HADOOP-14119. Remove unused imports from GzipCodec.java. Contributed by Yiqun Lin.

(cherry picked from commit 9db2e0c8d4b29971da60e2628ff55b5dabed2f7b)

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/io/compress/GzipCodec.java

@@ -18,18 +18,21 @@
 
 package org.apache.hadoop.io.compress;
 
-import java.io.*;
+import static org.apache.hadoop.fs.CommonConfigurationKeysPublic.IO_FILE_BUFFER_SIZE_DEFAULT;
+import static org.apache.hadoop.fs.CommonConfigurationKeysPublic.IO_FILE_BUFFER_SIZE_KEY;
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.OutputStream;
 import java.util.zip.GZIPOutputStream;
+
 import org.apache.hadoop.classification.InterfaceAudience;
 import org.apache.hadoop.classification.InterfaceStability;
 import org.apache.hadoop.conf.Configuration;
-import org.apache.hadoop.io.compress.DefaultCodec;
-import org.apache.hadoop.io.compress.zlib.*;
-import org.apache.hadoop.io.compress.zlib.ZlibDecompressor.ZlibDirectDecompressor;
-
-import static org.apache.hadoop.fs.CommonConfigurationKeysPublic.IO_FILE_BUFFER_SIZE_DEFAULT;
-import static org.apache.hadoop.fs.CommonConfigurationKeysPublic.IO_FILE_BUFFER_SIZE_KEY;
-import static org.apache.hadoop.util.PlatformName.IBM_JAVA;
+import org.apache.hadoop.io.compress.zlib.BuiltInGzipDecompressor;
+import org.apache.hadoop.io.compress.zlib.ZlibCompressor;
+import org.apache.hadoop.io.compress.zlib.ZlibDecompressor;
+import org.apache.hadoop.io.compress.zlib.ZlibFactory;
 
 /**
  * This class creates gzip compressors/decompressors.