https://www.graalvm.org/ 
final class com.oracle.truffle.polyglot.PolyglotEngineImpl$LogConfig
  minor version: 0
  major version: 59
  flags: flags: (0x0030) ACC_FINAL, ACC_SUPER
  this_class: com.oracle.truffle.polyglot.PolyglotEngineImpl$LogConfig
  super_class: java.lang.Object
{
  final java.util.Map<java.lang.String, java.util.logging.Level> logLevels;
    descriptor: Ljava/util/Map;
    flags: (0x0010) ACC_FINAL
    Signature: Ljava/util/Map<Ljava/lang/String;Ljava/util/logging/Level;>;

  java.lang.String logFile;
    descriptor: Ljava/lang/String;
    flags: (0x0000) 

  void <init>();
    descriptor: ()V
    flags: (0x0000) 
    Code:
      stack=3, locals=1, args_size=1
        start local 0 // com.oracle.truffle.polyglot.PolyglotEngineImpl$LogConfig this
         0: .line 1900
            aload 0 /* this */
            invokespecial java.lang.Object.<init>:()V
         1: .line 1901
            aload 0 /* this */
            new java.util.HashMap
            dup
            invokespecial java.util.HashMap.<init>:()V
            putfield com.oracle.truffle.polyglot.PolyglotEngineImpl$LogConfig.logLevels:Ljava/util/Map;
         2: .line 1902
            return
        end local 0 // com.oracle.truffle.polyglot.PolyglotEngineImpl$LogConfig this
      LocalVariableTable:
        Start  End  Slot  Name  Signature
            0    3     0  this  Lcom/oracle/truffle/polyglot/PolyglotEngineImpl$LogConfig;
}
SourceFile: "PolyglotEngineImpl.java"
NestHost: com.oracle.truffle.polyglot.PolyglotEngineImpl
InnerClasses:
  final LogConfig = com.oracle.truffle.polyglot.PolyglotEngineImpl$LogConfig of com.oracle.truffle.polyglot.PolyglotEngineImpl