diff --git a/README.md b/README.md
index 3bcf2be2..6b3894b5 100644
--- a/README.md
+++ b/README.md
@@ -3,6 +3,7 @@
 [![Build Status](https://api.travis-ci.org/shadowsocks/shadowsocks-android.svg)](https://travis-ci.org/shadowsocks/shadowsocks-android)
 [![API](https://img.shields.io/badge/API-21%2B-brightgreen.svg?style=flat)](https://android-arsenal.com/api?level=21)
 [![Releases](https://img.shields.io/github/downloads/shadowsocks/shadowsocks-android/total.svg)](https://github.com/shadowsocks/shadowsocks-android/releases)
+[![Codacy Badge](https://api.codacy.com/project/badge/Grade/1a21d48d466644cdbcb57a1889abea5b)](https://www.codacy.com/app/shadowsocks/shadowsocks-android?utm_source=github.com&utm_medium=referral&utm_content=shadowsocks/shadowsocks-android&utm_campaign=Badge_Grade)
 [![License: GPL v3](https://img.shields.io/badge/License-GPL%20v3-blue.svg)](https://www.gnu.org/licenses/gpl-3.0)
 
 A [shadowsocks](http://shadowsocks.org) client for Android, written in Kotlin.  
diff --git a/core/gfwlist/gen.py b/core/gfwlist/gen.py
index 22ab9048..ddc250ad 100644
--- a/core/gfwlist/gen.py
+++ b/core/gfwlist/gen.py
@@ -1,8 +1,6 @@
 #!/usr/bin/python
 # -*- encoding: utf8 -*-
 
-import itertools
-import math
 import sys
 
 import IPy
diff --git a/detekt.yml b/detekt.yml
index c8c71bcb..ef1033e1 100644
--- a/detekt.yml
+++ b/detekt.yml
@@ -28,8 +28,7 @@ complexity:
     threshold: 5
     ignoreDefaultParameters: true
   MethodOverloading:
-    active: true
-    threshold: 5
+    active: false
   NestedBlockDepth:
     active: true
     threshold: 3
diff --git a/mobile/src/main/java/com/github/shadowsocks/AppManager.kt b/mobile/src/main/java/com/github/shadowsocks/AppManager.kt
index 9c6c1d5f..598bff2b 100644
--- a/mobile/src/main/java/com/github/shadowsocks/AppManager.kt
+++ b/mobile/src/main/java/com/github/shadowsocks/AppManager.kt
@@ -44,7 +44,6 @@ import android.support.v7.widget.Toolbar
 import android.view.*
 import android.widget.ImageView
 import android.widget.Switch
-import android.widget.Toast
 import com.futuremind.recyclerviewfastscroll.FastScroller
 import com.futuremind.recyclerviewfastscroll.SectionTitleProvider
 import com.github.shadowsocks.App.Companion.app
@@ -264,11 +263,9 @@ class AppManager : AppCompatActivity(), Toolbar.OnMenuItemClickListener {
         return false
     }
 
-    override fun onKeyUp(keyCode: Int, event: KeyEvent?): Boolean {
-        return if (keyCode == KeyEvent.KEYCODE_MENU)
-            if (toolbar.isOverflowMenuShowing) toolbar.hideOverflowMenu() else toolbar.showOverflowMenu()
-        else super.onKeyUp(keyCode, event)
-    }
+    override fun onKeyUp(keyCode: Int, event: KeyEvent?) = if (keyCode == KeyEvent.KEYCODE_MENU)
+        if (toolbar.isOverflowMenuShowing) toolbar.hideOverflowMenu() else toolbar.showOverflowMenu()
+    else super.onKeyUp(keyCode, event)
 
     override fun onDestroy() {
         instance = null
diff --git a/mobile/src/main/java/com/github/shadowsocks/GlobalSettingsPreferenceFragment.kt b/mobile/src/main/java/com/github/shadowsocks/GlobalSettingsPreferenceFragment.kt
index 301490a2..fae6cc75 100644
--- a/mobile/src/main/java/com/github/shadowsocks/GlobalSettingsPreferenceFragment.kt
+++ b/mobile/src/main/java/com/github/shadowsocks/GlobalSettingsPreferenceFragment.kt
@@ -26,7 +26,6 @@ import android.os.Bundle
 import android.support.design.widget.Snackbar
 import android.support.v14.preference.SwitchPreference
 import android.support.v7.preference.Preference
-import com.github.shadowsocks.App.Companion.app
 import com.github.shadowsocks.bg.BaseService
 import com.github.shadowsocks.preference.DataStore
 import com.github.shadowsocks.utils.DirectBoot
diff --git a/mobile/src/main/java/com/github/shadowsocks/MainActivity.kt b/mobile/src/main/java/com/github/shadowsocks/MainActivity.kt
index d8842a99..c027ecbf 100644
--- a/mobile/src/main/java/com/github/shadowsocks/MainActivity.kt
+++ b/mobile/src/main/java/com/github/shadowsocks/MainActivity.kt
@@ -62,6 +62,7 @@ import com.mikepenz.materialdrawer.Drawer
 import com.mikepenz.materialdrawer.DrawerBuilder
 import com.mikepenz.materialdrawer.model.PrimaryDrawerItem
 import com.mikepenz.materialdrawer.model.interfaces.IDrawerItem
+import java.io.IOException
 import java.net.HttpURLConnection
 import java.net.InetSocketAddress
 import java.net.Proxy
@@ -178,8 +179,8 @@ class MainActivity : AppCompatActivity(), ShadowsocksConnection.Interface, Drawe
             val elapsed = SystemClock.elapsedRealtime() - start
             if (code == 204 || code == 200 && conn.responseLength == 0L)
                 Pair(true, getString(R.string.connection_test_available, elapsed))
-            else throw Exception(getString(R.string.connection_test_error_status_code, code))
-        } catch (e: Exception) {
+            else throw IOException(getString(R.string.connection_test_error_status_code, code))
+        } catch (e: IOException) {
             Pair(false, getString(R.string.connection_test_error, e.message))
         } finally {
             conn.disconnect()
diff --git a/mobile/src/main/java/com/github/shadowsocks/ProfileConfigFragment.kt b/mobile/src/main/java/com/github/shadowsocks/ProfileConfigFragment.kt
index 98817951..f71be5d9 100644
--- a/mobile/src/main/java/com/github/shadowsocks/ProfileConfigFragment.kt
+++ b/mobile/src/main/java/com/github/shadowsocks/ProfileConfigFragment.kt
@@ -179,27 +179,25 @@ class ProfileConfigFragment : PreferenceFragmentCompatDividers(), Toolbar.OnMenu
         } else super.onActivityResult(requestCode, resultCode, data)
     }
 
