HDFS-16092. Avoid creating LayoutFlags redundant objects (#3150)

(cherry picked from commit 93a1685073d76bef5c6ad3819e7710317733bd7a)
(cherry picked from commit 8538881710df3dd33ab23670d50d1b0119930169)

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/protocol/LayoutFlags.java

@@ -36,14 +36,15 @@ import com.google.common.collect.Sets;
  */
 @InterfaceAudience.Private
 public class LayoutFlags {
+
   /**
-   * Load a LayoutFlags object from a stream.
+   * Read next int from given input stream. If the value is not 0 (unsupported
+   * feature flags), throw appropriate IOException.
    *
    * @param in            The stream to read from.
-   * @throws IOException
+   * @throws IOException  If next byte read from given stream is not 0.
    */
-  public static LayoutFlags read(DataInputStream in)
-      throws IOException {
+  public static void read(DataInputStream in) throws IOException {
     int length = in.readInt();
     if (length < 0) {
       throw new IOException("The length of the feature flag section " +
@@ -52,7 +53,6 @@ public class LayoutFlags {
       throw new IOException("Found feature flags which we can't handle. " +
           "Please upgrade your software.");
     }
-    return new LayoutFlags();
   }
 
   private LayoutFlags() {