Better atomic config saving

Pass the `ATOMIC_MOVE` flag to signal that we want the final file renaming to
be atomic if possible. Catch the exception that occurs when it's not supported
on the OS or drive, and fall back to not using that flag.

Java/Debugger/src/edu/umich/soar/debugger/general/AppProperties.java

@@ -12,10 +12,14 @@
 import java.io.FileInputStream;
 import java.io.FileNotFoundException;
 import java.io.FileOutputStream;
+import java.nio.file.AtomicMoveNotSupportedException;
 import java.nio.file.Files;
 import java.nio.file.Path;
 import java.nio.file.Paths;
-import java.nio.file.StandardCopyOption;
+import java.util.logging.Logger;
+
+import static java.nio.file.StandardCopyOption.ATOMIC_MOVE;
+import static java.nio.file.StandardCopyOption.REPLACE_EXISTING;
 
 public class AppProperties extends java.util.Properties
 {
@@ -27,6 +31,8 @@ public class AppProperties extends java.util.Properties
 
     protected final String kVersion = "Version";
 
+    private static final Logger LOGGER = Logger.getLogger(AppProperties.class.getName());
+
     /**
      * The filename is just a filename--not a full path. The file is stored
      * relative to the user's home directory on Unix or the user's application
@@ -146,7 +152,6 @@ public boolean Load(String version) throws java.io.IOException
             // File doesn't exist. No properties to load, so we're done.
             return false;
         }
-
     }
 
     public void Save() throws java.io.IOException {
@@ -162,8 +167,13 @@ public void Save() throws java.io.IOException {
         try (FileOutputStream output = new FileOutputStream(tempPath.toFile())) {
             this.store(output, this.m_Header);
         }
-
-        Files.move(tempPath, finalPath, StandardCopyOption.REPLACE_EXISTING);
+        try {
+            Files.move(tempPath, finalPath, REPLACE_EXISTING, ATOMIC_MOVE);
+        } catch (AtomicMoveNotSupportedException e) {
+            LOGGER.warning(
+                "Cannot write " + finalPath + " atomically (" + e.getMessage() + "); falling back to non-atomic write");
+            Files.move(tempPath, finalPath, REPLACE_EXISTING);
+        }
     }
 
     public String getFilename()