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
– Thorbjørn Ravn Andersen, Commented Oct 15, 2012 at 22:02
This sounds like exactly what you should expect: it replaces all 'e's with '*'s. — Louis Wasserman
– Louis Wasserman, Commented Oct 15, 2012 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
– JustinKSU, Commented Oct 15, 2012 at 22:03
Do you want your program fixed, or is it OK to show a simpler solution? — Sergey Kalinichenko
– Sergey Kalinichenko, Commented Oct 15, 2012 at 22:04
Logical ANDs must both be true for the answer to be true though. — Matthew Brzezinski
– Matthew Brzezinski, Commented Oct 15, 2012 at 22:05

Jon Skeet · Accepted Answer · 2012-10-15 22:05:18Z

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] = '*';
    }
}

Community · Accepted Answer · 2017-05-23 11:43:14Z

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, 2017 at 11:43

CommunityBot

11 silver badge

answered Oct 15, 2012 at 22:07

JustinKSU

5,0192 gold badges32 silver badges53 bronze badges

Collectives™ on Stack Overflow

Java - Character replacement in a string

2 Answers 2

Comments

Comments

Linked

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

Comments

Linked

Related