Complete ThemeUtils#isThemeExist

src/main/java/cc/ryanc/halo/utils/ThemeUtils.java

@@ -184,6 +184,22 @@ public class ThemeUtils {
         return result;
     }
 
+    /**
+     * Judging whether theme exists under template path
+     *
+     * @param theme theme name
+     * @return boolean
+     * @throws FileNotFoundException FileNotFoundException
+     */
+    public static boolean isThemeExist(String theme) throws FileNotFoundException {
+        boolean result = false;
+        File file = new File(getThemesPath(theme), theme);
+        if (file.exists()) {
+            result = true;
+        }
+        return result;
+    }
+
     /**
      * Judging whether the theme is a internal theme or not
      *