https://lucene.apache.org/lucene-parent/lucene-core: Apache Lucene Java Core (The Apache Software Foundation) 
public class org.apache.lucene.util.CloseableThreadLocal<T> implements java.io.Closeable
  minor version: 0
  major version: 59
  flags: flags: (0x0021) ACC_PUBLIC, ACC_SUPER
  this_class: org.apache.lucene.util.CloseableThreadLocal
  super_class: java.lang.Object
{
  private java.lang.ThreadLocal<java.lang.ref.WeakReference<T>> t;
    descriptor: Ljava/lang/ThreadLocal;
    flags: (0x0002) ACC_PRIVATE
    Signature: Ljava/lang/ThreadLocal<Ljava/lang/ref/WeakReference<TT;>;>;

  private java.util.Map<java.lang.Thread, T> hardRefs;
    descriptor: Ljava/util/Map;
    flags: (0x0002) ACC_PRIVATE
    Signature: Ljava/util/Map<Ljava/lang/Thread;TT;>;

  private static int PURGE_MULTIPLIER;
    descriptor: I
    flags: (0x000a) ACC_PRIVATE, ACC_STATIC

  private final java.util.concurrent.atomic.AtomicInteger countUntilPurge;
    descriptor: Ljava/util/concurrent/atomic/AtomicInteger;
    flags: (0x0012) ACC_PRIVATE, ACC_FINAL

  static void <clinit>();
    descriptor: ()V
    flags: (0x0008) ACC_STATIC
    Code:
      stack=1, locals=0, args_size=0
         0: .line 65
            bipush 20
            putstatic org.apache.lucene.util.CloseableThreadLocal.PURGE_MULTIPLIER:I
            return
      LocalVariableTable:
        Start  End  Slot  Name  Signature

  public void <init>();
    descriptor: ()V
    flags: (0x0001) ACC_PUBLIC
    Code:
      stack=4, locals=1, args_size=1
        start local 0 // org.apache.lucene.util.CloseableThreadLocal this
         0: .line 56
            aload 0 /* this */
            invokespecial java.lang.Object.<init>:()V
         1: .line 58
            aload 0 /* this */
            new java.lang.ThreadLocal
            dup
            invokespecial java.lang.ThreadLocal.<init>:()V
            putfield org.apache.lucene.util.CloseableThreadLocal.t:Ljava/lang/ThreadLocal;
         2: .line 62
            aload 0 /* this */
            new java.util.WeakHashMap
            dup
            invokespecial java.util.WeakHashMap.<init>:()V
            putfield org.apache.lucene.util.CloseableThreadLocal.hardRefs:Ljava/util/Map;
         3: .line 71
            aload 0 /* this */
            new java.util.concurrent.atomic.AtomicInteger
            dup
            getstatic org.apache.lucene.util.CloseableThreadLocal.PURGE_MULTIPLIER:I
            invokespecial java.util.concurrent.atomic.AtomicInteger.<init>:(I)V
            putfield org.apache.lucene.util.CloseableThreadLocal.countUntilPurge:Ljava/util/concurrent/atomic/AtomicInteger;
         4: .line 56
            return
        end local 0 // org.apache.lucene.util.CloseableThreadLocal this
      LocalVariableTable:
        Start  End  Slot  Name  Signature
            0    5     0  this  Lorg/apache/lucene/util/CloseableThreadLocal<TT;>;

  protected T initialValue();
    descriptor: ()Ljava/lang/Object;
    flags: (0x0004) ACC_PROTECTED
    Code:
      stack=1, locals=1, args_size=1
        start local 0 // org.apache.lucene.util.CloseableThreadLocal this
         0: .line 74
            aconst_null
            areturn
        end local 0 // org.apache.lucene.util.CloseableThreadLocal this
      LocalVariableTable:
        Start  End  Slot  Name  Signature
            0    1     0  this  Lorg/apache/lucene/util/CloseableThreadLocal<TT;>;
    Signature: ()TT;

