JavaScript or Java String Subtraction

Question

If you are using Java or JavaScript, is there a good way to do something like a String subtraction so that given two strings:

org.company.project.component
org.company.project.component.sub_component

you just get

sub_component

I know that I could just write code to walk the string comparing characters, but I was hoping there was a way to do it in really compact way.

EDIT TO ADD: As I was analyzing the data I get when I use this I realized that I missed the statement of the case a bit. It should be:

org.company.project.component.diff
org.company.project.component.sub_component

So, I actually only want to remove the sections that are identical. That said, the answer that I accepted is closest to my goal.

Answer 1

String result = "org.company.project.component.sub_component".replace("org.company.project.component","")

Should work...

EDIT: Apache commons libraries are also great to use

As noted below, the StringUtils class does in fact have a method for this: StringUtils.remove()

Answer 2

Can't you just replace the occurrences of the first string in the second with an empty string ?

Answer 3

Depends on precisely what you want. If you're looking for a way to compare strings in the general case -- meaning finding common sub-strings between arbitrary inputs -- then you're looking at something closer to the Levenshtein distance and similar algorithms. However, if all you need is prefix/suffix comparison, this should work:

public static String sub(String a, String b) {
    if (b.startsWith(a)) {
        return b.subString(a.length());
    }

    if (b.endsWith(a)) {
        return b.subString(0, b.length() - a.length());
    }

    return "";
}

...or something roughly to that effect.

Answer 4

If you're just trying to get whatever's after the last dot, I find this method easy in Javascript:

var baseString = "org.company.project.component.sub_component";
var splitString = baseString.split(".");
var subString = splitString[splitString.length - 1];

subString will contain the value you're looking for.

Answer 5

At first glance, I thought of RegExp, but adding to the question, you removed that possibility by adding to the start-string ...

So you'll have to make a procedure, that takes every character that are equal out of the resulting string, something like this:

<script type="text/javascript">
var a = "org.company.project.component.diff";
var b = "org.company.project.component.sub_component";
var i = 0;
while(a.charAt(i) == b.charAt(i)){
  i++;
}
alert(b.substring(i));
</script>

By the way it doesn't have a meaning to set Java and javascript as equals in any context, a popular way of putting it could be:

Java and javascript has four things in common: j - a - v - a !-)

Answer 6

function sub(a, b) {
  return [a, b].join('\x01').match(/^([^\x01]*)[^\x01]*\x01\1(.*)/)[2];
}

Though this relies on that the character with code 1 does not appear in any of those strings.