http://netty.io/netty-all/: Netty is an asynchronous event-driven network application framework for rapid development of maintainable high performance protocol servers and clients. (The Netty Project) 
public final class io.netty.handler.codec.mqtt.MqttVersion extends java.lang.Enum<io.netty.handler.codec.mqtt.MqttVersion>
  minor version: 0
  major version: 59
  flags: flags: (0x4031) ACC_PUBLIC, ACC_FINAL, ACC_SUPER, ACC_ANNOTATION
  this_class: io.netty.handler.codec.mqtt.MqttVersion
  super_class: java.lang.Enum
{
  public static final io.netty.handler.codec.mqtt.MqttVersion MQTT_3_1;
    descriptor: Lio/netty/handler/codec/mqtt/MqttVersion;
    flags: (0x4019) ACC_PUBLIC, ACC_STATIC, ACC_FINAL, ACC_ANNOTATION

  public static final io.netty.handler.codec.mqtt.MqttVersion MQTT_3_1_1;
    descriptor: Lio/netty/handler/codec/mqtt/MqttVersion;
    flags: (0x4019) ACC_PUBLIC, ACC_STATIC, ACC_FINAL, ACC_ANNOTATION

  private final java.lang.String name;
    descriptor: Ljava/lang/String;
    flags: (0x0012) ACC_PRIVATE, ACC_FINAL

  private final byte level;
    descriptor: B
    flags: (0x0012) ACC_PRIVATE, ACC_FINAL

  private static final io.netty.handler.codec.mqtt.MqttVersion[] ENUM$VALUES;
    descriptor: [Lio/netty/handler/codec/mqtt/MqttVersion;
    flags: (0x101a) ACC_PRIVATE, ACC_STATIC, ACC_FINAL, ACC_SYNTHETIC

  static void <clinit>();
    descriptor: ()V
    flags: (0x0008) ACC_STATIC
    Code:
      stack=6, locals=0, args_size=0
         0: .line 26
            new io.netty.handler.codec.mqtt.MqttVersion
            dup
            ldc "MQTT_3_1"
            iconst_0
            ldc "MQIsdp"
            iconst_3
            invokespecial io.netty.handler.codec.mqtt.MqttVersion.<init>:(Ljava/lang/String;ILjava/lang/String;B)V
            putstatic io.netty.handler.codec.mqtt.MqttVersion.MQTT_3_1:Lio/netty/handler/codec/mqtt/MqttVersion;
         1: .line 27
            new io.netty.handler.codec.mqtt.MqttVersion
            dup
            ldc "MQTT_3_1_1"
            iconst_1
            ldc "MQTT"
            iconst_4
            invokespecial io.netty.handler.codec.mqtt.MqttVersion.<init>:(Ljava/lang/String;ILjava/lang/String;B)V
            putstatic io.netty.handler.codec.mqtt.MqttVersion.MQTT_3_1_1:Lio/netty/handler/codec/mqtt/MqttVersion;
         2: .line 25
            iconst_2
            anewarray io.netty.handler.codec.mqtt.MqttVersion
            dup
            iconst_0
            getstatic io.netty.handler.codec.mqtt.MqttVersion.MQTT_3_1:Lio/netty/handler/codec/mqtt/MqttVersion;
            aastore
            dup
            iconst_1
            getstatic io.netty.handler.codec.mqtt.MqttVersion.MQTT_3_1_1:Lio/netty/handler/codec/mqtt/MqttVersion;
            aastore
            putstatic io.netty.handler.codec.mqtt.MqttVersion.ENUM$VALUES:[Lio/netty/handler/codec/mqtt/MqttVersion;
            return
      LocalVariableTable:
        Start  End  Slot  Name  Signature