  public T get();
    descriptor: ()Ljava/lang/Object;
    flags: (0x0001) ACC_PUBLIC
    Code:
      stack=2, locals=3, args_size=1
        start local 0 // org.apache.lucene.util.CloseableThreadLocal this
         0: .line 78
            aload 0 /* this */
            getfield org.apache.lucene.util.CloseableThreadLocal.t:Ljava/lang/ThreadLocal;
            invokevirtual java.lang.ThreadLocal.get:()Ljava/lang/Object;
            checkcast java.lang.ref.WeakReference
            astore 1 /* weakRef */
        start local 1 // java.lang.ref.WeakReference weakRef
         1: .line 79
            aload 1 /* weakRef */
            ifnonnull 7
         2: .line 80
            aload 0 /* this */
            invokevirtual org.apache.lucene.util.CloseableThreadLocal.initialValue:()Ljava/lang/Object;
            astore 2 /* iv */
        start local 2 // java.lang.Object iv
         3: .line 81
            aload 2 /* iv */
            ifnull 6
         4: .line 82
            aload 0 /* this */
            aload 2 /* iv */
            invokevirtual org.apache.lucene.util.CloseableThreadLocal.set:(Ljava/lang/Object;)V
         5: .line 83
            aload 2 /* iv */
            areturn
         6: .line 85
      StackMap locals: java.lang.ref.WeakReference java.lang.Object
      StackMap stack:
            aconst_null
            areturn
        end local 2 // java.lang.Object iv
         7: .line 88
      StackMap locals:
      StackMap stack:
            aload 0 /* this */
            invokevirtual org.apache.lucene.util.CloseableThreadLocal.maybePurge:()V
         8: .line 89
            aload 1 /* weakRef */
            invokevirtual java.lang.ref.WeakReference.get:()Ljava/lang/Object;
            areturn
        end local 1 // java.lang.ref.WeakReference weakRef
        end local 0 // org.apache.lucene.util.CloseableThreadLocal this
      LocalVariableTable:
        Start  End  Slot     Name  Signature
            0    9     0     this  Lorg/apache/lucene/util/CloseableThreadLocal<TT;>;
            1    9     1  weakRef  Ljava/lang/ref/WeakReference<TT;>;
            3    7     2       iv  TT;
    Signature: ()TT;

  public void set();
    descriptor: (Ljava/lang/Object;)V
    flags: (0x0001) ACC_PUBLIC
    Code:
      stack=4, locals=3, args_size=2
        start local 0 // org.apache.lucene.util.CloseableThreadLocal this
        start local 1 // java.lang.Object object
         0: .line 95
            aload 0 /* this */
            getfield org.apache.lucene.util.CloseableThreadLocal.t:Ljava/lang/ThreadLocal;
            new java.lang.ref.WeakReference
            dup
            aload 1 /* object */
            invokespecial java.lang.ref.WeakReference.<init>:(Ljava/lang/Object;)V
            invokevirtual java.lang.ThreadLocal.set:(Ljava/lang/Object;)V
         1: .line 97
            aload 0 /* this */
            getfield org.apache.lucene.util.CloseableThreadLocal.hardRefs:Ljava/util/Map;
            dup
            astore 2
            monitorenter
         2: .line 98
            aload 0 /* this */
            getfield org.apache.lucene.util.CloseableThreadLocal.hardRefs:Ljava/util/Map;
            invokestatic java.lang.Thread.currentThread:()Ljava/lang/Thread;
            aload 1 /* object */
            invokeinterface java.util.Map.put:(Ljava/lang/Object;Ljava/lang/Object;)Ljava/lang/Object;
            pop
         3: .line 99
            aload 0 /* this */
            invokevirtual org.apache.lucene.util.CloseableThreadLocal.maybePurge:()V
         4: .line 97
            aload 2
            monitorexit
         5: goto 8
      StackMap locals: org.apache.lucene.util.CloseableThreadLocal java.lang.Object java.util.Map
      StackMap stack: java.lang.Throwable
         6: aload 2
            monitorexit
         7: athrow
         8: .line 101
      StackMap locals:
      StackMap stack:
            return
        end local 1 // java.lang.Object object
        end local 0 // org.apache.lucene.util.CloseableThreadLocal this
      LocalVariableTable:
        Start  End  Slot    Name  Signature
            0    9     0    this  Lorg/apache/lucene/util/CloseableThreadLocal<TT;>;
            0    9     1  object  TT;
      Exception table:
        from    to  target  type
           2     5       6  any
           6     7       6  any
    Signature: (TT;)V
    MethodParameters:
        Name  Flags
      object  

  private void maybePurge();
    descriptor: ()V
    flags: (0x0002) ACC_PRIVATE
    Code:
      stack=1, locals=1, args_size=1
        start local 0 // org.apache.lucene.util.CloseableThreadLocal this
         0: .line 104
            aload 0 /* this */
            getfield org.apache.lucene.util.CloseableThreadLocal.countUntilPurge:Ljava/util/concurrent/atomic/AtomicInteger;
            invokevirtual java.util.concurrent.atomic.AtomicInteger.getAndDecrement:()I
            ifne 2
         1: .line 105
            aload 0 /* this */
            invokevirtual org.apache.lucene.util.CloseableThreadLocal.purge:()V
         2: .line 107
      StackMap locals:
      StackMap stack:
            return
        end local 0 // org.apache.lucene.util.CloseableThreadLocal this
      LocalVariableTable:
        Start  End  Slot  Name  Signature
            0    3     0  this  Lorg/apache/lucene/util/CloseableThreadLocal<TT;>;

