab", "111111111 1" };
String[] toReplace = { "aa", "1" };
String[] toReplaceWith = { "--", "-" };
for (int i = 0; i < texts.length; i++) {
    String text = texts[i];
    text = text.replaceAll("\\b" + toReplace[i] + "\\b", toReplaceWith[i]);
    System.out.println(text);
}

Outputs (as requested)

-- aab -- aab
111111111 -

answered Jul 17, 2016 at 17:25

Elliott Frisch

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Comments

Dici · Accepted Answer · 2016-07-17 17:29:25Z

0

You can use a regex

String text = "111111111 1";
text = text.replaceAll("1(?=[^1]*$)", "");
System.out.println(text);

Explanation:

String.replaceAll takes a regex contrarily to String.replace which takes a litteral to replace
(?=reg) the right part of the regex must be followed by a string matching the regex reg, but only the right part will be captured
[^1]* means a sequence from 0 to any number of characters different from '1'
$ means the end of the string is reached

In plain english, this means: Please replace by an empty string all the occurrences of the '1' character followed by any number of characters different from '1' until the end of the string.

edited Jul 17, 2016 at 17:29

answered Jul 17, 2016 at 17:18

Dici

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1 Comment

Dici Over a year ago

Looking at other answers, I may have misunderstood the question. Keeping for the record

Madan Reddy · Accepted Answer · 2016-07-17 17:37:33Z

We can use the StringTokenizer present in Java to acheive the solution for any kind of input. Below is the sample solution,

public class StringTokenizerExample {

/**
 * @param args
 */
public static void main(String[] args) {
    String input = "aa aab aa aab";
    String output = "";
    String replaceWord = "aa";
    String replaceWith = "--";
    StringTokenizer st = new StringTokenizer(input," ");
    System.out.println("Before Replace: "+input);
    while (st.hasMoreElements()) {
        String word = st.nextElement().toString();
        if(word.equals(replaceWord)){
            word = replaceWith;
            if(st.hasMoreElements()){
                word = " "+word+" ";
            }else{
                word = " "+word;
            }
        }
        output = output+word;
    }
    System.out.println("After Replace: "+output);
}

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