Search strings in a multi-line string with regex and Java

Question

I am quite disturbed by Java syntax for regex... Here is my (multi-line) string:

2054:(0020,0032) DS #36 [-249.28170196281\-249.28170196281\0] Image Position (
2098:(0020,0037) DS #12 [1\0\0\0\1\0] Image Orientation (Patient)
2118:(0020,0052) UI #52 [1.3.12.2.11...5.2.30.25....2.20....0.0.0]
2178:(0020,1040) LO #0 [] Position Reference Indicator
2222:(0028,0004) CS #12 [MONOCHROME2] Photometric Interpretation
2242:(0028,0010) US #2 [256] Rows
2252:(0028,0011) US #2 [256] Columns
2262:(0028,0030) DS #18 [1.953125\1.953125] Pixel Spacing
2288:(0028,0100) US #2 [16] Bits Allocated
2298:(0028,0101) US #2 [12] Bits Stored
2352:(0028,1055) LO #6 [Algo1] Window Center & Width Explanation

I need 1.953125 and 1.953125 from DS #18 [1.953125\1.953125] Pixel Spacing

I tried this:

Pattern p = Pattern.compile("DS #18 \\[([0-9\\.]*)\\\\([0-9\\.]*)\\] Pixel Spacing"); // os is my string above
System.out.println(m.matches()); // false =(

but without success. Any idea? "Pattern.MULTILINE" do not change anything.

Thanks!

Edson Tirelli · Accepted Answer · 2011-01-28 15:14:23Z

4

If you are trying to extract multiple occurrences from your input string, you can't use the matches() method, as it will try to match the whole input. So for multiple occurrences:

Pattern p = Pattern.compile("DS \\#18 \\[([0-9\\.]*)\\\\([0-9\\.]*)\\] Pixel Spacing",
                            Pattern.MULTILINE|Pattern.DOTALL); 
Matcher m = p.matcher( input );
while( m.find() ) {
    System.out.println("[ "+m.group( 1 )+", "+m.group( 2 )+" ]");
}

If you want a single occurrence, then you need to add .* at the beginning and end of your pattern instead:

Pattern p = Pattern.compile(".*DS \\#18 \\[([0-9\\.]*)\\\\([0-9\\.]*)\\] Pixel Spacing.*",
                            Pattern.MULTILINE|Pattern.DOTALL); 
System.out.println(m.matches());

Edson

answered Jan 28, 2011 at 15:14

Edson Tirelli

3,90122 silver badges23 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

Alan Moore Over a year ago

FYI, the MULTILINE and DOTALL modifiers are unnecessary. MULTILINE alters the meaning of the anchors (^ and $), and DOTALL alters the meaning of the dot (.). Since you aren't using the dot as a metacharacter, and you're not using the anchors at all, neither of those modifiers is relevant.

Edson Tirelli Over a year ago

Yes, only the second example requires the DOTALL. I just usually use both by default when doing multiline matches so that I don't need to worry about adding/removing the options when I change my pattern, but you are right.

Collectives™ on Stack Overflow

Search strings in a multi-line string with regex and Java

1 Answer 1

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related