-    override fun onMenuItemClick(item: MenuItem): Boolean {
-        return when (item.itemId) {
-            R.id.action_delete -> {
-                val activity = activity!!
-                AlertDialog.Builder(activity)
-                        .setTitle(R.string.delete_confirm_prompt)
-                        .setPositiveButton(R.string.yes, { _, _ ->
-                            ProfileManager.delProfile(profile.id)
-                            activity.finish()
-                        })
-                        .setNegativeButton(R.string.no, null)
-                        .create()
-                        .show()
-                true
-            }
-            R.id.action_apply -> {
-                saveAndExit()
-                true
-            }
-            else -> false
+    override fun onMenuItemClick(item: MenuItem) = when (item.itemId) {
+        R.id.action_delete -> {
+            val activity = activity!!
+            AlertDialog.Builder(activity)
+                    .setTitle(R.string.delete_confirm_prompt)
+                    .setPositiveButton(R.string.yes, { _, _ ->
+                        ProfileManager.delProfile(profile.id)
+                        activity.finish()
+                    })
+                    .setNegativeButton(R.string.no, null)
+                    .create()
+                    .show()
+            true
         }
+        R.id.action_apply -> {
+            saveAndExit()
+            true
+        }
+        else -> false
     }
 
     override fun onDestroy() {
diff --git a/mobile/src/main/java/com/github/shadowsocks/ProfilesFragment.kt b/mobile/src/main/java/com/github/shadowsocks/ProfilesFragment.kt
index dddf5383..7a62830c 100644
--- a/mobile/src/main/java/com/github/shadowsocks/ProfilesFragment.kt
+++ b/mobile/src/main/java/com/github/shadowsocks/ProfilesFragment.kt
@@ -37,7 +37,6 @@ import android.view.*
 import android.widget.ImageView
 import android.widget.LinearLayout
 import android.widget.TextView
-import android.widget.Toast
 import com.github.shadowsocks.App.Companion.app
 import com.github.shadowsocks.bg.BaseService
 import com.github.shadowsocks.bg.TrafficMonitor
@@ -374,9 +373,7 @@ class ProfilesFragment : ToolbarFragment(), Toolbar.OnMenuItemClickListener {
                                 Snackbar.LENGTH_LONG).show()
                         return true
                     }
-                } catch (exc: Exception) {
-                    app.track(exc)
-                }
+                } catch (_: IndexOutOfBoundsException) { }
                 Snackbar.make(activity!!.findViewById(R.id.snackbar), R.string.action_import_err, Snackbar.LENGTH_LONG)
                         .show()
                 true
diff --git a/mobile/src/main/java/com/github/shadowsocks/ScannerActivity.kt b/mobile/src/main/java/com/github/shadowsocks/ScannerActivity.kt
index d94ca422..11a96842 100644
--- a/mobile/src/main/java/com/github/shadowsocks/ScannerActivity.kt
+++ b/mobile/src/main/java/com/github/shadowsocks/ScannerActivity.kt
@@ -139,31 +139,29 @@ class ScannerActivity : AppCompatActivity(), ZXingScannerView.ResultHandler, Too
             .putExtra(Intent.EXTRA_ALLOW_MULTIPLE, true), if (manual) REQUEST_IMPORT else REQUEST_IMPORT_OR_FINISH)
     override fun onActivityResult(requestCode: Int, resultCode: Int, data: Intent?) {
         when (requestCode) {
-            REQUEST_IMPORT, REQUEST_IMPORT_OR_FINISH -> {
-                if (resultCode == Activity.RESULT_OK) {
-                    var list = listOfNotNull(data?.data)
-                    val clipData = data?.clipData
-                    if (clipData != null) list += (0 until clipData.itemCount).map { clipData.getItemAt(it).uri }
-                    val resolver = contentResolver
-                    val reader = MultiFormatReader()
-                    var success = false
-                    for (uri in list) try {
-                        val bitmap = BitmapFactory.decodeStream(resolver.openInputStream(uri))
-                        val pixels = IntArray(bitmap.width * bitmap.height)
-                        bitmap.getPixels(pixels, 0, bitmap.width, 0, 0, bitmap.width, bitmap.height)
-                        Profile.findAll(reader.decode(BinaryBitmap(HybridBinarizer(
-                                RGBLuminanceSource(bitmap.width, bitmap.height, pixels)))).text).forEach {
-                            ProfileManager.createProfile(it)
-                            success = true
-                        }
-                    } catch (e: Exception) {
-                        app.track(e)
+            REQUEST_IMPORT, REQUEST_IMPORT_OR_FINISH -> if (resultCode == Activity.RESULT_OK) {
+                var list = listOfNotNull(data?.data)
+                val clipData = data?.clipData
+                if (clipData != null) list += (0 until clipData.itemCount).map { clipData.getItemAt(it).uri }
+                val resolver = contentResolver
+                val reader = MultiFormatReader()
+                var success = false
+                for (uri in list) try {
+                    val bitmap = BitmapFactory.decodeStream(resolver.openInputStream(uri))
+                    val pixels = IntArray(bitmap.width * bitmap.height)
+                    bitmap.getPixels(pixels, 0, bitmap.width, 0, 0, bitmap.width, bitmap.height)
+                    Profile.findAll(reader.decode(BinaryBitmap(HybridBinarizer(
+                            RGBLuminanceSource(bitmap.width, bitmap.height, pixels)))).text).forEach {
+                        ProfileManager.createProfile(it)
+                        success = true
                     }
-                    Toast.makeText(this, if (success) R.string.action_import_msg else R.string.action_import_err,
-                            Toast.LENGTH_SHORT).show()
-                    finish()
-                } else if (requestCode == REQUEST_IMPORT_OR_FINISH) finish()
-            }
+                } catch (e: Exception) {
+                    app.track(e)
+                }
+                Toast.makeText(this, if (success) R.string.action_import_msg else R.string.action_import_err,
+                        Toast.LENGTH_SHORT).show()
+                finish()
+            } else if (requestCode == REQUEST_IMPORT_OR_FINISH) finish()
             else -> super.onActivityResult(requestCode, resultCode, data)
         }
     }
diff --git a/mobile/src/main/java/com/github/shadowsocks/acl/CustomRulesFragment.kt b/mobile/src/main/java/com/github/shadowsocks/acl/CustomRulesFragment.kt
index 631c9ebe..0c5065f5 100644
--- a/mobile/src/main/java/com/github/shadowsocks/acl/CustomRulesFragment.kt
+++ b/mobile/src/main/java/com/github/shadowsocks/acl/CustomRulesFragment.kt
@@ -124,7 +124,7 @@ class CustomRulesFragment : ToolbarFragment(), Toolbar.OnMenuItemClickListener,
         override fun beforeTextChanged(s: CharSequence?, start: Int, count: Int, after: Int) { }
         override fun onTextChanged(s: CharSequence?, start: Int, before: Int, count: Int) { }
         override fun afterTextChanged(s: Editable) = validate(value = s)
-        override fun onNothingSelected(parent: AdapterView<*>?) = throw IllegalStateException()
+        override fun onNothingSelected(parent: AdapterView<*>?) = check(false)
         override fun onItemSelected(parent: AdapterView<*>?, view: View?, position: Int, id: Long) = validate(position)
 
