BAEL-3905 - replacing tokens tests and implementation

core-java-modules/core-java-regex/src/main/java/com/baeldung/replacetokens/ReplacingTokens.java

@@ -0,0 +1,63 @@
+package com.baeldung.replacetokens;
+
+import java.util.function.Function;
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
+
+public class ReplacingTokens {
+    public static final Pattern TITLE_CASE_PATTERN = Pattern.compile("(?<=^|[^A-Za-z])([A-Z][a-z]*)(?=[^A-Za-z]|$)");
+
+    /**
+     * Iterate over the title case tokens in the input and replace them with lowercase
+     * @param original the original string
+     * @return a string with words replaced with their lowercase equivalents
+     */
+    public static String replaceTitleCaseWithLowerCase(String original) {
+        int lastIndex = 0;
+        StringBuilder output = new StringBuilder();
+        Matcher matcher = TITLE_CASE_PATTERN.matcher(original);
+        while (matcher.find()) {
+            output.append(original, lastIndex, matcher.start())
+                    .append(convert(matcher.group(1)));
+
+            lastIndex = matcher.end();
+        }
+        if (lastIndex < original.length()) {
+            output.append(original, lastIndex, original.length());
+        }
+        return output.toString();
+    }
+
+    /**
+     * Convert a token found into its desired lowercase
+     * @param token the token to convert
+     * @return the converted token
+     */
+    private static String convert(String token) {
+        return token.toLowerCase();
+    }
+
+    /**
+     * Replace all the tokens in an input using the algorithm provided for each
+     * @param original original string
+     * @param tokenPattern the pattern to match with
+     * @param converter the conversion to apply
+     * @return the substituted string
+     */
+    public static String replaceTokens(String original, Pattern tokenPattern,
+                                       Function<Matcher, String> converter) {
+        int lastIndex = 0;
+        StringBuilder output = new StringBuilder();
+        Matcher matcher = tokenPattern.matcher(original);
+        while (matcher.find()) {
+            output.append(original, lastIndex, matcher.start())
+                    .append(converter.apply(matcher));
+
+            lastIndex = matcher.end();
+        }
+        if (lastIndex < original.length()) {
+            output.append(original, lastIndex, original.length());
+        }
+        return output.toString();
+    }
+}