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1.20.4 Lightweight Minecraft server
package net.minestom.server.utils;
import org.jetbrains.annotations.NotNull;
public class StringUtils {
public static final String SPACE = " ";
public static final char SPACE_CHAR = ' ';
public static int countMatches(@NotNull final CharSequence str, final char ch) {
if (str.length() == 0) {
return 0;
}
int count = 0;
// We could also call str.toCharArray() for faster look ups but that would generate more garbage.
for (int i = 0; i < str.length(); i++) {
if (ch == str.charAt(i)) {
count++;
}
}
return count;
}
/**
* Applies the Jaro-Winkler distance algorithm to the given strings, providing information about the
* similarity of them.
*
* @param s1 The first string that gets compared. May be null or empty.
* @param s2 The second string that gets compared. May be null or empty.
* @return The Jaro-Winkler score (between 0.0 and 1.0), with a higher value indicating larger similarity.
* @author Thomas Trojer [email protected]
*/
public static double jaroWinklerScore(final String s1, final String s2) {
// lowest score on empty strings
if (s1 == null || s2 == null || s1.isEmpty() || s2.isEmpty()) {
return 0;
}
// highest score on equal strings
if (s1.equals(s2)) {
return 1;
}
// some score on different strings
int prefixMatch = 0; // exact prefix matches
int matches = 0; // matches (including prefix and ones requiring transpostion)
int transpositions = 0; // matching characters that are not aligned but close together
int maxLength = Math.max(s1.length(), s2.length());
int maxMatchDistance = Math.max((int) Math.floor(maxLength / 2.0) - 1, 0); // look-ahead/-behind to limit transposed matches
// comparison
final String shorter = s1.length() < s2.length() ? s1 : s2;
final String longer = s1.length() >= s2.length() ? s1 : s2;
for (int i = 0; i < shorter.length(); i++) {
// check for exact matches
boolean match = shorter.charAt(i) == longer.charAt(i);
if (match) {
if (i < 4) {
// prefix match (of at most 4 characters, as described by the algorithm)
prefixMatch++;
}
matches++;
continue;
}
// check fro transposed matches
for (int j = Math.max(i - maxMatchDistance, 0); j < Math.min(i + maxMatchDistance, longer.length()); j++) {
if (i == j) {
// case already covered
continue;
}
// transposition required to match?
match = shorter.charAt(i) == longer.charAt(j);
if (match) {
transpositions++;
break;
}
}
}
// any matching characters?
if (matches == 0) {
return 0;
}
// modify transpositions (according to the algorithm)
transpositions = (int) (transpositions / 2.0);
// non prefix-boosted score
double score = 0.3334 * (matches / (double) longer.length() + matches / (double) shorter.length() + (matches - transpositions)
/ (double) matches);
if (score < 0.7) {
return score;
}
// we already have a good match, hence we boost the score proportional to the common prefix
return score + prefixMatch * 0.1 * (1.0 - score);
}
public static String unescapeJavaString(String st) {
StringBuilder sb = new StringBuilder(st.length());
for (int i = 0; i < st.length(); i++) {
char ch = st.charAt(i);
if (ch == '\\') {
char nextChar = (i == st.length() - 1) ? '\\' : st
.charAt(i + 1);
// Octal escape?
if (nextChar >= '0' && nextChar <= '7') {
String code = "" + nextChar;
i++;
if ((i < st.length() - 1) && st.charAt(i + 1) >= '0'
&& st.charAt(i + 1) <= '7') {
code += st.charAt(i + 1);
i++;
if ((i < st.length() - 1) && st.charAt(i + 1) >= '0'
&& st.charAt(i + 1) <= '7') {
code += st.charAt(i + 1);
i++;
}
}
sb.append((char) Integer.parseInt(code, 8));
continue;
}
switch (nextChar) {
case '\\' -> ch = '\\';
case 'b' -> ch = '\b';
case 'f' -> ch = '\f';
case 'n' -> ch = '\n';
case 'r' -> ch = '\r';
case 't' -> ch = '\t';
case '\"' -> ch = '\"';
case '\'' -> ch = '\'';
// Hex Unicode: u????
case 'u' -> {
if (i >= st.length() - 5) {
ch = 'u';
break;
}
int code = Integer.parseInt(
"" + st.charAt(i + 2) + st.charAt(i + 3)
+ st.charAt(i + 4) + st.charAt(i + 5), 16);
sb.append(Character.toChars(code));
i += 5;
continue;
}
}
i++;
}
sb.append(ch);
}
return sb.toString();
}
}