         private fun validate(template: Int = templateSelector.selectedItemPosition, value: Editable = editText.text) {
@@ -228,16 +228,14 @@ class CustomRulesFragment : ToolbarFragment(), Toolbar.OnMenuItemClickListener,
         override fun getItemCount(): Int = acl.subnets.size() + acl.hostnames.size() + acl.urls.size()
         override fun getSectionTitle(i: Int): String {
             val j = i - acl.subnets.size()
-            return try {
-                (if (j < 0) acl.subnets[i].address.hostAddress.substring(0, 1) else {
-                    val k = j - acl.hostnames.size()
-                    if (k < 0) {
-                        val hostname = acl.hostnames[j]
-                        // don't convert IDN yet
-                        PATTERN_DOMAIN.find(hostname)?.value?.replace("\\.", ".") ?: hostname
-                    } else acl.urls[k].host
-                }).substring(0, 1)
-            } catch (_: IndexOutOfBoundsException) { " " }
+            return (if (j < 0) acl.subnets[i].address.hostAddress.substring(0, 1) else {
+                val k = j - acl.hostnames.size()
+                if (k < 0) {
+                    val hostname = acl.hostnames[j]
+                    // don't convert IDN yet
+                    PATTERN_DOMAIN.find(hostname)?.value?.replace("\\.", ".") ?: hostname
+                } else acl.urls[k].host
+            }).firstOrNull()?.toString() ?: " "
         }
 
         private fun apply() {
diff --git a/mobile/src/main/java/com/github/shadowsocks/bg/BaseService.kt b/mobile/src/main/java/com/github/shadowsocks/bg/BaseService.kt
index d9416891..6a703f3c 100644
--- a/mobile/src/main/java/com/github/shadowsocks/bg/BaseService.kt
+++ b/mobile/src/main/java/com/github/shadowsocks/bg/BaseService.kt
@@ -31,7 +31,6 @@ import android.os.RemoteCallbackList
 import android.support.v4.os.UserManagerCompat
 import android.util.Base64
 import android.util.Log
-import android.widget.Toast
 import com.github.shadowsocks.App.Companion.app
 import com.github.shadowsocks.R
 import com.github.shadowsocks.acl.Acl
@@ -146,18 +145,18 @@ object BaseService {
         }
 
