Clean up AdBlock class

* use interface instead of concrete class
* inline initialization of static variable
* remove redundant field and variable initialization
* replace single-character string with char

src/acr/browser/lightning/AdBlock.java

@@ -10,21 +10,19 @@ import java.io.InputStream;
 import java.io.InputStreamReader;
 import java.net.URI;
 import java.net.URISyntaxException;
+import java.util.SortedMap;
 import java.util.TreeMap;
 
 public class AdBlock {
 
-	private static TreeMap<String, Integer> mAdBlockMap = null;
+	private static SortedMap<String, Integer> mAdBlockMap =
+			new TreeMap<String, Integer>(String.CASE_INSENSITIVE_ORDER);
 
 	private SharedPreferences mPreferences;
 
-	private boolean mBlockAds = false;
+	private boolean mBlockAds;
 
 	public AdBlock(Context context) {
-		if (mAdBlockMap == null) {
-			mAdBlockMap = new TreeMap<String, Integer>(
-					String.CASE_INSENSITIVE_ORDER);
-		}
 		if (mAdBlockMap.isEmpty()) {
 			fillSearchTree(context);
 		}
@@ -68,7 +66,7 @@ public class AdBlock {
 		if (!mBlockAds) {
 			return false;
 		}
-		String domain = "";
+		String domain;
 		try {
 			domain = getDomainName(url);
 		} catch (URISyntaxException e) {
@@ -79,7 +77,7 @@ public class AdBlock {
 	}
 
 	private static String getDomainName(String url) throws URISyntaxException {
-		int index = url.indexOf("/", 8);
+		int index = url.indexOf('/', 8);
 		if (index != -1) {
 			url = url.substring(0, index);
 		}