https://www.graalvm.org/ 
class org.graalvm.compiler.core.test.ConcreteSubtypeTest$Subclass extends org.graalvm.compiler.core.test.ConcreteSubtypeTest$AbstractBase
  minor version: 0
  major version: 59
  flags: flags: (0x0020) ACC_SUPER
  this_class: org.graalvm.compiler.core.test.ConcreteSubtypeTest$Subclass
  super_class: org.graalvm.compiler.core.test.ConcreteSubtypeTest$AbstractBase
{
  void <init>();
    descriptor: ()V
    flags: (0x0000) 
    Code:
      stack=1, locals=1, args_size=1
        start local 0 // org.graalvm.compiler.core.test.ConcreteSubtypeTest$Subclass this
         0: .line 40
            aload 0 /* this */
            invokespecial org.graalvm.compiler.core.test.ConcreteSubtypeTest$AbstractBase.<init>:()V
            return
        end local 0 // org.graalvm.compiler.core.test.ConcreteSubtypeTest$Subclass this
      LocalVariableTable:
        Start  End  Slot  Name  Signature
            0    1     0  this  Lorg/graalvm/compiler/core/test/ConcreteSubtypeTest$Subclass;

  public void check();
    descriptor: ()V
    flags: (0x0001) ACC_PUBLIC
    Code:
      stack=2, locals=1, args_size=1
        start local 0 // org.graalvm.compiler.core.test.ConcreteSubtypeTest$Subclass this
         0: .line 43
            new java.lang.InternalError
            dup
            invokespecial java.lang.InternalError.<init>:()V
            athrow
        end local 0 // org.graalvm.compiler.core.test.ConcreteSubtypeTest$Subclass this
      LocalVariableTable:
        Start  End  Slot  Name  Signature
            0    1     0  this  Lorg/graalvm/compiler/core/test/ConcreteSubtypeTest$Subclass;
}
SourceFile: "ConcreteSubtypeTest.java"
NestHost: org.graalvm.compiler.core.test.ConcreteSubtypeTest
InnerClasses:
  abstract AbstractBase = org.graalvm.compiler.core.test.ConcreteSubtypeTest$AbstractBase of org.graalvm.compiler.core.test.ConcreteSubtypeTest
  Subclass = org.graalvm.compiler.core.test.ConcreteSubtypeTest$Subclass of org.graalvm.compiler.core.test.ConcreteSubtypeTest