         internal fun updateTrafficTotal(tx: Long, rx: Long) {
-            val profile = profile ?: return
-            val p = ProfileManager.getProfile(profile.id) ?: return // profile may have host, etc. modified
-            p.tx += tx
-            p.rx += rx
-            ProfileManager.updateProfile(p)
+            // this.profile may have host, etc. modified and thus a re-fetch is necessary (possible race condition)
+            val profile = ProfileManager.getProfile((profile ?: return).id) ?: return
+            profile.tx += tx
+            profile.rx += rx
+            ProfileManager.updateProfile(profile)
             app.handler.post {
                 if (bandwidthListeners.isNotEmpty()) {
                     val n = callbacks.beginBroadcast()
                     for (i in 0 until n) {
                         try {
                             val item = callbacks.getBroadcastItem(i)
-                            if (bandwidthListeners.contains(item.asBinder())) item.trafficPersisted(p.id)
+                            if (bandwidthListeners.contains(item.asBinder())) item.trafficPersisted(profile.id)
                         } catch (_: Exception) { }  // ignore
                     }
                     callbacks.finishBroadcast()
@@ -182,9 +181,9 @@ object BaseService {
                         .put("plugin_opts", plugin.toString())
             }
             // sensitive Shadowsocks config is stored in
-            val file = File((if (UserManagerCompat.isUserUnlocked(app)) app.filesDir else @TargetApi(24) {
+            val file = File(if (UserManagerCompat.isUserUnlocked(app)) app.filesDir else @TargetApi(24) {
                 app.deviceContext.noBackupFilesDir  // only API 24+ will be in locked state
-            }), CONFIG_FILE)
+            }, CONFIG_FILE)
             shadowsocksConfigFile = file
             file.writeText(config.toString())
             return file
@@ -218,9 +217,9 @@ object BaseService {
                     false
                 } else true
         fun forceLoad() {
-            val p = app.currentProfile
+            val profile = app.currentProfile
                     ?: return stopRunner(true, (this as Context).getString(R.string.profile_empty))
-            if (!checkProfile(p)) return
+            if (!checkProfile(profile)) return
             val s = data.state
             when (s) {
                 STOPPED -> startRunner()
diff --git a/mobile/src/main/java/com/github/shadowsocks/bg/Dns.kt b/mobile/src/main/java/com/github/shadowsocks/bg/Dns.kt
index 56d6840d..9bb52093 100644
--- a/mobile/src/main/java/com/github/shadowsocks/bg/Dns.kt
+++ b/mobile/src/main/java/com/github/shadowsocks/bg/Dns.kt
@@ -24,22 +24,19 @@ import android.util.Log
 import com.github.shadowsocks.App.Companion.app
 import com.github.shadowsocks.BuildConfig
 import org.xbill.DNS.*
-import java.net.Inet6Address
-import java.net.InetAddress
-import java.net.NetworkInterface
-import java.net.UnknownHostException
-import okhttp3.Dns as Okdns
+import java.io.IOException
+import java.net.*
 
 object Dns {
     private const val TAG = "Dns"
 
     private val hasIPv6Support get() = try {
         val result = NetworkInterface.getNetworkInterfaces().asSequence().flatMap { it.inetAddresses.asSequence() }
-                .count { it is Inet6Address && !it.isLoopbackAddress && !it.isLinkLocalAddress } > 0
+                .any { it is Inet6Address && !it.isLoopbackAddress && !it.isLinkLocalAddress }
         if (result && BuildConfig.DEBUG) Log.d(TAG, "IPv6 address detected")
         result
-    } catch (ex: Exception) {
-        Log.e(TAG, "Failed to get interfaces' addresses.")
+    } catch (ex: SocketException) {
+        Log.e(TAG, "Failed to get interfaces' addresses.", ex)
         app.track(ex)
         false
     }
@@ -60,7 +57,7 @@ object Dns {
                     Type.AAAA -> return (r as AAAARecord).address.hostAddress
                 }
             }
-        } catch (_: Exception) { }
+        } catch (_: IOException) { }
         return null
     }
     private fun resolve(host: String): String? = try {
diff --git a/mobile/src/main/java/com/github/shadowsocks/bg/LocalDnsService.kt b/mobile/src/main/java/com/github/shadowsocks/bg/LocalDnsService.kt
index 1d1d9644..ed5925b2 100644
--- a/mobile/src/main/java/com/github/shadowsocks/bg/LocalDnsService.kt
+++ b/mobile/src/main/java/com/github/shadowsocks/bg/LocalDnsService.kt
@@ -20,7 +20,6 @@
 
 package com.github.shadowsocks.bg
 
-import android.content.Context
 import com.github.shadowsocks.App.Companion.app
 import com.github.shadowsocks.acl.Acl
 import com.github.shadowsocks.preference.DataStore
@@ -50,10 +49,10 @@ object LocalDnsService {
             fun makeDns(name: String, address: String, timeout: Int, edns: Boolean = true): JSONObject {
                 val dns = JSONObject()
                 .put("Name", name)
-                .put("Address", (when (address.parseNumericAddress()) {
+                .put("Address", when (address.parseNumericAddress()) {
                     is Inet6Address -> "[$address]"
                     else -> address
-                }))
+                })
                 .put("Timeout", timeout)
                 .put("EDNSClientSubnet", JSONObject().put("Policy", "disable"))
                 if (edns) dns
diff --git a/mobile/src/main/java/com/github/shadowsocks/bg/ProxyService.kt b/mobile/src/main/java/com/github/shadowsocks/bg/ProxyService.kt
index 6f6d0cf1..e1d66872 100644
--- a/mobile/src/main/java/com/github/shadowsocks/bg/ProxyService.kt
+++ b/mobile/src/main/java/com/github/shadowsocks/bg/ProxyService.kt
@@ -23,7 +23,6 @@ package com.github.shadowsocks.bg
 import android.app.Service
 import android.content.Intent
 import android.os.IBinder
-import com.github.shadowsocks.database.Profile
 
