Shrink a string

Chapter10/StringShrinker/pom.xml

@@ -0,0 +1,14 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+    <groupId>coding.challenge</groupId>
+    <artifactId>StringShrinker</artifactId>
+    <version>1.0</version>
+    <packaging>jar</packaging>
+    <properties>
+        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
+        <maven.compiler.source>13</maven.compiler.source>
+        <maven.compiler.target>13</maven.compiler.target>
+    </properties>
+    <name>StringShrinker</name>
+</project>

Chapter10/StringShrinker/src/main/java/coding/challenge/Main.java

@@ -0,0 +1,13 @@
+package coding.challenge;
+
+public class Main {
+
+    public static void main(String[] args) {
+
+        String str = "abbb vvvv s rttt rr eeee f";        
+
+        System.out.println("Initial: " + str);                
+        System.out.println("Result : " + Strings.shrink(str));                
+    }
+
+}

Chapter10/StringShrinker/src/main/java/coding/challenge/Strings.java

@@ -0,0 +1,48 @@
+package coding.challenge;
+
+public final class Strings {
+
+    private Strings() {
+        throw new AssertionError("Cannot be instantiated");
+    }
+
+    public static String shrink(String str) {
+
+        if (str == null || str.isBlank()) {
+            return "";
+        }
+
+        StringBuilder result = new StringBuilder();
+
+        int count = 0;
+        for (int i = 0; i < str.length(); i++) {
+
+            count++;
+
+            // we don't count whitespaces, we just copy them
+            if (!Character.isWhitespace(str.charAt(i))) {
+
+                // if there are no more characters or the next character 
+                // is different from the counted one
+                if ((i + 1) >= str.length()
+                        || str.charAt(i) != str.charAt(i + 1)) {
+
+                    // append to the final result the counted character
+                    // and number of consecutive occurrences
+                    result.append(str.charAt(i))
+                            .append(count);
+
+                    // reset the counter since this sequence was appended to the result
+                    count = 0;
+                }
+            } else {
+                result.append(str.charAt(i));
+                count = 0;
+            }
+        }
+
+        // return the result only if it is shorter than the given string
+        return result.length() > str.length()
+                ? str : result.toString();
+    }
+}