changed it so the user data in user.json is appended and not overwritten

src/main/java/SignUp.java

@@ -1,9 +1,18 @@
 import com.google.gson.Gson;
+import com.google.gson.GsonBuilder;
+import com.google.gson.reflect.TypeToken;
+
+import java.io.*;
+import java.lang.reflect.Type;
+import java.util.ArrayList;
+import java.util.List;
+
 import java.io.FileWriter;
 import java.io.IOException;
+
 import java.util.UUID;
 
-public class SignUp {
+class SignUp {
 	private String id;
     private String userName;
     private String password;
@@ -65,20 +74,38 @@ public class SignUp {
     
  // Function to save to JSON file, replace with database call later
     public void saveToJsonFile(String filename) {
+    	List<SignUp> userList = readUserListFromJsonFile(filename);
+        userList.add(this);
+        
         try (FileWriter fileWriter = new FileWriter(filename)) {
-            Gson gson = new Gson();
-            gson.toJson(this, fileWriter);
-            System.out.println("User information saved to " + filename);
+        	Gson gson = new GsonBuilder().setPrettyPrinting().create();
+            gson.toJson(userList, fileWriter);
+            System.out.println("User information appended to " + filename);
         } catch (IOException e) {
         System.out.println("Error occurred while saving user information to JSON file: " + e.getMessage());
         }
     }
+    
+ // Function to read user information from a JSON file
+    public static List<SignUp> readUserListFromJsonFile(String filename) {
+        List<SignUp> userList = new ArrayList<>();
+        try (Reader reader = new FileReader(filename)) {
+            Type userListType = new TypeToken<List<SignUp>>() {}.getType();
+            Gson gson = new Gson();
+            userList = gson.fromJson(reader, userListType);
+        } catch (FileNotFoundException e) {
+            // File does not exist yet, so return an empty list
+        } catch (IOException e) {
+            System.out.println("Error occurred while reading user information from JSON file: " + e.getMessage());
+        }
+        return userList;
+    }
 
     public static void main(String[] args) {
         try {
             // Example usage
         	UUID randomUUID = UUID.randomUUID();
-            SignUp user = createUser(randomUUID.toString(), "Test User", "TestPasswort", "01.01.1900");
+        	SignUp user = createUser(randomUUID.toString(), "Another Test User", "TestPasswort123", "01.01.2000");
 
             // Example of accessing properties
             System.out.println("UserID: " + user.getId());

user.json

@@ -1 +1,26 @@
-{"id":"48728bbb-b924-48ce-aac0-3e38d6c7878e","userName":"Test User","password":"TestPasswort","birthday":"01.01.1900"}
+[
+  {
+    "id": "48728bbb-b924-48ce-aac0-3e38d6c7878e",
+    "userName": "Test User",
+    "password": "TestPasswort",
+    "birthday": "01.01.1900"
+  },
+  {
+    "id": "bacd2bf9-9486-4cc3-92fe-9a24b5cf47a4",
+    "userName": "Test User",
+    "password": "TestPasswort",
+    "birthday": "01.01.1900"
+  },
+  {
+    "id": "15474da8-c2cd-4c1c-ba57-cd1b8657140e",
+    "userName": "Test User",
+    "password": "TestPasswort",
+    "birthday": "01.01.1900"
+  },
+  {
+    "id": "be83e49a-bb17-4be2-a50f-0b846d7de3ea",
+    "userName": "Another Test User",
+    "password": "TestPasswort123",
+    "birthday": "01.01.2000"
+  }
+]