 /**
  * Shadowsocks service at its minimum.
diff --git a/mobile/src/main/java/com/github/shadowsocks/bg/TrafficMonitor.kt b/mobile/src/main/java/com/github/shadowsocks/bg/TrafficMonitor.kt
index e04dd3e8..8f99a29b 100644
--- a/mobile/src/main/java/com/github/shadowsocks/bg/TrafficMonitor.kt
+++ b/mobile/src/main/java/com/github/shadowsocks/bg/TrafficMonitor.kt
@@ -44,7 +44,7 @@ object TrafficMonitor {
     private val units = arrayOf("KB", "MB", "GB", "TB", "PB", "EB", "ZB", "YB", "BB", "NB", "DB", "CB")
     private val numberFormat = DecimalFormat("@@@")
     fun formatTraffic(size: Long): String {
-        var n: Double = size.toDouble()
+        var n = size.toDouble()
         var i = -1
         while (n >= 999.5) {
             n /= 1024
diff --git a/mobile/src/main/java/com/github/shadowsocks/bg/TrafficMonitorThread.kt b/mobile/src/main/java/com/github/shadowsocks/bg/TrafficMonitorThread.kt
index 70d1b14d..5d738208 100644
--- a/mobile/src/main/java/com/github/shadowsocks/bg/TrafficMonitorThread.kt
+++ b/mobile/src/main/java/com/github/shadowsocks/bg/TrafficMonitorThread.kt
@@ -38,7 +38,7 @@ class TrafficMonitorThread : LocalSocketListener("TrafficMonitorThread") {
             val stat = ByteBuffer.wrap(buffer).order(ByteOrder.LITTLE_ENDIAN)
             TrafficMonitor.update(stat.getLong(0), stat.getLong(8))
             socket.outputStream.write(0)
-        } catch (e: Exception) {
+        } catch (e: IOException) {
             Log.e(tag, "Error when recv traffic stat", e)
             app.track(e)
         }
diff --git a/mobile/src/main/java/com/github/shadowsocks/bg/VpnService.kt b/mobile/src/main/java/com/github/shadowsocks/bg/VpnService.kt
index c1f9470a..cfba6660 100644
--- a/mobile/src/main/java/com/github/shadowsocks/bg/VpnService.kt
+++ b/mobile/src/main/java/com/github/shadowsocks/bg/VpnService.kt
@@ -38,6 +38,7 @@ import com.github.shadowsocks.utils.Subnet
 import com.github.shadowsocks.utils.parseNumericAddress
 import java.io.File
 import java.io.FileDescriptor
+import java.io.IOException
 import java.lang.reflect.Method
 import java.util.*
 import android.net.VpnService as BaseVpnService
@@ -55,18 +56,24 @@ class VpnService : BaseVpnService(), LocalDnsService.Interface {
         override val socketFile: File = File(app.deviceContext.filesDir, "protect_path")
 
         override fun accept(socket: LocalSocket) {
+            var success = false
             try {
                 socket.inputStream.read()
                 val fds = socket.ancillaryFileDescriptors
                 if (fds.isEmpty()) return
                 val fd = getInt.invoke(fds.first()) as Int
-                val ret = protect(fd)
+                success = protect(fd)
                 JniHelper.close(fd) // Trick to close file decriptor
-                socket.outputStream.write(if (ret) 0 else 1)
             } catch (e: Exception) {
                 Log.e(tag, "Error when protect socket", e)
                 app.track(e)
             }
+            try {
+                socket.outputStream.write(if (success) 0 else 1)
+            } catch (e: IOException) {
+                Log.e(tag, "Error when returning result in protect", e)
+                app.track(e)
+            }
         }
     }
     class NullConnectionException : NullPointerException()
@@ -118,7 +125,7 @@ class VpnService : BaseVpnService(), LocalDnsService.Interface {
         super.startNativeProcesses()
 
         val fd = startVpn()
-        if (!sendFd(fd)) throw Exception("sendFd failed")
+        if (!sendFd(fd)) throw IOException("sendFd failed")
     }
 
     override fun buildAdditionalArguments(cmd: ArrayList<String>): ArrayList<String> {
diff --git a/mobile/src/main/java/com/github/shadowsocks/database/PrivateDatabase.kt b/mobile/src/main/java/com/github/shadowsocks/database/PrivateDatabase.kt
index 61f94686..52215aa4 100644
--- a/mobile/src/main/java/com/github/shadowsocks/database/PrivateDatabase.kt
+++ b/mobile/src/main/java/com/github/shadowsocks/database/PrivateDatabase.kt
@@ -72,10 +72,10 @@ object PrivateDatabase : OrmLiteSqliteOpenHelper(app, Key.DB_PROFILE, null, 25)
                 profileDao.executeRawNoArgs("ALTER TABLE `profile` RENAME TO `tmp`;")
                 TableUtils.createTable(connectionSource, Profile::class.java)
                 profileDao.executeRawNoArgs(
-                        "INSERT INTO `profile`(id, name, host, localPort, remotePort, password, method, route, proxyApps, bypass," +
-                                " udpdns, ipv6, individual) " +
-                                "SELECT id, name, host, localPort, remotePort, password, method, route, 1 - global, bypass, udpdns, ipv6," +
-                                " individual FROM `tmp`;")
+                        "INSERT INTO `profile`(id, name, host, localPort, remotePort, password, method, route," +
+                                " proxyApps, bypass, udpdns, ipv6, individual) " +
+                                "SELECT id, name, host, localPort, remotePort, password, method, route, 1 - global," +
+                                " bypass, udpdns, ipv6, individual FROM `tmp`;")
                 profileDao.executeRawNoArgs("DROP TABLE `tmp`;")
                 profileDao.executeRawNoArgs("COMMIT;")
             } else if (oldVersion < 13) {
diff --git a/mobile/src/main/java/com/github/shadowsocks/database/Profile.kt b/mobile/src/main/java/com/github/shadowsocks/database/Profile.kt
index a756dedd..8e8e2ea1 100644
--- a/mobile/src/main/java/com/github/shadowsocks/database/Profile.kt
+++ b/mobile/src/main/java/com/github/shadowsocks/database/Profile.kt
@@ -36,6 +36,7 @@ import java.util.*
 class Profile : Serializable {
     companion object {
         private const val TAG = "ShadowParser"
+        private const val serialVersionUID = 0L
         private val pattern = """(?i)ss://[-a-zA-Z0-9+&@#/%?=~_|!:,.;\[\]]*[-a-zA-Z0-9+&@#/%=~_|\[\]]""".toRegex()
         private val userInfoPattern = "^(.+?):(.*)$".toRegex()
         private val legacyPattern = "^(.+?):(.*)@(.+?):(\\d+?)$".toRegex()
diff --git a/mobile/src/main/java/com/github/shadowsocks/database/ProfileManager.kt b/mobile/src/main/java/com/github/shadowsocks/database/ProfileManager.kt
index 9ab1c473..15ef7c82 100644
--- a/mobile/src/main/java/com/github/shadowsocks/database/ProfileManager.kt
+++ b/mobile/src/main/java/com/github/shadowsocks/database/ProfileManager.kt
@@ -25,79 +25,69 @@ import com.github.shadowsocks.App.Companion.app
 import com.github.shadowsocks.ProfilesFragment
 import com.github.shadowsocks.preference.DataStore
 import com.github.shadowsocks.utils.DirectBoot
+import java.sql.SQLException
 
