diff --git a/app/src/LightningPlus/java/acr/browser/lightning/utils/ProxyUtils.java b/app/src/LightningPlus/java/acr/browser/lightning/utils/ProxyUtils.java
index 269c185..d49f9f2 100644
--- a/app/src/LightningPlus/java/acr/browser/lightning/utils/ProxyUtils.java
+++ b/app/src/LightningPlus/java/acr/browser/lightning/utils/ProxyUtils.java
@@ -3,7 +3,6 @@ package acr.browser.lightning.utils;
 import android.app.Activity;
 import android.content.Context;
 import android.content.DialogInterface;
-import android.support.annotation.NonNull;
 import android.support.v7.app.AlertDialog;
 import android.util.Log;
 
diff --git a/app/src/main/java/acr/browser/lightning/activity/BrowserActivity.java b/app/src/main/java/acr/browser/lightning/activity/BrowserActivity.java
index acf0003..0e361aa 100644
--- a/app/src/main/java/acr/browser/lightning/activity/BrowserActivity.java
+++ b/app/src/main/java/acr/browser/lightning/activity/BrowserActivity.java
@@ -1220,13 +1220,13 @@ public abstract class BrowserActivity extends ThemableBrowserActivity implements
 
     void saveOpenTabs() {
         if (mPreferences.getRestoreLostTabsEnabled()) {
-            String s = "";
+            StringBuilder s = new StringBuilder(mWebViewList.size() * 50);
             for (int n = 0, size = mWebViewList.size(); n < size; n++) {
                 if (!mWebViewList.get(n).getUrl().isEmpty()) {
-                    s = s + mWebViewList.get(n).getUrl() + "|$|SEPARATOR|$|";
+                    s.append(mWebViewList.get(n).getUrl()).append("|$|SEPARATOR|$|");
                 }
             }
-            mPreferences.setMemoryUrl(s);
+            mPreferences.setMemoryUrl(s.toString());
         }
     }
 
diff --git a/app/src/main/java/acr/browser/lightning/object/SearchAdapter.java b/app/src/main/java/acr/browser/lightning/object/SearchAdapter.java
index c79bb54..2ef2151 100644
--- a/app/src/main/java/acr/browser/lightning/object/SearchAdapter.java
+++ b/app/src/main/java/acr/browser/lightning/object/SearchAdapter.java
@@ -48,11 +48,11 @@ import acr.browser.lightning.utils.Utils;
 
 public class SearchAdapter extends BaseAdapter implements Filterable {
 
-    private final List<HistoryItem> mHistory = new ArrayList<>();
-    private final List<HistoryItem> mBookmarks = new ArrayList<>();
-    private final List<HistoryItem> mSuggestions = new ArrayList<>();
-    private final List<HistoryItem> mFilteredList = new ArrayList<>();
-    private final List<HistoryItem> mAllBookmarks = new ArrayList<>();
+    private final List<HistoryItem> mHistory = new ArrayList<>(5);
+    private final List<HistoryItem> mBookmarks = new ArrayList<>(5);
+    private final List<HistoryItem> mSuggestions = new ArrayList<>(5);
+    private final List<HistoryItem> mFilteredList = new ArrayList<>(5);
+    private final List<HistoryItem> mAllBookmarks = new ArrayList<>(5);
     private final Object mLock = new Object();
     private HistoryDatabase mDatabaseHandler;
     private final Context mContext;
diff --git a/app/src/main/java/acr/browser/lightning/reading/Converter.java b/app/src/main/java/acr/browser/lightning/reading/Converter.java
index 33a7088..0449667 100644
--- a/app/src/main/java/acr/browser/lightning/reading/Converter.java
+++ b/app/src/main/java/acr/browser/lightning/reading/Converter.java
@@ -204,24 +204,24 @@ public class Converter {
             int lastEncIndex;
             if (startChar == '\'')
                 // if we have charset='something'
-                lastEncIndex = str.indexOf("'", ++encIndex + clength);
+                lastEncIndex = str.indexOf('\'', ++encIndex + clength);
             else if (startChar == '\"')
                 // if we have charset="something"
-                lastEncIndex = str.indexOf("\"", ++encIndex + clength);
+                lastEncIndex = str.indexOf('\"', ++encIndex + clength);
             else {
                 // if we have "text/html; charset=utf-8"
-                int first = str.indexOf("\"", encIndex + clength);
+                int first = str.indexOf('\"', encIndex + clength);
                 if (first < 0)
                     first = Integer.MAX_VALUE;
 
