Document FileManager

src/FileManager.java

@@ -1,20 +1,17 @@
+// Eric Li, Charlie Zhao, ICS4U, Finished 2022-06-17
 //This class allows us to input and output flies useful for
-//Inputing levels and making save data.
+// inputting levels and making save data.
 import java.io.*;
 import java.util.ArrayList;
 import java.util.List;
 import java.util.Scanner;
 
 // TODO: close scanner etc after use
-public class FileManager {
-    public static void writeFile(String fileLocation, String writeString) throws IOException {
-        File newFile = new File(fileLocation);
-        FileWriter fileWriter = new FileWriter(newFile);
-        fileWriter.write(writeString);
-        fileWriter.close();
-    }
+public final class FileManager {
 
     // will create file if it doesn't exist
+    // does not include robust file closing as readFile is simpler and less likely to fail during reading
+    // additionally, even failing won't affect readFile as reading is a non-exclusive action (a lock will not prevent it)
     public static String readFile(String fileLocation) throws IOException {
         File newFile = new File(fileLocation);
         if (newFile.createNewFile()) {
@@ -28,35 +25,48 @@ public class FileManager {
         }
     }
 
+    // includes robust file closing
     public static Object readObjectFromFile(String fileLocation, List<String> allowedObject) throws IOException, ClassNotFoundException {
         ObjectInputStream objectStream;
         Object o;
         FileInputStream fileStream = new FileInputStream(fileLocation);
+        // if the allowedObject list is not "Any", ensure that the objects loaded are in the list
+        // this can help mitigate the security risk with deserializing untrusted files
         if (!allowedObject.contains("Any")) {
             objectStream = new SafeObjectInputStream(fileStream, allowedObject);
         } else {
+            // otherwise, use the unsafe class
             objectStream = new ObjectInputStream(fileStream);
         }
         try {
             o = objectStream.readObject();
+            return o;
         } catch (Exception e) {
             // please note that the broad exception Exception was used here
             // as in the event of any exception, the object should still be closed
-            // additionally, the exception is reraised, so no information is lost from being too coarse
+            // additionally, the exception is re-raised, so no information is lost from being too coarse
             objectStream.close();
             fileStream.close();
             throw e;
-        }
+        } finally {
             objectStream.close();
             fileStream.close();
-        return o;
+        }
     }
 
+    // includes robust file closing
     public static void writeObjectToFile(String fileLocation, Object o) throws IOException {
         FileOutputStream fileStream = new FileOutputStream(fileLocation);
         ObjectOutputStream objectStream = new ObjectOutputStream(fileStream);
+        try {
             objectStream.writeObject(o);
+        // please note that a less broad exception was used here compared to readObject, as the only "safe" exception to raise in this circumstance is IOException
+        } catch (IOException e) {
+            throw new RuntimeException(e);
+        } finally {
+            // close resources used even if writing caused an error
             objectStream.close();
             fileStream.close();
         }
     }
+}