Day 1 implementation in Java - bugfix

java/README.md

@@ -0,0 +1,7 @@
+### How to run?
+
+You need to have your JDK installed. I'll be using JDK-23.
+
+Run from IDE directly, as JAR files have not yet been created.
+
+Different problems are in different folders. Generally a variable contains the value that controlls whether the first sub-problem is executed or the second.  

java/src/main/java/day1/Main.java

@@ -2,12 +2,25 @@ package day1;
 
 import util.FileReader;
 
+import java.util.ArrayList;
+import java.util.HashMap;
 import java.util.List;
 import java.util.stream.Collectors;
 
 public class Main {
     // Part 1 one of the problem has this flag set to false, while part 2 has it set to true
     private static final boolean IS_NUMBER_SPELLING_ENABLED = true;
+    private static final HashMap<String, Character> SPELLED_NUMBERS = new HashMap<String, Character>() {{
+        put("one", '1');
+        put("two", '2');
+        put("three", '3');
+        put("four", '4');
+        put("five", '5');
+        put("six", '6');
+        put("seven", '7');
+        put("eight", '8');
+        put("nine", '9');
+    }};
 
     public static void main(String[] args) {
         String inputFilePath = System.getProperty("user.dir") + "\\java\\src\\main\\java\\day1\\input.txt";
@@ -36,23 +49,24 @@ public class Main {
     }
 
     private static String replaceSpelledDigits(String string) {
-        return string
-            .replaceAll("oneight", "18")
-            .replaceAll("threeight", "38")
-            .replaceAll("fiveight", "58")
-            .replaceAll("nineight", "98")
-            .replaceAll("twone", "21")
-            .replaceAll("eightwo", "82")
-            .replaceAll("eighthree", "83")
-            .replaceAll("one", "1")
-            .replaceAll("two", "2")
-            .replaceAll("three", "3")
-            .replaceAll("four", "4")
-            .replaceAll("five", "5")
-            .replaceAll("six", "6")
-            .replaceAll("seven", "7")
-            .replaceAll("eight", "8")
-            .replaceAll("nine", "9");
+        StringBuilder newStringBuilder = new StringBuilder(string);
+        SPELLED_NUMBERS.keySet().stream()
+            .filter(string::contains)
+            .forEach(number -> getIndexesOfAllSubstringOccurrences(string, number)
+                .forEach(index -> newStringBuilder.setCharAt(index, SPELLED_NUMBERS.get(number)))
+            );
+
+        return newStringBuilder.toString();
+    }
+
+    private static List<Integer> getIndexesOfAllSubstringOccurrences(String string, String substring) {
+        List<Integer> indexes = new ArrayList<>();
+        int index = string.indexOf(substring);
+        while (index >= 0) {
+            indexes.add(index);
+            index = string.indexOf(substring, index + 1);
+        }
+        return indexes;
     }
 }