  private void <init>(java.lang.String, int, java.lang.String, byte);
    descriptor: (Ljava/lang/String;ILjava/lang/String;B)V
    flags: (0x0002) ACC_PRIVATE
    Code:
      stack=3, locals=5, args_size=5
        start local 0 // io.netty.handler.codec.mqtt.MqttVersion this
        start local 3 // java.lang.String protocolName
        start local 4 // byte protocolLevel
         0: .line 32
            aload 0 /* this */
            aload 1
            iload 2
            invokespecial java.lang.Enum.<init>:(Ljava/lang/String;I)V
         1: .line 33
            aload 0 /* this */
            aload 3 /* protocolName */
            ldc "protocolName"
            invokestatic io.netty.util.internal.ObjectUtil.checkNotNull:(Ljava/lang/Object;Ljava/lang/String;)Ljava/lang/Object;
            checkcast java.lang.String
            putfield io.netty.handler.codec.mqtt.MqttVersion.name:Ljava/lang/String;
         2: .line 34
            aload 0 /* this */
            iload 4 /* protocolLevel */
            putfield io.netty.handler.codec.mqtt.MqttVersion.level:B
         3: .line 35
            return
        end local 4 // byte protocolLevel
        end local 3 // java.lang.String protocolName
        end local 0 // io.netty.handler.codec.mqtt.MqttVersion this
      LocalVariableTable:
        Start  End  Slot           Name  Signature
            0    4     0           this  Lio/netty/handler/codec/mqtt/MqttVersion;
            0    4     3   protocolName  Ljava/lang/String;
            0    4     4  protocolLevel  B
    MethodParameters:
               Name  Flags
      $enum$name     
      $enum$ordinal  
      protocolName   
      protocolLevel  

  public java.lang.String protocolName();
    descriptor: ()Ljava/lang/String;
    flags: (0x0001) ACC_PUBLIC
    Code:
      stack=1, locals=1, args_size=1
        start local 0 // io.netty.handler.codec.mqtt.MqttVersion this
         0: .line 38
            aload 0 /* this */
            getfield io.netty.handler.codec.mqtt.MqttVersion.name:Ljava/lang/String;
            areturn
        end local 0 // io.netty.handler.codec.mqtt.MqttVersion this
      LocalVariableTable:
        Start  End  Slot  Name  Signature
            0    1     0  this  Lio/netty/handler/codec/mqtt/MqttVersion;

  public byte[] protocolNameBytes();
    descriptor: ()[B
    flags: (0x0001) ACC_PUBLIC
    Code:
      stack=2, locals=1, args_size=1
        start local 0 // io.netty.handler.codec.mqtt.MqttVersion this
         0: .line 42
            aload 0 /* this */
            getfield io.netty.handler.codec.mqtt.MqttVersion.name:Ljava/lang/String;
            getstatic io.netty.util.CharsetUtil.UTF_8:Ljava/nio/charset/Charset;
            invokevirtual java.lang.String.getBytes:(Ljava/nio/charset/Charset;)[B
            areturn
        end local 0 // io.netty.handler.codec.mqtt.MqttVersion this
      LocalVariableTable:
        Start  End  Slot  Name  Signature
            0    1     0  this  Lio/netty/handler/codec/mqtt/MqttVersion;

  public byte protocolLevel();
    descriptor: ()B
    flags: (0x0001) ACC_PUBLIC
    Code:
      stack=1, locals=1, args_size=1
        start local 0 // io.netty.handler.codec.mqtt.MqttVersion this
         0: .line 46
            aload 0 /* this */
            getfield io.netty.handler.codec.mqtt.MqttVersion.level:B
            ireturn
        end local 0 // io.netty.handler.codec.mqtt.MqttVersion this
      LocalVariableTable:
        Start  End  Slot  Name  Signature
            0    1     0  this  Lio/netty/handler/codec/mqtt/MqttVersion;