                 // or "text/html; charset=utf-8 "
-                int sec = str.indexOf(" ", encIndex + clength);
+                int sec = str.indexOf(' ', encIndex + clength);
                 if (sec < 0)
                     sec = Integer.MAX_VALUE;
                 lastEncIndex = Math.min(first, sec);
 
                 // or "text/html; charset=utf-8 '
-                int third = str.indexOf("'", encIndex + clength);
+                int third = str.indexOf('\'', encIndex + clength);
                 if (third > 0)
                     lastEncIndex = Math.min(lastEncIndex, third);
             }
diff --git a/app/src/main/java/acr/browser/lightning/reading/HtmlFetcher.java b/app/src/main/java/acr/browser/lightning/reading/HtmlFetcher.java
index 9ccfa04..7ff9e0d 100644
--- a/app/src/main/java/acr/browser/lightning/reading/HtmlFetcher.java
+++ b/app/src/main/java/acr/browser/lightning/reading/HtmlFetcher.java
@@ -28,6 +28,7 @@ import java.net.URL;
 import java.util.LinkedHashSet;
 import java.util.Set;
 import java.util.concurrent.atomic.AtomicInteger;
+import java.util.regex.Pattern;
 import java.util.zip.GZIPInputStream;
 import java.util.zip.Inflater;
 import java.util.zip.InflaterInputStream;
@@ -39,6 +40,8 @@ import java.util.zip.InflaterInputStream;
  */
 public class HtmlFetcher {
 
+    private static final Pattern SPACE = Pattern.compile(" ");
+
     static {
         SHelper.enableCookieMgmt();
         SHelper.enableUserAgentOverwrite();
@@ -50,8 +53,8 @@ public class HtmlFetcher {
         String line;
         Set<String> existing = new LinkedHashSet<>();
         while ((line = reader.readLine()) != null) {
-            int index1 = line.indexOf("\"");
-            int index2 = line.indexOf("\"", index1 + 1);
+            int index1 = line.indexOf('\"');
+            int index2 = line.indexOf('\"', index1 + 1);
             String url = line.substring(index1 + 1, index2);
             String domainStr = SHelper.extractDomain(url, true);
             String counterStr = "";
@@ -381,7 +384,7 @@ public class HtmlFetcher {
             newUrl = hConn.getHeaderField("Location");
             // Note that the max recursion level is 5.
             if (responseCode / 100 == 3 && newUrl != null && num_redirects < 5) {
-                newUrl = newUrl.replaceAll(" ", "+");
+                newUrl = SPACE.matcher(newUrl).replaceAll("+");
                 // some services use (none-standard) utf8 in their location header
                 if (urlAsString.startsWith("http://bit.ly")
                         || urlAsString.startsWith("http://is.gd"))
diff --git a/app/src/main/java/acr/browser/lightning/reading/JResult.java b/app/src/main/java/acr/browser/lightning/reading/JResult.java
index dc97de2..fb9d2dc 100644
--- a/app/src/main/java/acr/browser/lightning/reading/JResult.java
+++ b/app/src/main/java/acr/browser/lightning/reading/JResult.java
@@ -230,7 +230,7 @@ public class JResult implements Serializable {
     }
 
     public void addLink(String url, String text, Integer pos) {
-        Map link = new HashMap();
+        Map<String, String> link = new HashMap<>();
         link.put("url", url);
         link.put("text", text);
         link.put("offset", String.valueOf(pos));
diff --git a/app/src/main/java/acr/browser/lightning/reading/SHelper.java b/app/src/main/java/acr/browser/lightning/reading/SHelper.java
index f05d879..7b53851 100644
--- a/app/src/main/java/acr/browser/lightning/reading/SHelper.java
+++ b/app/src/main/java/acr/browser/lightning/reading/SHelper.java
@@ -193,7 +193,7 @@ public class SHelper {
                 url = url.substring("m.".length());
         }
 
-        int slashIndex = url.indexOf("/");
+        int slashIndex = url.indexOf('/');
         if (slashIndex > 0)
             url = url.substring(0, slashIndex);