  private void purge();
    descriptor: ()V
    flags: (0x0002) ACC_PRIVATE
    Code:
      stack=2, locals=5, args_size=1
        start local 0 // org.apache.lucene.util.CloseableThreadLocal this
         0: .line 111
            aload 0 /* this */
            getfield org.apache.lucene.util.CloseableThreadLocal.hardRefs:Ljava/util/Map;
            dup
            astore 1
            monitorenter
         1: .line 112
            iconst_0
            istore 2 /* stillAliveCount */
        start local 2 // int stillAliveCount
         2: .line 113
            aload 0 /* this */
            getfield org.apache.lucene.util.CloseableThreadLocal.hardRefs:Ljava/util/Map;
            invokeinterface java.util.Map.keySet:()Ljava/util/Set;
            invokeinterface java.util.Set.iterator:()Ljava/util/Iterator;
            astore 3 /* it */
        start local 3 // java.util.Iterator it
         3: goto 9
         4: .line 114
      StackMap locals: java.util.Map int java.util.Iterator
      StackMap stack:
            aload 3 /* it */
            invokeinterface java.util.Iterator.next:()Ljava/lang/Object;
            checkcast java.lang.Thread
            astore 4 /* t */
        start local 4 // java.lang.Thread t
         5: .line 115
            aload 4 /* t */
            invokevirtual java.lang.Thread.isAlive:()Z
            ifne 8
         6: .line 116
            aload 3 /* it */
            invokeinterface java.util.Iterator.remove:()V
         7: .line 117
            goto 9
         8: .line 118
      StackMap locals: java.lang.Thread
      StackMap stack:
            iinc 2 /* stillAliveCount */ 1
        end local 4 // java.lang.Thread t
         9: .line 113
      StackMap locals:
      StackMap stack:
            aload 3 /* it */
            invokeinterface java.util.Iterator.hasNext:()Z
            ifne 4
        end local 3 // java.util.Iterator it
        10: .line 121
            iconst_1
            iload 2 /* stillAliveCount */
            iadd
            getstatic org.apache.lucene.util.CloseableThreadLocal.PURGE_MULTIPLIER:I
            imul
            istore 3 /* nextCount */
        start local 3 // int nextCount
        11: .line 122
            iload 3 /* nextCount */
            ifgt 13
        12: .line 124
            ldc 1000000
            istore 3 /* nextCount */
        13: .line 127
      StackMap locals: org.apache.lucene.util.CloseableThreadLocal java.util.Map int int
      StackMap stack:
            aload 0 /* this */
            getfield org.apache.lucene.util.CloseableThreadLocal.countUntilPurge:Ljava/util/concurrent/atomic/AtomicInteger;
            iload 3 /* nextCount */
            invokevirtual java.util.concurrent.atomic.AtomicInteger.set:(I)V
        end local 3 // int nextCount
        end local 2 // int stillAliveCount
        14: .line 111
            aload 1
            monitorexit
        15: goto 18
      StackMap locals: org.apache.lucene.util.CloseableThreadLocal java.util.Map
      StackMap stack: java.lang.Throwable
        16: aload 1
            monitorexit
        17: athrow
        18: .line 129
      StackMap locals:
      StackMap stack:
            return
        end local 0 // org.apache.lucene.util.CloseableThreadLocal this
      LocalVariableTable:
        Start  End  Slot             Name  Signature
            0   19     0             this  Lorg/apache/lucene/util/CloseableThreadLocal<TT;>;
            2   14     2  stillAliveCount  I
            3   10     3               it  Ljava/util/Iterator<Ljava/lang/Thread;>;
            5    9     4                t  Ljava/lang/Thread;
           11   14     3        nextCount  I
      Exception table:
        from    to  target  type
           1    15      16  any
          16    17      16  any

  public void close();
    descriptor: ()V
    flags: (0x0001) ACC_PUBLIC
    Code:
      stack=2, locals=1, args_size=1
        start local 0 // org.apache.lucene.util.CloseableThreadLocal this
         0: .line 136
            aload 0 /* this */
            aconst_null
            putfield org.apache.lucene.util.CloseableThreadLocal.hardRefs:Ljava/util/Map;
         1: .line 139
            aload 0 /* this */
            getfield org.apache.lucene.util.CloseableThreadLocal.t:Ljava/lang/ThreadLocal;
            ifnull 3
         2: .line 140
            aload 0 /* this */
            getfield org.apache.lucene.util.CloseableThreadLocal.t:Ljava/lang/ThreadLocal;
            invokevirtual java.lang.ThreadLocal.remove:()V
         3: .line 142
      StackMap locals:
      StackMap stack:
            aload 0 /* this */
            aconst_null
            putfield org.apache.lucene.util.CloseableThreadLocal.t:Ljava/lang/ThreadLocal;
         4: .line 143
            return
        end local 0 // org.apache.lucene.util.CloseableThreadLocal this
      LocalVariableTable:
        Start  End  Slot  Name  Signature
            0    5     0  this  Lorg/apache/lucene/util/CloseableThreadLocal<TT;>;
}
Signature: <T:Ljava/lang/Object;>Ljava/lang/Object;Ljava/io/Closeable;
SourceFile: "CloseableThreadLocal.java"