Issue with string.replaceAll

Question

I'm just trying to replace a string \\ with \\\\

Below is the program but it is terminating

String path="\\dctmadmin\\Human Resource\\Training\\Procedures\\Formalities\\Legalities\\Material";         

long start = System.currentTimeMillis();
// replace this string \\ with \\\\
String formatedPath = path.replaceAll("\\\\", "\\\\\\\\");
System.out.println(" string after formatting using replaceAll = "+formatedPath);
long end = System.currentTimeMillis();
System.out.println(" time take in milli seconds for String.replaceAll = "+Long.toString(end-start) );

Please let me know the mistake i was doing.

Long.toString(end-start) is not neccessary. (end-start) will suffice. — John Dvorak
– John Dvorak, Commented Nov 2, 2012 at 8:48
Its giving Thread[main] (suspended Exception PatternSyntaxException) — JavaGeek
– JavaGeek, Commented Nov 2, 2012 at 8:50
Since you don't require any regex functionality, think about using String.replace(String, String) instead of String.replaceAll(String, String) — Sean Patrick Floyd
– Sean Patrick Floyd, Commented Nov 2, 2012 at 8:50
In your String, all \\ are really one \ inside the String. Your replaceAll gives a String with two real \\, so it´s OK. Test doing System.out.println("\\dctmadmin\\Human Resource\\Training\\Procedures\\Formalities\\Legalities\\Material") and System.out.println("\\drt...\\Material".replaceAll(...)) — Chuidiang
– Chuidiang, Commented Nov 2, 2012 at 8:53

Ian Roberts · Accepted Answer · 2012-11-02 08:57:40Z

3

For a literal string replacement where you don't need the power of regular expressions you should use replace rather than replaceAll as it's simpler and more efficient.

// replace single backslash with double
String formatedPath = path.replace("\\", "\\\\");

answered Nov 2, 2012 at 8:57

Ian Roberts

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2 Comments

JavaGeek Over a year ago

Yes. It works but is it possible to display output as \\\\dctmadmin\\\\Human Resource\\\\Training\\\\Procedures\\\\Formalities\\\\Legalities\\\\Material

JavaGeek Over a year ago

as per Polppan suggestion i changed it to String formatedPath = path.replaceAll("\\\\", "\\\\\\\\\\\\\\\\"); and then its displaying \\\\dctmadmin\\\\Human Resource\\\\Training\\\\Procedures\\\\Formalities\\\\Legalities\\\\Material

Chuidiang · Accepted Answer · 2012-11-02 08:57:24Z

1

Your real String contains only one \. Test

System.out.println("\\dctmadmin\\Human Resource\\Training\\Procedures\\Formalities\\Legalities\\Material");

So your replaceAll is running OK if it returns double \\ when System.out.println("your string".replaceAll(...));

answered Nov 2, 2012 at 8:57

Chuidiang

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Comments

Jacob · Accepted Answer · 2012-11-02 08:58:07Z

1

Try as

String path = 
    "\\dctmadmin\\Human Resource\\Training\\Procedures\\Formalities\\Legalities\\Material";


long start = System.currentTimeMillis();
// replace this string \\ with \\\\

String formatedPath = path.replaceAll("\\\\", "\\\\\\\\\\\\\\\\");

System.out.println(" string after formatting using replaceAll = " + 
                   formatedPath);


long end = System.currentTimeMillis();

System.out.println(" time take in milli seconds for String.replaceAll = " + Long.toString(end - start));

System.out.println(" path  "+formatedPath);

answered Nov 2, 2012 at 8:58

Jacob

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1 Comment

JavaGeek Over a year ago

Your cde works and displays output as \\\\dctmadmin\\\\Human Resource\\\\Training\\\\Procedures\\\\Formalities\\\\Legalities\\\\Material

PermGenError · Accepted Answer · 2012-11-02 08:54:46Z

in your string when you say \ it actually means \ escaped by another \, thus it is replacing it correctly.

String path="\\dctmadmin\\Human Resource\\Training\\Procedures\\Formalities\\Legalities\\Material";

         System.out.println("String before: "+ path);
        long start = System.currentTimeMillis();
        // replace this string \\ with \\\\

          String formatedPath = path.replaceAll("\\\\", "\\\\\\\\");

          System.out.println(" string after formatting using replaceAll = "+formatedPath);

output i got

   String before:  \dctmadmin\Human Resource\Training\Procedures\Formalities\Legalities\Material

     string after formatting using replaceAll = \\dctmadmin\\Human Resource\\Training\\Procedures\\Formalities\\Legalities\\Material
     time take in milli seconds for String.replaceAll = 2

Joop Eggen · Accepted Answer · 2012-11-02 09:08:37Z

0

You did right. In Java string \\ represents one backslash, in regex it is the non-String escape.

    String formatedPath = path.replaceAll("\\\\", "\\\\\\\\");
    System.out.println("path         = " + path);
    System.out.println("formatedPath = " + formatedPath);

gives

path         = \dctmadmin\Human Resource\Training\Pr...s\Form...s\L...s\Material
formatedPath = \\dctmadmin\\Human Resource\\Training\\Pr..s\\Form...s\\Material

answered Nov 2, 2012 at 9:08

Joop Eggen

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Comments

robert · Accepted Answer · 2012-11-02 09:09:20Z

0

Output of

string after formatting using replaceAll = \\dctmadmin\\Human Resource\\Training\\Procedures\\Formalities\\Legalities\\Material

is correct. It looks like it hasn't changed because you're discounting the fact that the '\' in your original are escaped :)

answered Nov 2, 2012 at 9:09

robert

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