Wrong output using replaceall

Question

Why do i get \"AAAAAAAAA\" instead of \"1A234A567\" from following Code:

String myst = \"1.234.567\";

String test = myst.replaceAll(\".\", \"A\");

System.o         


        

Answer 1

Try this:

String test = myst.replace(".", "A");

The difference: replaceAll() interprets the pattern as a regular expression, replace() interprets it as a string literal.

Here's the relevant source code from java.lang.String (indented and commented by me):

public String replaceAll(String regex, String replacement) {
    return Pattern.compile(regex)
                  .matcher(this)
                  .replaceAll(replacement);
}


public String replace(CharSequence target, CharSequence replacement) {
    return Pattern.compile(
              target.toString(),
              Pattern.LITERAL /* this is the difference */
           ).matcher(this)
            .replaceAll(
                Matcher.quoteReplacement(
                    /* replacement is also a literal,
                       not a pattern substitution */
                    replacement.toString()
            ));
}

Reference:

• String.replaceAll(String, String)
• String.replace(CharSequence, CharSequence)
• Pattern.LITERAL

Answer 2

replaceAll function take a regular expression as parameter. And the regular expression "." means "any character". You have to escape it to specify that it is the character you want : replaceAll("\\.", "A")

Answer 3

Because every single char of the input matches the regexp pattern (.). To replace dots, use this pattern: \. (or as a Java String: "\\.").

Answer 4

You need to escape .

make it

String myst = "1.234.567";

String test = myst.replaceAll("\\.", "A");

System.out.println(test);