bug fix of correct answer index

Author: yarivtal

java/spring_quiz/.gitignore

@@ -3,3 +3,9 @@
 
 # Ignore Gradle build output directory
 build
+
+# log rolling files, lock file
+*.log.*
+answers.txt
+answers.txt.lck
+

java/spring_quiz/.vscode/launch.json

@@ -4,12 +4,6 @@
     // For more information, visit: https://go.microsoft.com/fwlink/?linkid=830387
     "version": "0.2.0",
     "configurations": [
-        {
-            "type": "java",
-            "name": "Current File",
-            "request": "launch",
-            "mainClass": "${file}"
-        },
         {
             "type": "java",
             "name": "Application",
@@ -20,6 +14,12 @@
             "env": {
                 "JAVA_TOOL_OPTIONS": "-Djava.util.logging.config.file=${workspaceFolder}/logging.properties"
             }
+        },
+        {
+            "type": "java",
+            "name": "Current File",
+            "request": "launch",
+            "mainClass": "${file}"
         }
     ]
 }

java/spring_quiz/src/main/java/com/securefromscratch/quiz/model/QuestionAndAnswers.java

@@ -22,15 +22,20 @@ public record ShuffledAnswers(String[] options, int correctAnswerIdx) { }
     public ShuffledAnswers generateShuffledAnswers() {
         String[] possibleAnswers = Arrays.copyOf(m_wrongAnswerOptions, m_wrongAnswerOptions.length + 1);
         possibleAnswers[m_wrongAnswerOptions.length] = m_correctAnswer;
-        int correctAnswerIdx = secureShuffle(possibleAnswers, m_wrongAnswerOptions.length);
-        return new ShuffledAnswers(possibleAnswers, correctAnswerIdx);
+        secureShuffle(possibleAnswers);
+        for (int i = 0 ; i < possibleAnswers.length ; ++i) {
+            if (possibleAnswers[i].equals(m_correctAnswer)) {
+                return new ShuffledAnswers(possibleAnswers, i);
+            }
+        }
+        return new ShuffledAnswers(possibleAnswers, 0); // should never be reached
     }
 
     public boolean isCorrectAnswer(String a_answer) {
         return a_answer.equals(m_correctAnswer);
     }
 
-    private static int secureShuffle(String[] a_toShuffle, int a_correctAnswerIdx) {
+    private static void secureShuffle(String[] a_toShuffle) {
         SecureRandom random = new SecureRandom();
         for (int i = a_toShuffle.length - 1; i > 0; --i) {
             int toSwapWith = random.nextInt(i + 1);
@@ -39,10 +44,6 @@ private static int secureShuffle(String[] a_toShuffle, int a_correctAnswerIdx) {
             String savedFirstVal = a_toShuffle[toSwapWith];
             a_toShuffle[toSwapWith] = a_toShuffle[i];
             a_toShuffle[i] = savedFirstVal;
-            if (a_correctAnswerIdx == toSwapWith) {
-                a_correctAnswerIdx = i;
-            }
         }
-        return a_correctAnswerIdx;
     }
 }