https://www.graalvm.org/ 
class com.oracle.truffle.api.instrumentation.test.ContextsEventsTest$1 implements java.lang.Runnable
  minor version: 0
  major version: 59
  flags: flags: (0x0020) ACC_SUPER
  this_class: com.oracle.truffle.api.instrumentation.test.ContextsEventsTest$1
  super_class: java.lang.Object
{
  final com.oracle.truffle.api.instrumentation.test.ContextsEventsTest this$0;
    descriptor: Lcom/oracle/truffle/api/instrumentation/test/ContextsEventsTest;
    flags: (0x1010) ACC_FINAL, ACC_SYNTHETIC

  private final org.graalvm.polyglot.Engine val$engine;
    descriptor: Lorg/graalvm/polyglot/Engine;
    flags: (0x1012) ACC_PRIVATE, ACC_FINAL, ACC_SYNTHETIC

  private final com.oracle.truffle.api.instrumentation.test.ThreadsEventsTest$TestBlockOnStatementsInstrument val$testBlock;
    descriptor: Lcom/oracle/truffle/api/instrumentation/test/ThreadsEventsTest$TestBlockOnStatementsInstrument;
    flags: (0x1012) ACC_PRIVATE, ACC_FINAL, ACC_SYNTHETIC

  void <init>(com.oracle.truffle.api.instrumentation.test.ContextsEventsTest, org.graalvm.polyglot.Engine, com.oracle.truffle.api.instrumentation.test.ThreadsEventsTest$TestBlockOnStatementsInstrument);
    descriptor: (Lcom/oracle/truffle/api/instrumentation/test/ContextsEventsTest;Lorg/graalvm/polyglot/Engine;Lcom/oracle/truffle/api/instrumentation/test/ThreadsEventsTest$TestBlockOnStatementsInstrument;)V
    flags: (0x0000) 
    Code:
      stack=2, locals=4, args_size=4
        start local 0 // com.oracle.truffle.api.instrumentation.test.ContextsEventsTest$1 this
         0: .line 235
            aload 0 /* this */
            aload 1
            putfield com.oracle.truffle.api.instrumentation.test.ContextsEventsTest$1.this$0:Lcom/oracle/truffle/api/instrumentation/test/ContextsEventsTest;
            aload 0 /* this */
            aload 2
            putfield com.oracle.truffle.api.instrumentation.test.ContextsEventsTest$1.val$engine:Lorg/graalvm/polyglot/Engine;
            aload 0 /* this */
            aload 3
            putfield com.oracle.truffle.api.instrumentation.test.ContextsEventsTest$1.val$testBlock:Lcom/oracle/truffle/api/instrumentation/test/ThreadsEventsTest$TestBlockOnStatementsInstrument;
            aload 0 /* this */
            invokespecial java.lang.Object.<init>:()V
            return
        end local 0 // com.oracle.truffle.api.instrumentation.test.ContextsEventsTest$1 this
      LocalVariableTable:
        Start  End  Slot  Name  Signature
            0    1     0  this  Lcom/oracle/truffle/api/instrumentation/test/ContextsEventsTest$1;
    MethodParameters:
               Name  Flags
      this$0         final
      val$engine     final
      val$testBlock  final

