correct some code and add more doc

Signed-off-by: Kevin Liu <airk908@gmail.com>

sobitmap/src/main/java/com/github/airk/tool/sobitmap/Callback.java

@@ -25,7 +25,7 @@
  * Hunter's callback
  */
 public interface Callback {
-    public void onHunted(Bitmap bitmap, BitmapFactory.Options options);
+    void onHunted(Bitmap bitmap, BitmapFactory.Options options);
 
-    public void onException(HuntException e);
+    void onException(HuntException e);
 }

sobitmap/src/main/java/com/github/airk/tool/sobitmap/Options.java

@@ -51,7 +51,7 @@ public final class Options {
      */
     final Bitmap.CompressFormat format;
 
-    public static enum QualityLevel {
+    public enum QualityLevel {
         HIGH {
             @Override
             int getStep() {
@@ -97,6 +97,15 @@ float getMemoryFactor() {
         abstract float getMemoryFactor();
     }
 
+    /**
+     * Use detail parameters construct display option
+     *
+     * @param maxInput    Max input in memory
+     * @param maxOutput   Max output in memory
+     * @param maxSize     The max display size in pixel
+     * @param qualityStep quality down step
+     * @param format      JPG\PNG\WEBP
+     */
     public Options(long maxInput, long maxOutput, int maxSize, int qualityStep, Bitmap.CompressFormat format) {
         this.maxInput = maxInput;
         this.maxOutput = maxOutput;
@@ -108,6 +117,13 @@ public Options(long maxInput, long maxOutput, int maxSize, int qualityStep, Bitm
         level = null;
     }
 
+    /**
+     * Use level to construct display option, don't care about the detail inside.
+     *
+     * @param maxSize The max display size in pixel
+     * @param format  JPG\PNG\WEBP
+     * @param level   {@link com.github.airk.tool.sobitmap.Options.QualityLevel}
+     */
     public Options(int maxSize, Bitmap.CompressFormat format, QualityLevel level) {
         this.maxSize = maxSize;
         this.format = format;
@@ -128,9 +144,8 @@ public boolean equals(Object o) {
         if (maxSize != options.maxSize) return false;
         if (qualityStep != options.qualityStep) return false;
         if (format != options.format) return false;
-        if (level != options.level) return false;
+        return level == options.level;
 
-        return true;
     }
 
     @Override

sobitmap/src/main/java/com/github/airk/tool/sobitmap/Request.java

@@ -51,7 +51,7 @@ final class Request implements Callback, Runnable {
     Request(Context context, String tag, Uri source, Options options, Callback callback, Hunter target, Handler handler, File dir) {
         this.context = context;
         if (tag == null) {
-            this.tag = "sobitmap_request_" + Integer.toHexString(this.hashCode());
+            this.tag = "sobitmap:request:" + Integer.toHexString(this.hashCode());
         } else {
             this.tag = tag;
         }

sobitmap/src/main/java/com/github/airk/tool/sobitmap/SoBitmap.java

@@ -49,7 +49,7 @@ public final class SoBitmap {
      */
     static boolean LOG = Log.isLoggable(TAG, Log.VERBOSE);
 
-    private volatile static SoBitmap INSTANCE;
+    private volatile static SoBitmap sInstance;
     private Context context;
     private Options defaultOps;
     private File cacheDir;
@@ -94,31 +94,31 @@ public boolean handleMessage(Message msg) {
      * @return SoBitmap instance
      */
     public static SoBitmap getInstance(Context context) {
-        if (INSTANCE == null) {
+        if (sInstance == null) {
             synchronized (SoBitmap.class) {
-                if (INSTANCE == null) {
-                    INSTANCE = new SoBitmap(context);
+                if (sInstance == null) {
+                    sInstance = new SoBitmap(context);
                 }
             }
         }
-        return INSTANCE;
+        return sInstance;
     }
 
     /**
      * User can set SoBitmap's singleton instance to follow what he want by using this method. The Builder{@link com.github.airk.tool.sobitmap.SoBitmap.Builder}
      * can give users more opportunity to custom SoBitmap but not invoke the SoBitmap's constructor immediately, so we can keep SoBitmap's singleton mode safe.
-     * ps: the method must be invoked before {@link #getInstance(android.content.Context)}, otherwise there will be a IllegalArgumentException.
+     * ps: the method must be invoked before {@link #getInstance(android.content.Context)}, otherwise there will be a IllegalStateException.
      *
      * @param context Context
      * @param builder {@link com.github.airk.tool.sobitmap.SoBitmap.Builder}
      * @return SoBitmap instance
      */
     public static SoBitmap setInstanceByBuilder(Context context, Builder builder) {
-        if (INSTANCE != null) {
-            throw new IllegalArgumentException("Singleton instance has been created, please call this method before getInstance(Context)");
+        if (sInstance != null) {
+            throw new IllegalStateException("Singleton instance has been created, please call this method before getInstance(Context)");
         }
-        INSTANCE = new SoBitmap(context, builder.useExternalCache);
-        return INSTANCE;
+        sInstance = new SoBitmap(context, builder.useExternalCache);
+        return sInstance;
     }
 
     /**
@@ -127,6 +127,11 @@ public static SoBitmap setInstanceByBuilder(Context context, Builder builder) {
     public static class Builder {
         boolean useExternalCache = true;
 
+        /**
+         * Shall SoBitmap use external storage for cache, default is true.
+         *
+         * @param useExternalCache true for use
+         */
         public void setUseExternalCache(boolean useExternalCache) {
             this.useExternalCache = useExternalCache;
         }
@@ -148,7 +153,7 @@ private SoBitmap(Context context, boolean useExternalCache) {
         for (Class<? extends Hunter> cls : HUNTERS) {
             try {
                 hunterSet.add(cls.newInstance());
-            } catch (InstantiationException | IllegalAccessException ignore) {
+            } catch (Exception ignore) {
             }
         }
         if (useExternalCache) {
@@ -170,8 +175,8 @@ private SoBitmap(Context context, boolean useExternalCache) {
      * @return SoBitmap single instance
      */
     public SoBitmap setDefaultOption(Options option) {
-        INSTANCE.defaultOps = option;
-        return INSTANCE;
+        sInstance.defaultOps = option;
+        return sInstance;
     }
 
     /**
@@ -182,7 +187,7 @@ public SoBitmap setDefaultOption(Options option) {
      * @return true if hunt in process successful, false otherwise
      */
     public boolean hunt(Uri uri, Callback callback) {
-        return hunt(null, uri, INSTANCE.defaultOps, callback);
+        return hunt(null, uri, sInstance.defaultOps, callback);
     }
 
     /**
@@ -194,7 +199,7 @@ public boolean hunt(Uri uri, Callback callback) {
      * @return true if hunt in process successful, false otherwise
      */
     public boolean hunt(String tag, Uri uri, Callback callback) {
-        return hunt(tag, uri, INSTANCE.defaultOps, callback);
+        return hunt(tag, uri, sInstance.defaultOps, callback);
     }
 
     /**
@@ -326,7 +331,7 @@ public void shutdown() {
             Log.d(TAG, "SoBitmap Shutdown!");
         }
         executor.shutdownNow();
-        INSTANCE = null;
+        sInstance = null;
     }
 
 }