https://www.graalvm.org/ 
class org.graalvm.component.installer.remote.FileDownloaderTest$FA extends org.graalvm.component.installer.TestBase$FeedbackAdapter
  minor version: 0
  major version: 59
  flags: flags: (0x0020) ACC_SUPER
  this_class: org.graalvm.component.installer.remote.FileDownloaderTest$FA
  super_class: org.graalvm.component.installer.TestBase$FeedbackAdapter
{
  final org.graalvm.component.installer.remote.FileDownloaderTest this$0;
    descriptor: Lorg/graalvm/component/installer/remote/FileDownloaderTest;
    flags: (0x1010) ACC_FINAL, ACC_SYNTHETIC

  void <init>(org.graalvm.component.installer.remote.FileDownloaderTest);
    descriptor: (Lorg/graalvm/component/installer/remote/FileDownloaderTest;)V
    flags: (0x0000) 
    Code:
      stack=2, locals=2, args_size=2
        start local 0 // org.graalvm.component.installer.remote.FileDownloaderTest$FA this
         0: .line 50
            aload 0 /* this */
            aload 1
            putfield org.graalvm.component.installer.remote.FileDownloaderTest$FA.this$0:Lorg/graalvm/component/installer/remote/FileDownloaderTest;
            aload 0 /* this */
            aload 1
            invokespecial org.graalvm.component.installer.TestBase$FeedbackAdapter.<init>:(Lorg/graalvm/component/installer/TestBase;)V
            return
        end local 0 // org.graalvm.component.installer.remote.FileDownloaderTest$FA this
      LocalVariableTable:
        Start  End  Slot  Name  Signature
            0    1     0  this  Lorg/graalvm/component/installer/remote/FileDownloaderTest$FA;
    MethodParameters:
        Name  Flags
      this$0  final

  public java.lang.String l10n(java.lang.String, java.lang.Object[]);
    descriptor: (Ljava/lang/String;[Ljava/lang/Object;)Ljava/lang/String;
    flags: (0x0081) ACC_PUBLIC, ACC_VARARGS
    Code:
      stack=2, locals=4, args_size=3
        start local 0 // org.graalvm.component.installer.remote.FileDownloaderTest$FA this
        start local 1 // java.lang.String key
        start local 2 // java.lang.Object[] params
         0: .line 54
            aload 1 /* key */
            dup
            astore 3
            invokevirtual java.lang.String.hashCode:()I
            lookupswitch { // 2
           -136146291: 1
           1267281178: 2
              default: 5
          }
      StackMap locals: java.lang.String
      StackMap stack:
         1: aload 3
            ldc "MSG_DownloadProgress@"
            invokevirtual java.lang.String.equals:(Ljava/lang/Object;)Z
            ifne 3
            goto 5
      StackMap locals:
      StackMap stack:
         2: aload 3
            ldc "MSG_DownloadProgressSignChar@"
            invokevirtual java.lang.String.equals:(Ljava/lang/Object;)Z
            ifne 4
            goto 5
         3: .line 56
      StackMap locals:
      StackMap stack:
            ldc "[                    ]"
            areturn
         4: .line 58
      StackMap locals:
      StackMap stack:
            ldc "#"
            areturn
         5: .line 60
      StackMap locals:
      StackMap stack:
            aload 1 /* key */
            areturn
        end local 2 // java.lang.Object[] params
        end local 1 // java.lang.String key
        end local 0 // org.graalvm.component.installer.remote.FileDownloaderTest$FA this
      LocalVariableTable:
        Start  End  Slot    Name  Signature
            0    6     0    this  Lorg/graalvm/component/installer/remote/FileDownloaderTest$FA;
            0    6     1     key  Ljava/lang/String;
            0    6     2  params  [Ljava/lang/Object;
    MethodParameters:
        Name  Flags
      key     
      params  
}
SourceFile: "FileDownloaderTest.java"
NestHost: org.graalvm.component.installer.remote.FileDownloaderTest
InnerClasses:
  public FeedbackAdapter = org.graalvm.component.installer.TestBase$FeedbackAdapter of org.graalvm.component.installer.TestBase
  FA = org.graalvm.component.installer.remote.FileDownloaderTest$FA of org.graalvm.component.installer.remote.FileDownloaderTest