examples: Implement console progress bar for GetObject (#554)

Progress bar is of the following form

```
Uploading...    2% [=>                         ]   ...
```

examples/GetObjectProgressBar.java

@@ -0,0 +1,78 @@
+/*
+ * Minio Java SDK for Amazon S3 Compatible Cloud Storage, (C) 2017 Minio, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.OutputStream;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.nio.file.Paths;
+import java.nio.file.StandardOpenOption;
+import java.security.InvalidKeyException;
+import java.security.NoSuchAlgorithmException;
+
+import org.xmlpull.v1.XmlPullParserException;
+
+import com.google.common.io.ByteStreams;
+
+import io.minio.MinioClient;
+import io.minio.ObjectStat;
+import io.minio.errors.MinioException;
+import me.tongfei.progressbar.ProgressBarStyle;
+
+public class GetObjectProgressBar {
+  /**
+   * MinioClient.getObjectProgressBar() example.
+   */
+  public static void main(String[] args)
+      throws IOException, NoSuchAlgorithmException, InvalidKeyException, XmlPullParserException {
+    try {
+      /* play.minio.io for test and development. */
+      MinioClient minioClient = new MinioClient("https://play.minio.io:9000",
+          "Q3AM3UQ867SPQQA43P2F", "zuf+tfteSlswRu7BJ86wekitnifILbZam1KYY3TG");
+
+      /* Amazon S3: */
+      // MinioClient minioClient = new MinioClient("https://s3.amazonaws.com", "YOUR-ACCESSKEYID",
+      // "YOUR-SECRETACCESSKEY");
+
+      // Check whether the object exists using statObject(). If the object is not found,
+      // statObject() throws an exception. It means that the object exists when statObject()
+      // execution is successful.
+
+      // Get object stat information.
+      ObjectStat objectStat = minioClient.statObject("testbucket", "resumes/4.original.pdf");
+
+      // Get input stream to have content of 'my-objectname' from 'my-bucketname'
+      InputStream is = new ProgressStream("Downloading .. ", ProgressBarStyle.ASCII,
+          objectStat.length(), minioClient.getObject("my-bucketname", "my-objectname"));
+
+      Path path = Paths.get("my-filename");
+      OutputStream os = Files.newOutputStream(path, StandardOpenOption.CREATE);
+
+      long bytesWritten = ByteStreams.copy(is, os);
+      is.close();
+      os.close();
+
+      if (bytesWritten != objectStat.length()) {
+        throw new IOException(path + ": unexpected data written.  expected = " + objectStat.length()
+            + ", written = " + bytesWritten);
+      }
+
+    } catch (MinioException e) {
+      System.out.println("Error occurred: " + e);
+    }
+  }
+}

examples/ProgressStream.java

@@ -25,23 +25,40 @@ public class ProgressStream extends InputStream {
   private ProgressBar pb;
 
   /**
-   * ProgressStream implements an extends InputStream while
-   * also writing out the read progress on console. ProgressStream
-   * can be used as a direct replacement for any InputStream compatible
+   * ProgressStream implements an extends InputStream while also writing out the read progress on
+   * console. ProgressStream can be used as a direct replacement for any InputStream compatible
    * input.
+   * 
+   * @param msg Custom message string.
+   * @param style Custom progress bar style.
    * @param stream InputStream to be wrapped.
    * @throws IOException For any exception generated by the InputStream.
    */
   public ProgressStream(String msg, ProgressBarStyle style, InputStream stream) throws IOException {
+    this(msg, style, (long)stream.available(), stream);
+  }
+
+  /**
+   * ProgressStream implements an extends InputStream while also writing out the read progress on
+   * console. ProgressStream can be used as a direct replacement for any InputStream compatible
+   * input.
+   * 
+   * @param msg Custom message string.
+   * @param style Custom progress bar style.
+   * @param size Size of the progress bar.
+   * @param stream InputStream to be wrapped.
+   * @throws IOException For any exception generated by the InputStream.
+   */
+  public ProgressStream(String msg, ProgressBarStyle style, long size, InputStream stream)
+      throws IOException {
     super();
 
     // Allocate the reader.
     this.in = stream;
 
     // Initialize progress bar.
-    this.pb = new ProgressBar(msg, stream.available(), style);
+    this.pb = new ProgressBar(msg, size, style);
     this.pb.start();
-
   }
 
   @Override
@@ -64,14 +81,16 @@ public int read() throws IOException {
 
   @Override
   public int read(byte[] toStore) throws IOException {
-    this.pb.stepBy(toStore.length); // Update progress bar.
-    return this.in.read(toStore);
+    int readBytes = this.in.read(toStore);
+    this.pb.stepBy(readBytes); // Update progress bar.
+    return readBytes;
   }
 
   @Override
   public int read(byte[] toStore, int off, int len) throws IOException {
-    this.pb.stepBy(toStore.length);
-    return this.in.read(toStore, off, len);
+    int readBytes = this.in.read(toStore, off, len);
+    this.pb.stepBy(readBytes);
+    return readBytes;
   }
 
   @Override