Java - Character replacement in a string

Question

I'm having some troubles the replacement of a character in a string. The code works perfectly fine for the removal of hyphens an periods, however for the letter 'e' it removes the 'e' in "test", and it also converts the three 'e's at the end of the string. Does anyone know why this is happening?

        String str = "This is a test string, 12345! -12e3.0 eee";
    for(int i = 0; i < str.length(); i++) {
        if((str.charAt(i) == '-') && (Character.isDigit(str.charAt(i+1)))) {
            str = str.replace(str.charAt(i), '*');
        }

        if((str.charAt(i) == 'e') && (Character.isDigit(str.charAt(i+1)))) {
            str = str.replace(str.charAt(i), '*');
        }

        if((str.charAt(i) == '.') && (Character.isDigit(str.charAt(i+1)))) {
            str = str.replace(str.charAt(i), '*');
        }
    }
    str = str.replaceAll("[1234567890]", "*");
    System.out.println(str);

Perhaps you should write out the contents of `str` at the end of the for-loop. Then you can see what happens when. — Thorbjørn Ravn Andersen, Oct 15 '12 at 22:02
This sounds like exactly what you should expect: it replaces all 'e's with '*'s. — Louis Wasserman, Oct 15 '12 at 22:02
Unrelated you may have an issue if i is the last character and you try to evaluate str.charAt(i+1) — JustinKSU, Oct 15 '12 at 22:03
Do you want your program fixed, or is it OK to show a simpler solution? — Sergey Kalinichenko, Oct 15 '12 at 22:04
Logical ANDs must both be true for the answer to be true though. — Matthew Brzezinski, Oct 15 '12 at 22:05
Might be a duplicate of http://stackoverflow.com/questions/6952363/java-replace-a-character-at-a-specific-index-in-a-string — scrappedcola, Oct 15 '12 at 22:11

score 3 · Accepted Answer · answered Oct 15 '12 at 22:05

In each case, the if part just finds whether the character should be replaced... but then the replacement itself:

str = str.replace(str.charAt(i), '*')

... performs that replacement for the whole of the string.

The simplest fix to this is probably to convert it to an array of characters to start with, replace one character at a time, and then create a string for the rest:

char[] chars = str.toCharArray();
for (int i = 0; i < chars.length - 1; i++) {
    if (chars[i] == '-' && Character.isDigit(chars[i + 1])) {
        chars[i] = '*';
    }
    // Similarly for the other two
}
String newString = new String(chars);

Or to avoid the duplication, replace the middle section with:

for (int i = 0; i < chars.length - 1; i++) {
    if (Character.isDigit(chars[i + 1]) &&
        (chars[i] == '-' || chars[i] == 'e' || chars[i] == '.')) {
        chars[i] = '*';
    }
}

score 0 · Answer 2 · edited May 23 '17 at 11:43

0

str.replace(str.charAt(i), '*'); will replace all characters. Javadoc

You can use a StringBuilder to replace a specific character in a String. Please review this question and answer.

Replace a character at a specific index in a string?

edited May 23 '17 at 11:43

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answered Oct 15 '12 at 22:07

JustinKSU

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Java - Character replacement in a string

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