Run-length encoding: Difference between revisions
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=={{header|Java}}==
This can be achieved using regular expression capturing
<syntaxhighlight lang="java">
import java.util.regex.Matcher;
import java.util.regex.Pattern;
</syntaxhighlight>
<syntaxhighlight lang="java">
String encode(String string) {
Pattern pattern = Pattern.compile("(.)\\1*");
Matcher matcher = pattern.matcher(string);
StringBuilder encoded = new StringBuilder();
while (matcher.find()) {
encoded.append(matcher.group().length());
encoded.append(matcher.group().charAt(0));
}
return encoded.toString();
}
</syntaxhighlight>
<syntaxhighlight lang="java">
String decode(String string) {
Pattern pattern = Pattern.compile("(\\d+)(.)");
Matcher matcher = pattern.matcher(string);
StringBuilder decoded = new StringBuilder();
int count;
while (matcher.find()) {
count = Integer.parseInt(matcher.group(1));
decoded.append(matcher.group(2).repeat(count));
}
return decoded.toString();
}
</syntaxhighlight>
<pre>
string = WWWWWWWWWWWWBWWWWWWWWWWWWBBBWWWWWWWWWWWWWWWWWWWWWWWWBWWWWWWWWWWWWWW
encoded = 12W1B12W3B24W1B14W
decoded = WWWWWWWWWWWWBWWWWWWWWWWWWBBBWWWWWWWWWWWWWWWWWWWWWWWWBWWWWWWWWWWWWWW
string.equals(decoded) = true
string = https://www.rosettacode.org/
encoded = 1h2t1p1s1:2/3w1.1r1o1s1e2t1a1c1o1d1e1.1o1r1g1/
decoded = https://www.rosettacode.org/
string.equals(decoded) = true
</pre>
<br />
An alternate demonstration
<syntaxhighlight lang="java">import java.util.regex.Matcher;
import java.util.regex.Pattern;
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