  public void run();
    descriptor: ()V
    flags: (0x0001) ACC_PUBLIC
    Code:
      stack=4, locals=4, args_size=1
        start local 0 // com.oracle.truffle.api.instrumentation.test.ContextsEventsTest$1 this
         0: .line 240
            aload 0 /* this */
            getfield com.oracle.truffle.api.instrumentation.test.ContextsEventsTest$1.val$engine:Lorg/graalvm/polyglot/Engine;
            invokevirtual org.graalvm.polyglot.Engine.getInstruments:()Ljava/util/Map;
            ldc "testContexsInstrument"
            invokeinterface java.util.Map.get:(Ljava/lang/Object;)Ljava/lang/Object;
            checkcast org.graalvm.polyglot.Instrument
            astore 1 /* testContexsInstrument */
        start local 1 // org.graalvm.polyglot.Instrument testContexsInstrument
         1: .line 241
            aload 1 /* testContexsInstrument */
            ldc Lcom/oracle/truffle/api/instrumentation/test/ContextsEventsTest$TestContextsInstrument;
            invokevirtual org.graalvm.polyglot.Instrument.lookup:(Ljava/lang/Class;)Ljava/lang/Object;
            checkcast com.oracle.truffle.api.instrumentation.test.ContextsEventsTest$TestContextsInstrument
            astore 2 /* test */
        start local 2 // com.oracle.truffle.api.instrumentation.test.ContextsEventsTest$TestContextsInstrument test
         2: .line 242
            aload 2 /* test */
            getfield com.oracle.truffle.api.instrumentation.test.ContextsEventsTest$TestContextsInstrument.events:Ljava/util/List;
            astore 3 /* events */
        start local 3 // java.util.List events
         3: .line 243
            ldc 3
            aload 3 /* events */
            invokeinterface java.util.List.size:()I
            i2l
            invokestatic org.junit.Assert.assertEquals:(JJ)V
         4: .line 244
            aload 3 /* events */
            iconst_0
            invokeinterface java.util.List.get:(I)Ljava/lang/Object;
            checkcast com.oracle.truffle.api.instrumentation.test.ContextsEventsTest$ContextEvent
            getfield com.oracle.truffle.api.instrumentation.test.ContextsEventsTest$ContextEvent.created:Z
            invokestatic org.junit.Assert.assertTrue:(Z)V
         5: .line 245
            aload 3 /* events */
            iconst_0
            invokeinterface java.util.List.get:(I)Ljava/lang/Object;
            checkcast com.oracle.truffle.api.instrumentation.test.ContextsEventsTest$ContextEvent
            getfield com.oracle.truffle.api.instrumentation.test.ContextsEventsTest$ContextEvent.language:Lcom/oracle/truffle/api/nodes/LanguageInfo;
            invokestatic org.junit.Assert.assertNull:(Ljava/lang/Object;)V
         6: .line 246
            aload 3 /* events */
            iconst_1
            invokeinterface java.util.List.get:(I)Ljava/lang/Object;
            checkcast com.oracle.truffle.api.instrumentation.test.ContextsEventsTest$ContextEvent
            getfield com.oracle.truffle.api.instrumentation.test.ContextsEventsTest$ContextEvent.created:Z
            invokestatic org.junit.Assert.assertTrue:(Z)V
         7: .line 247
            ldc "instrumentation-test-language"
            aload 3 /* events */
            iconst_1
            invokeinterface java.util.List.get:(I)Ljava/lang/Object;
            checkcast com.oracle.truffle.api.instrumentation.test.ContextsEventsTest$ContextEvent
            getfield com.oracle.truffle.api.instrumentation.test.ContextsEventsTest$ContextEvent.language:Lcom/oracle/truffle/api/nodes/LanguageInfo;
            invokevirtual com.oracle.truffle.api.nodes.LanguageInfo.getId:()Ljava/lang/String;
            invokestatic org.junit.Assert.assertEquals:(Ljava/lang/Object;Ljava/lang/Object;)V
         8: .line 248
            aload 3 /* events */
            iconst_2
            invokeinterface java.util.List.get:(I)Ljava/lang/Object;
            checkcast com.oracle.truffle.api.instrumentation.test.ContextsEventsTest$ContextEvent
            getfield com.oracle.truffle.api.instrumentation.test.ContextsEventsTest$ContextEvent.languageInitialized:Z
            invokestatic org.junit.Assert.assertTrue:(Z)V
         9: .line 249
            aload 0 /* this */
            getfield com.oracle.truffle.api.instrumentation.test.ContextsEventsTest$1.val$testBlock:Lcom/oracle/truffle/api/instrumentation/test/ThreadsEventsTest$TestBlockOnStatementsInstrument;
            getfield com.oracle.truffle.api.instrumentation.test.ThreadsEventsTest$TestBlockOnStatementsInstrument.blockOnStatements:Ljava/util/concurrent/atomic/AtomicBoolean;
            iconst_0
            invokevirtual java.util.concurrent.atomic.AtomicBoolean.set:(Z)V
        10: .line 250
            return
        end local 3 // java.util.List events
        end local 2 // com.oracle.truffle.api.instrumentation.test.ContextsEventsTest$TestContextsInstrument test
        end local 1 // org.graalvm.polyglot.Instrument testContexsInstrument
        end local 0 // com.oracle.truffle.api.instrumentation.test.ContextsEventsTest$1 this
      LocalVariableTable:
        Start  End  Slot                   Name  Signature
            0   11     0                   this  Lcom/oracle/truffle/api/instrumentation/test/ContextsEventsTest$1;
            1   11     1  testContexsInstrument  Lorg/graalvm/polyglot/Instrument;
            2   11     2                   test  Lcom/oracle/truffle/api/instrumentation/test/ContextsEventsTest$TestContextsInstrument;
            3   11     3                 events  Ljava/util/List<Lcom/oracle/truffle/api/instrumentation/test/ContextsEventsTest$ContextEvent;>;
}
SourceFile: "ContextsEventsTest.java"
EnclosingMethod: com.oracle.truffle.api.instrumentation.test.ContextsEventsTest.testGetActiveContexts:()V
NestHost: com.oracle.truffle.api.instrumentation.test.ContextsEventsTest
InnerClasses:
  com.oracle.truffle.api.instrumentation.test.ContextsEventsTest$1
  private ContextEvent = com.oracle.truffle.api.instrumentation.test.ContextsEventsTest$ContextEvent of com.oracle.truffle.api.instrumentation.test.ContextsEventsTest
  public TestContextsInstrument = com.oracle.truffle.api.instrumentation.test.ContextsEventsTest$TestContextsInstrument of com.oracle.truffle.api.instrumentation.test.ContextsEventsTest
  public TestBlockOnStatementsInstrument = com.oracle.truffle.api.instrumentation.test.ThreadsEventsTest$TestBlockOnStatementsInstrument of com.oracle.truffle.api.instrumentation.test.ThreadsEventsTest