How replaceAll "/" in java String to format URL?

Question

String url = "d://test////hello\\\hello";
String separator = File.separator;
url = url.replaceAll("\\*", separator);
url = url.replaceAll("/+", separator);

I want to format those url, but error occurs when i attempt to use replaceAll("/+", separator). and i attempt to escaped "/" as "\\/", it still doesn't work..

This is the Exception from console:

Exception in thread "main" **java.lang.StringIndexOutOfBoundsException**: String index out of range: 1
    at java.lang.String.charAt(String.java:686)
    at java.util.regex.Matcher.appendReplacement(Matcher.java:703)
    at java.util.regex.Matcher.replaceAll(Matcher.java:813)
    at java.lang.String.replaceAll(String.java:2189)

Now it works

 String separator = null;
 if(File.separator.equals("/")) {
    separator = "/";
    url = url.replaceAll("/+", separator);
    url = url.replaceAll("\\\\+", separator);
 } else {
    separator = Matcher.quoteReplacement(File.separator);
    url = url.replaceAll("/+", separator);
    url = url.replaceAll("\\+", separator);
 }

:) it works in javascript

var i = "d:\\ad////df";
alert(i.replace(/\/+/g, '\\'));

it is out of bound exception, try to check the java.lang.StringIndexOutOfBoundsException: String index out of range: 1 at java.lang.String.charAt(String.java:686) at — goravine
– goravine, Commented Mar 11, 2013 at 3:04

Stephen C · Accepted Answer · 2013-03-11 03:23:38Z

3

Your platform is Windows right? So File.separator will be a backslash right?

The explanation is that the 2nd argument of String.replaceAll is not a simple String. Rather it is a replacement pattern ...

The javadoc says:

"Note that backslashes (\) and dollar signs ($) in the replacement string may cause the results to be different than if it were being treated as a literal replacement string; see Matcher.replaceAll. Use Matcher.quoteReplacement(java.lang.String) to suppress the special meaning of these characters, if desired. "

So your replacement String that consists of a single backslash is an invalid literal replacement string. You need to quote the separator String ... like the javadoc says.

_{(It is a little surprising that you get that particular exception. I can imagine how it could happen, but I'd have thought that they'd deal with bad escapes more elegantly. Mind you, if this was reported as a "bug", Oracle would probably not fix it. A fix would break backwards compatibility.)}

edited Mar 11, 2013 at 3:23

answered Mar 11, 2013 at 3:11

Stephen C

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1 Comment

Walter Lee Over a year ago

Follow your tips, now it works properly, Thank you very much.

Bhesh Gurung · Accepted Answer · 2013-03-11 03:03:32Z

3

Try:

url = url.replaceAll("\\\\+", separator);

You need 4 backward slashes. Escape once for Java string and once for regex meta-character. That is for regex you need two backward slashes \\, and in string you need to escape both of them with another two.

Also, the quantifier * means zero or more, you need to use +.

answered Mar 11, 2013 at 3:03

Bhesh Gurung

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2 Comments

Walter Lee Over a year ago

Thanks you, - - but it throws the same exception.

Bhesh Gurung Over a year ago

It works for me, but I am using Ubuntu. Check out @Stephen's answer also. The end result in my case is d:/test/hello/hello.

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