CODEWITHSUNDEEP
javaregexstringreplaceall
Ronaldinho Learn Coding
Ronaldinho Learn Coding

Reputation: 13824

Java replaceAll() method

I am trying to understand this piece of codes:

for (File f : files) {
     fileName = f.getName().toUpperCase().replaceAll("_\\d\\d\\d\\d_\\d\\d_\\d\\d_\\d\\d_\\d\\d", "");

     if (fileName.equals(tableName + ".XML")) {
         returnFile = f;
         break;
     }
}

and I am stuck at this part: replaceAll("_\\d\\d\\d\\d_\\d\\d_\\d\\d_\\d\\d_\\d\\d", "")

as far as I know it is trying to remove something from the name (maybe the underscore "_" ) but what exactly is _\\d\\d\\d\\d_\\d\\d_\\d\\d_\\d\\d_\\d\\d

Can somebody please explain?

Upvotes: 1

Views: 332

Answers (3)

Sebastian Paaske Tørholm
Sebastian Paaske Tørholm

Reputation: 50968

str.replaceAll("_\\d\\d\\d\\d_\\d\\d_\\d\\d_\\d\\d_\\d\\d", "") takes the string str and replaces all matches of the regular expression _\d\d\d\d_\d\d_\d\d_\d\d_\d\d with nothing (i.e. ""). (The reason it is written \\d and not \d is that the \ is escaped.)

In this case, \d means "a digit". So, more than likely, it removes a date/time from the string. For an example, if str is "screenshot_from_stackoverflow_2016_03_30_23_47.jpg", it becomes screenshot_from_stackoverflow.jpg after the replaceAll.

To get a feel for regular expressions, how they work and what they can do, I would recommend reading up on them, for instance on regular-expressions.info. It has a pretty comprehensive tutorial available.

Upvotes: 2

K139
K139

Reputation: 3679

\d - matches a digit [0-9]

Java RegEx

Upvotes: 1

ninja.coder
ninja.coder

Reputation: 9658

as far as I know it is trying to remove something from the name (maybe the underscore "_" ) but what exactly is \d\d\d\d\d\d_\d\d_\d\d_\d\d

It is the pattern which will match the digits [0-9] in this format _XXXX_XX_XX_XX_ and replace it with "" i.e. nothing.

For Example,

_7686_77_78_77_77
_0123_65_58_56_12

Will be replaced in your string with "".

Upvotes: 1

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