+/**
+ * SQLExceptions are not caught (and therefore will cause crash) for insert/update transactions
+ * to ensure we are in a consistent state.
+ */
 object ProfileManager {
     private const val TAG = "ProfileManager"
 
+    @Throws(SQLException::class)
     fun createProfile(p: Profile? = null): Profile {
         val profile = p ?: Profile()
         profile.id = 0
-        try {
-            val oldProfile = app.currentProfile
-            if (oldProfile != null) {
-                // Copy Feature Settings from old profile
-                profile.route = oldProfile.route
-                profile.ipv6 = oldProfile.ipv6
-                profile.proxyApps = oldProfile.proxyApps
-                profile.bypass = oldProfile.bypass
-                profile.individual = oldProfile.individual
-                profile.udpdns = oldProfile.udpdns
-            }
-            val last = PrivateDatabase.profileDao.queryRaw(PrivateDatabase.profileDao.queryBuilder()
-                    .selectRaw("MAX(userOrder)").prepareStatementString()).firstResult
-            if (last != null && last.size == 1 && last[0] != null) profile.userOrder = last[0].toLong() + 1
-            PrivateDatabase.profileDao.createOrUpdate(profile)
-            ProfilesFragment.instance?.profilesAdapter?.add(profile)
-        } catch (ex: Exception) {
-            Log.e(TAG, "addProfile", ex)
-            app.track(ex)
+        val oldProfile = app.currentProfile
+        if (oldProfile != null) {
+            // Copy Feature Settings from old profile
+            profile.route = oldProfile.route
+            profile.ipv6 = oldProfile.ipv6
+            profile.proxyApps = oldProfile.proxyApps
+            profile.bypass = oldProfile.bypass
+            profile.individual = oldProfile.individual
+            profile.udpdns = oldProfile.udpdns
         }
+        val last = PrivateDatabase.profileDao.queryRaw(PrivateDatabase.profileDao.queryBuilder()
+                .selectRaw("MAX(userOrder)").prepareStatementString()).firstResult
+        if (last != null && last.size == 1 && last[0] != null) profile.userOrder = last[0].toLong() + 1
+        PrivateDatabase.profileDao.createOrUpdate(profile)
+        ProfilesFragment.instance?.profilesAdapter?.add(profile)
         return profile
     }
 
     /**
      * Note: It's caller's responsibility to update DirectBoot profile if necessary.
      */
-    fun updateProfile(profile: Profile): Boolean = try {
-        PrivateDatabase.profileDao.update(profile)
-        true
-    } catch (ex: Exception) {
-        Log.e(TAG, "updateProfile", ex)
-        app.track(ex)
-        false
-    }
+    @Throws(SQLException::class)
+    fun updateProfile(profile: Profile) = PrivateDatabase.profileDao.update(profile)
 
     fun getProfile(id: Int): Profile? = try {
         PrivateDatabase.profileDao.queryForId(id)
-    } catch (ex: Exception) {
+    } catch (ex: SQLException) {
         Log.e(TAG, "getProfile", ex)
         app.track(ex)
         null
     }
 
-    fun delProfile(id: Int): Boolean = try {
+    @Throws(SQLException::class)
+    fun delProfile(id: Int) {
         PrivateDatabase.profileDao.deleteById(id)
         ProfilesFragment.instance?.profilesAdapter?.removeId(id)
         if (id == DataStore.profileId && DataStore.directBootAware) DirectBoot.clean()
-        true
-    } catch (ex: Exception) {
-        Log.e(TAG, "delProfile", ex)
-        app.track(ex)
-        false
     }
 
     fun getFirstProfile(): Profile? = try {
-        val result = PrivateDatabase.profileDao.query(PrivateDatabase.profileDao.queryBuilder().limit(1L).prepare())
-        if (result.size == 1) result[0] else null
-    } catch (ex: Exception) {
-        Log.e(TAG, "getAllProfiles", ex)
+        PrivateDatabase.profileDao.query(PrivateDatabase.profileDao.queryBuilder().limit(1L).prepare()).singleOrNull()
+    } catch (ex: SQLException) {
+        Log.e(TAG, "getFirstProfile", ex)
         app.track(ex)
         null
     }
 