  public static io.netty.handler.codec.mqtt.MqttVersion fromProtocolNameAndLevel(java.lang.String, byte);
    descriptor: (Ljava/lang/String;B)Lio/netty/handler/codec/mqtt/MqttVersion;
    flags: (0x0009) ACC_PUBLIC, ACC_STATIC
    Code:
      stack=5, locals=6, args_size=2
        start local 0 // java.lang.String protocolName
        start local 1 // byte protocolLevel
         0: .line 50
            invokestatic io.netty.handler.codec.mqtt.MqttVersion.values:()[Lio/netty/handler/codec/mqtt/MqttVersion;
            dup
            astore 5
            arraylength
            istore 4
            iconst_0
            istore 3
            goto 9
      StackMap locals: java.lang.String int top int int io.netty.handler.codec.mqtt.MqttVersion[]
      StackMap stack:
         1: aload 5
            iload 3
            aaload
            astore 2 /* mv */
        start local 2 // io.netty.handler.codec.mqtt.MqttVersion mv
         2: .line 51
            aload 2 /* mv */
            getfield io.netty.handler.codec.mqtt.MqttVersion.name:Ljava/lang/String;
            aload 0 /* protocolName */
            invokevirtual java.lang.String.equals:(Ljava/lang/Object;)Z
            ifeq 8
         3: .line 52
            aload 2 /* mv */
            getfield io.netty.handler.codec.mqtt.MqttVersion.level:B
            iload 1 /* protocolLevel */
            if_icmpne 5
         4: .line 53
            aload 2 /* mv */
            areturn
         5: .line 55
      StackMap locals: java.lang.String int io.netty.handler.codec.mqtt.MqttVersion int int io.netty.handler.codec.mqtt.MqttVersion[]
      StackMap stack:
            new io.netty.handler.codec.mqtt.MqttUnacceptableProtocolVersionException
            dup
            new java.lang.StringBuilder
            dup
            aload 0 /* protocolName */
            invokestatic java.lang.String.valueOf:(Ljava/lang/Object;)Ljava/lang/String;
            invokespecial java.lang.StringBuilder.<init>:(Ljava/lang/String;)V
            ldc " and "
            invokevirtual java.lang.StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder;
         6: .line 56
            iload 1 /* protocolLevel */
            invokevirtual java.lang.StringBuilder.append:(I)Ljava/lang/StringBuilder;
            ldc " are not match"
            invokevirtual java.lang.StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder;
            invokevirtual java.lang.StringBuilder.toString:()Ljava/lang/String;
         7: .line 55
            invokespecial io.netty.handler.codec.mqtt.MqttUnacceptableProtocolVersionException.<init>:(Ljava/lang/String;)V
            athrow
        end local 2 // io.netty.handler.codec.mqtt.MqttVersion mv
         8: .line 50
      StackMap locals: java.lang.String int top int int io.netty.handler.codec.mqtt.MqttVersion[]
      StackMap stack:
            iinc 3 1
      StackMap locals:
      StackMap stack:
         9: iload 3
            iload 4
            if_icmplt 1
        10: .line 60
            new io.netty.handler.codec.mqtt.MqttUnacceptableProtocolVersionException
            dup
            new java.lang.StringBuilder
            dup
            aload 0 /* protocolName */
            invokestatic java.lang.String.valueOf:(Ljava/lang/Object;)Ljava/lang/String;
            invokespecial java.lang.StringBuilder.<init>:(Ljava/lang/String;)V
            ldc "is unknown protocol name"
            invokevirtual java.lang.StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder;
            invokevirtual java.lang.StringBuilder.toString:()Ljava/lang/String;
            invokespecial io.netty.handler.codec.mqtt.MqttUnacceptableProtocolVersionException.<init>:(Ljava/lang/String;)V
            athrow
        end local 1 // byte protocolLevel
        end local 0 // java.lang.String protocolName
      LocalVariableTable:
        Start  End  Slot           Name  Signature
            0   11     0   protocolName  Ljava/lang/String;
            0   11     1  protocolLevel  B
            2    8     2             mv  Lio/netty/handler/codec/mqtt/MqttVersion;
    MethodParameters:
               Name  Flags
      protocolName   
      protocolLevel  

  public static io.netty.handler.codec.mqtt.MqttVersion[] values();
    descriptor: ()[Lio/netty/handler/codec/mqtt/MqttVersion;
    flags: (0x0009) ACC_PUBLIC, ACC_STATIC
    Code:
      stack=5, locals=3, args_size=0
         0: .line 1
            getstatic io.netty.handler.codec.mqtt.MqttVersion.ENUM$VALUES:[Lio/netty/handler/codec/mqtt/MqttVersion;
            dup
            astore 0
            iconst_0
            aload 0
            arraylength
            dup
            istore 1
            anewarray io.netty.handler.codec.mqtt.MqttVersion
            dup
            astore 2
            iconst_0
            iload 1
            invokestatic java.lang.System.arraycopy:(Ljava/lang/Object;ILjava/lang/Object;II)V
            aload 2
            areturn
      LocalVariableTable:
        Start  End  Slot  Name  Signature

  public static io.netty.handler.codec.mqtt.MqttVersion valueOf(java.lang.String);
    descriptor: (Ljava/lang/String;)Lio/netty/handler/codec/mqtt/MqttVersion;
    flags: (0x0009) ACC_PUBLIC, ACC_STATIC
    Code:
      stack=2, locals=1, args_size=1
         0: .line 1
            ldc Lio/netty/handler/codec/mqtt/MqttVersion;
            aload 0
            invokestatic java.lang.Enum.valueOf:(Ljava/lang/Class;Ljava/lang/String;)Ljava/lang/Enum;
            checkcast io.netty.handler.codec.mqtt.MqttVersion
            areturn
      LocalVariableTable:
        Start  End  Slot  Name  Signature
    MethodParameters:
      Name  Flags
      name  
}
Signature: Ljava/lang/Enum<Lio/netty/handler/codec/mqtt/MqttVersion;>;
SourceFile: "MqttVersion.java"