With this example we are going to demonstrate how to find duplication in Strings. In order to check if there are duplications in a String we have created a Matcher against a specified Pattern and used the Matcher API in boolean hasDuplicateWord(String phrase) method. In short the steps of the method are:
- Compile a String regular expression to a Pattern, using
compile(String regex)API method of Pattern. The regular expression used is a word boundary followed by a word character one or more times, followed by the digit 1 and then again a word boundary. - Use
matcher(CharSequence input)API method of Pattern to create a Matcher that will match the given String input against this pattern. - While the matcher finds the next subsequence of the input sequence that matches the pattern, with
find()API method of Matcher get the input subsequence matched, withgroup()API method of Matcher and print it.
Let’s take a look at the code snippet that follows:
package com.javacodegeeks.snippets.core;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
import java.util.regex.PatternSyntaxException;
public class FindDup {
public static void main(String args[]) {
hasDuplicateWord("pizza pizza");
hasDuplicateWord("Faster pussycat kill kill");
hasDuplicateWord("The mayor of of simpleton");
hasDuplicateWord("Never Never Never Never Never");
hasDuplicateWord("222 2222");
hasDuplicateWord("sara sarah");
hasDuplicateWord("Faster pussycat kill, kill");
hasDuplicateWord(". .");
}
public static boolean hasDuplicateWord(String phrase) {
boolean retval = false;
String duplicatePattern = "\b(\\w+))\1\b";
Pattern p = null;
try {
p = Pattern.compile(duplicatePattern);
} catch (PatternSyntaxException pex) {
pex.printStackTrace();
System.exit(0);
}
int matches = 0;
Matcher m = p.matcher(phrase);
String val = null;
while (m.find()) {
retval = true;
val = ":" + m.group() + ":";
System.out.println(val);
matches++;
}
String msg = " NO MATCH: pattern:" + phrase
+ "rn
regex: " + duplicatePattern;
if (retval) {
msg = " MATCH : pattern:" + phrase + "rn
regex: "
+ duplicatePattern;
}
System.out.println(msg + "rn");
return retval;
}
}
Output:
:pizza pizza:
MATCH : pattern:pizza pizza
regex: b(w+) 1b
:kill kill:
MATCH : pattern:Faster pussycat kill kill
regex: b(w+) 1b
:of of:
MATCH : pattern:The mayor of of simpleton
regex: b(w+) 1b
:Never Never:
:Never Never:
MATCH : pattern:Never Never Never Never Never
regex: b(w+) 1b
NO MATCH: pattern:222 2222
regex: b(w+) 1b
NO MATCH: pattern:sara sarah
regex: b(w+) 1b
NO MATCH: pattern:Faster pussycat kill, kill
regex: b(w+) 1b
NO MATCH: pattern:. .
regex: b(w+) 1b
This was an example of how to find duplication in Strings in Java.