     fun getAllProfiles(): List<Profile>? = try {
         PrivateDatabase.profileDao.query(PrivateDatabase.profileDao.queryBuilder().orderBy("userOrder", true).prepare())
-    } catch (ex: Exception) {
+    } catch (ex: SQLException) {
         Log.e(TAG, "getAllProfiles", ex)
         app.track(ex)
         null
diff --git a/mobile/src/main/java/com/github/shadowsocks/preference/DataStore.kt b/mobile/src/main/java/com/github/shadowsocks/preference/DataStore.kt
index 87651719..7a9146b7 100644
--- a/mobile/src/main/java/com/github/shadowsocks/preference/DataStore.kt
+++ b/mobile/src/main/java/com/github/shadowsocks/preference/DataStore.kt
@@ -52,7 +52,7 @@ object DataStore {
     /**
      * Setter is defined in MainActivity.onPreferenceDataStoreChanged.
      */
-    val directBootAware: Boolean get() = BootReceiver.enabled && (publicStore.getBoolean(Key.directBootAware) ?: false)
+    val directBootAware: Boolean get() = BootReceiver.enabled && publicStore.getBoolean(Key.directBootAware) == true
     var serviceMode: String
         get() = publicStore.getString(Key.serviceMode) ?: Key.modeVpn
         set(value) = publicStore.putString(Key.serviceMode, value)
diff --git a/mobile/src/main/java/com/github/shadowsocks/preference/IconListPreference.kt b/mobile/src/main/java/com/github/shadowsocks/preference/IconListPreference.kt
index f1df51f2..7122a2e3 100644
--- a/mobile/src/main/java/com/github/shadowsocks/preference/IconListPreference.kt
+++ b/mobile/src/main/java/com/github/shadowsocks/preference/IconListPreference.kt
@@ -28,11 +28,7 @@ import android.util.AttributeSet
 class IconListPreference(context: Context, attrs: AttributeSet? = null) : ListPreference(context, attrs) {
     var entryIcons: Array<Drawable?>? = null
     val selectedEntry: Int get() = entryValues.indexOf(value)
-    val entryIcon: Drawable? get() = try {
-        entryIcons?.get(selectedEntry)
-    } catch (_: ArrayIndexOutOfBoundsException) {
-        null
-    }
+    val entryIcon: Drawable? get() = entryIcons?.getOrNull(selectedEntry)
 //    fun setEntryIcons(@ArrayRes entryIconsResId: Int) {
 //        val array = getContext().getResources().obtainTypedArray(entryIconsResId)
 //        entryIcons = Array(array.length(), { i -> array.getDrawable(i) })
@@ -49,7 +45,7 @@ class IconListPreference(context: Context, attrs: AttributeSet? = null) : ListPr
     }
 
     init {
-        super.setOnPreferenceChangeListener({ preference, newValue ->
+        super.setOnPreferenceChangeListener { preference, newValue ->
             val listener = listener
             if (listener == null || listener.onPreferenceChange(preference, newValue)) {
                 value = newValue.toString()
@@ -57,7 +53,7 @@ class IconListPreference(context: Context, attrs: AttributeSet? = null) : ListPr
                 if (entryIcons != null) icon = entryIcon
                 true
             } else false
-        })
+        }
 //        val a = context.obtainStyledAttributes(attrs, R.styleable.IconListPreference)
 //        val entryIconsResId: Int = a.getResourceId(R.styleable.IconListPreference_entryIcons, -1)
 //        if (entryIconsResId != -1) entryIcons = entryIconsResId
diff --git a/mobile/src/main/java/com/github/shadowsocks/tasker/ConfigActivity.kt b/mobile/src/main/java/com/github/shadowsocks/tasker/ConfigActivity.kt
index 602f75d7..fc9eeecf 100644
--- a/mobile/src/main/java/com/github/shadowsocks/tasker/ConfigActivity.kt
+++ b/mobile/src/main/java/com/github/shadowsocks/tasker/ConfigActivity.kt
@@ -85,12 +85,12 @@ class ConfigActivity : AppCompatActivity() {
 
     override fun onCreate(savedInstanceState: Bundle?) {
         super.onCreate(savedInstanceState)
-        try {
-            taskerOption = Settings.fromIntent(intent!!)
-        } catch (_: Exception) {
+        val intent = intent
+        if (intent == null) {
             finish()
             return
         }
+        taskerOption = Settings.fromIntent(intent)
         setContentView(R.layout.layout_tasker)
 
         val toolbar = findViewById<Toolbar>(R.id.toolbar)
diff --git a/mobile/src/main/java/com/github/shadowsocks/tasker/Settings.kt b/mobile/src/main/java/com/github/shadowsocks/tasker/Settings.kt
index b231c0cc..ed4e6f9c 100644
--- a/mobile/src/main/java/com/github/shadowsocks/tasker/Settings.kt
+++ b/mobile/src/main/java/com/github/shadowsocks/tasker/Settings.kt
@@ -44,8 +44,8 @@ class Settings(bundle: Bundle?) {
         if (profileId >= 0) bundle.putInt(KEY_PROFILE_ID, profileId)
         val profile = ProfileManager.getProfile(profileId)
         return Intent().putExtra(ApiIntent.EXTRA_BUNDLE, bundle).putExtra(ApiIntent.EXTRA_STRING_BLURB,
-                if (profile != null)
-                    context.getString(if (switchOn) R.string.start_service else R.string.stop_service, profile.formattedName)
+                if (profile != null) context.getString(if (switchOn) R.string.start_service else R.string.stop_service,
+                        profile.formattedName)
                 else context.getString(if (switchOn) R.string.start_service_default else R.string.stop))
     }
 }
diff --git a/mobile/src/main/java/com/github/shadowsocks/utils/Commandline.kt b/mobile/src/main/java/com/github/shadowsocks/utils/Commandline.kt
index 35096d5e..28569627 100644
--- a/mobile/src/main/java/com/github/shadowsocks/utils/Commandline.kt
+++ b/mobile/src/main/java/com/github/shadowsocks/utils/Commandline.kt
@@ -20,9 +20,7 @@
 
 package com.github.shadowsocks.utils
 
-import java.util.ArrayList
-import java.util.Arrays
-import java.util.StringTokenizer
+import java.util.*
 
 /**
  * Commandline objects help handling command lines specifying processes to
@@ -86,9 +84,7 @@ object Commandline {
      * @return empty string for null or no command, else every argument split
      * by spaces and quoted by quoting rules.
      */
-    fun toString(args: Array<String>): String {
-        return toString(Arrays.asList(*args))   // thanks to Java, arrays aren't iterable
-    }
+    fun toString(args: Array<String>) = toString(args.asIterable()) // thanks to Java, arrays aren't iterable
 
