https://www.graalvm.org/ 
class com.oracle.truffle.api.test.polyglot.ContextAPITest$1CollectibleThread extends java.lang.Thread
  minor version: 0
  major version: 59
  flags: flags: (0x0020) ACC_SUPER
  this_class: com.oracle.truffle.api.test.polyglot.ContextAPITest$1CollectibleThread
  super_class: java.lang.Thread
{
  final com.oracle.truffle.api.test.polyglot.ContextAPITest this$0;
    descriptor: Lcom/oracle/truffle/api/test/polyglot/ContextAPITest;
    flags: (0x1010) ACC_FINAL, ACC_SYNTHETIC

  void <init>(com.oracle.truffle.api.test.polyglot.ContextAPITest, java.lang.Runnable, int[]);
    descriptor: (Lcom/oracle/truffle/api/test/polyglot/ContextAPITest;Ljava/lang/Runnable;[I)V
    flags: (0x0000) 
    Code:
      stack=8, locals=4, args_size=4
        start local 0 // com.oracle.truffle.api.test.polyglot.ContextAPITest$1CollectibleThread this
        start local 2 // java.lang.Runnable target
         0: .line 572
            aload 0 /* this */
            aload 1
            putfield com.oracle.truffle.api.test.polyglot.ContextAPITest$1CollectibleThread.this$0:Lcom/oracle/truffle/api/test/polyglot/ContextAPITest;
         1: .line 573
            aload 0 /* this */
            aload 2 /* target */
            new java.lang.StringBuilder
            dup
            ldc "pool-"
            invokespecial java.lang.StringBuilder.<init>:(Ljava/lang/String;)V
            aload 3
            iconst_0
            dup2
            iaload
            dup_x2
            iconst_1
            iadd
            iastore
            invokevirtual java.lang.StringBuilder.append:(I)Ljava/lang/StringBuilder;
            invokevirtual java.lang.StringBuilder.toString:()Ljava/lang/String;
            invokespecial java.lang.Thread.<init>:(Ljava/lang/Runnable;Ljava/lang/String;)V
         2: .line 574
            return
        end local 2 // java.lang.Runnable target
        end local 0 // com.oracle.truffle.api.test.polyglot.ContextAPITest$1CollectibleThread this
      LocalVariableTable:
        Start  End  Slot    Name  Signature
            0    3     0    this  Lcom/oracle/truffle/api/test/polyglot/ContextAPITest$1CollectibleThread;
            0    3     2  target  Ljava/lang/Runnable;
    MethodParameters:
             Name  Flags
      this$0       final
      target       
      val$counter  final
}
SourceFile: "ContextAPITest.java"
EnclosingMethod: com.oracle.truffle.api.test.polyglot.ContextAPITest.lambda$22:([ILjava/util/Set;Ljava/lang/Runnable;)Ljava/lang/Thread;
NestHost: com.oracle.truffle.api.test.polyglot.ContextAPITest
InnerClasses:
  CollectibleThread = com.oracle.truffle.api.test.polyglot.ContextAPITest$1CollectibleThread