Java pattern Match for a specific pattern to match

Question

i try to match a pattern in a given string which will be static, following is my program:

package com.test.poc;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class RegexTestPatternMatcher {
  public static final String EXAMPLE_TEST = "http://localhost:8080/api/upload/form/{uploadType}/{uploadName}";

  public static void main(String[] args) {
    Pattern pattern = Pattern.compile("{\\w+}");
    // In case you would like to ignore case sensitivity you could use this
    // statement
    // Pattern pattern = Pattern.compile("\\s+", Pattern.CASE_INSENSITIVE);
    Matcher matcher = pattern.matcher(EXAMPLE_TEST);
    // Check all occurance
    while (matcher.find()) {
      System.out.print("Start index: " + matcher.start());
      System.out.print(" End index: " + matcher.end() + " ");
      System.out.println(matcher.group());
    }
    // Now create a new pattern and matcher to replace whitespace with tabs
    Pattern replace = Pattern.compile("\\s+");
    Matcher matcher2 = replace.matcher(EXAMPLE_TEST);
    System.out.println(matcher2.replaceAll("\t"));
  }
} 

i try to match strings available in {} and replace them with some value.

but it gives me this exception :

Exception in thread "main" java.util.regex.PatternSyntaxException: Illegal repetition
{\w+}
    at java.util.regex.Pattern.error(Pattern.java:1713)
    at java.util.regex.Pattern.closure(Pattern.java:2775)
    at java.util.regex.Pattern.sequence(Pattern.java:1889)
    at java.util.regex.Pattern.expr(Pattern.java:1752)
    at java.util.regex.Pattern.compile(Pattern.java:1460)
    at java.util.regex.Pattern.<init>(Pattern.java:1133)
    at java.util.regex.Pattern.compile(Pattern.java:823)
    at com.test.poc.RegexTestPatternMatcher.main(RegexTestPatternMatcher.java:9)

what could be problem i make here. i am sorry to ask this here

Answer 1

{ and } are reserved characters. You will need to escape those: \\{ and \\}

For reference, these characters are used for repetition.

http://www.regular-expressions.info/repeat.html

Edit

I don't believe you can do a simple replacement using this style of matching. What you can do is to build a new string, successively looking up each match:

public static void main( String[] args ) {
    String toConvert = EXAMPLE_TEST;

    Pattern pattern = Pattern.compile("\\{\\w+\\}");
    // In case you would like to ignore case sensitivity you could use this
    // statement
    // Pattern pattern = Pattern.compile("\\s+", Pattern.CASE_INSENSITIVE);
    Matcher matcher = pattern.matcher(toConvert);
    StringBuilder resultStringBuilder = new StringBuilder();
    int startPos = 0;
    while (matcher.find()) {

        // append everything up to this match.
        resultStringBuilder.append(toConvert.substring(startPos, matcher.start()));

        // append the replacement
        resultStringBuilder.append(lookup(matcher.group()));

        // set the start pos for the next match
        startPos = matcher.end();
    }
    // append everything that's left.
    resultStringBuilder.append(toConvert.substring(startPos, toConvert.length()));        


    String resultStrig = resultStringBuilder.toString();
    System.out.println(resultStrig);
}


private static String lookup( String s ) {
    // decide what you want to replace this string with
    // You might want to make use of a TreeMap<String,String> here.
    return "";
}

Answer 2

Try this :

Pattern pattern = Pattern.compile("\\{\\w+\\}");