     /**
      * Crack a command line.
diff --git a/mobile/src/main/java/com/github/shadowsocks/utils/DirectBoot.kt b/mobile/src/main/java/com/github/shadowsocks/utils/DirectBoot.kt
index 9bf345fd..228e0c97 100644
--- a/mobile/src/main/java/com/github/shadowsocks/utils/DirectBoot.kt
+++ b/mobile/src/main/java/com/github/shadowsocks/utils/DirectBoot.kt
@@ -7,7 +7,7 @@ import com.github.shadowsocks.database.Profile
 import com.github.shadowsocks.database.ProfileManager
 import com.github.shadowsocks.preference.DataStore
 import java.io.File
-import java.io.FileNotFoundException
+import java.io.IOException
 import java.io.ObjectInputStream
 import java.io.ObjectOutputStream
 
@@ -17,7 +17,7 @@ object DirectBoot {
 
     fun getDeviceProfile(): Profile? = try {
         ObjectInputStream(file.inputStream()).use { it.readObject() as Profile }
-    } catch (_: FileNotFoundException) { null }
+    } catch (_: IOException) { null }
 
     fun clean() {
         file.delete()
diff --git a/mobile/src/main/java/com/github/shadowsocks/utils/Utils.kt b/mobile/src/main/java/com/github/shadowsocks/utils/Utils.kt
index e328fcff..f8d3e66f 100644
--- a/mobile/src/main/java/com/github/shadowsocks/utils/Utils.kt
+++ b/mobile/src/main/java/com/github/shadowsocks/utils/Utils.kt
@@ -28,8 +28,8 @@ fun String.parseNumericAddress(): InetAddress? {
 }
 
 fun parsePort(str: String?, default: Int, min: Int = 1025): Int {
-    val x = str?.toIntOrNull() ?: default
-    return if (x < min || x > 65535) default else x
+    val value = str?.toIntOrNull() ?: default
+    return if (value < min || value > 65535) default else value
 }
 
 fun broadcastReceiver(callback: (Context, Intent) -> Unit): BroadcastReceiver = object : BroadcastReceiver() {
@@ -72,6 +72,6 @@ private class SortedListIterable<out T>(private val list: SortedList<T>) : Itera
 private class SortedListIterator<out T>(private val list: SortedList<T>) : Iterator<T> {
     private var count = 0
     override fun hasNext() = count < list.size()
-    override fun next(): T = list[count++]
+    override fun next(): T = if (hasNext()) list[count++] else throw NoSuchElementException()
 }
 fun <T> SortedList<T>.asIterable(): Iterable<T> = SortedListIterable(this)
diff --git a/mobile/src/main/java/com/github/shadowsocks/widget/ServiceButton.kt b/mobile/src/main/java/com/github/shadowsocks/widget/ServiceButton.kt
index 670f68de..963cfaa0 100644
--- a/mobile/src/main/java/com/github/shadowsocks/widget/ServiceButton.kt
+++ b/mobile/src/main/java/com/github/shadowsocks/widget/ServiceButton.kt
@@ -29,7 +29,6 @@ import android.support.graphics.drawable.AnimatedVectorDrawableCompat
 import android.support.v7.widget.TooltipCompat
 import android.util.AttributeSet
 import android.view.View
-import com.github.shadowsocks.App.Companion.app
 import com.github.shadowsocks.R
 import com.github.shadowsocks.bg.BaseService
 import java.util.*
diff --git a/plugin/src/main/java/com/github/shadowsocks/plugin/NativePluginProvider.kt b/plugin/src/main/java/com/github/shadowsocks/plugin/NativePluginProvider.kt
index 104484d7..7aaef405 100644
--- a/plugin/src/main/java/com/github/shadowsocks/plugin/NativePluginProvider.kt
+++ b/plugin/src/main/java/com/github/shadowsocks/plugin/NativePluginProvider.kt
@@ -70,8 +70,8 @@ abstract class NativePluginProvider : ContentProvider() {
     /**
      * Returns executable entry absolute path. This is used if plugin is sharing UID with the host.
      *
-     * Default behavior is throwing UnsupportedOperationException. If you don't wish to use this feature, use the default
-     * behavior.
+     * Default behavior is throwing UnsupportedOperationException. If you don't wish to use this feature, use the
+     * default behavior.
      *
      * @return Absolute path for executable entry.
      */
diff --git a/plugin/src/main/java/com/github/shadowsocks/plugin/OptionsCapableActivity.kt b/plugin/src/main/java/com/github/shadowsocks/plugin/OptionsCapableActivity.kt
index 48809668..5497e725 100644
--- a/plugin/src/main/java/com/github/shadowsocks/plugin/OptionsCapableActivity.kt
+++ b/plugin/src/main/java/com/github/shadowsocks/plugin/OptionsCapableActivity.kt
@@ -29,13 +29,11 @@ import android.widget.Toast
  * Activity that's capable of getting EXTRA_OPTIONS input.
  */
 abstract class OptionsCapableActivity : AppCompatActivity() {
-    protected fun pluginOptions(intent: Intent = this.intent): PluginOptions {
-        return try {
-            PluginOptions(intent.getStringExtra(PluginContract.EXTRA_OPTIONS))
-        } catch (exc: IllegalArgumentException) {
-            Toast.makeText(this, exc.message, Toast.LENGTH_SHORT).show()
-            PluginOptions()
-        }
+    protected fun pluginOptions(intent: Intent = this.intent) = try {
+        PluginOptions(intent.getStringExtra(PluginContract.EXTRA_OPTIONS))
+    } catch (exc: IllegalArgumentException) {
+        Toast.makeText(this, exc.message, Toast.LENGTH_SHORT).show()
+        PluginOptions()
     }
 
     /**