https://freemarker.apache.org/: FreeMarker is a "template engine"; a generic tool to generate text output based on templates. (Apache Software Foundation) 
public abstract class freemarker.ext.util.ModelCache
  minor version: 0
  major version: 59
  flags: flags: (0x0421) ACC_PUBLIC, ACC_SUPER, ACC_ABSTRACT
  this_class: freemarker.ext.util.ModelCache
  super_class: java.lang.Object
{
  private boolean useCache;
    descriptor: Z
    flags: (0x0002) ACC_PRIVATE

  private java.util.Map<java.lang.Object, freemarker.ext.util.ModelCache$ModelReference> modelCache;
    descriptor: Ljava/util/Map;
    flags: (0x0002) ACC_PRIVATE
    Signature: Ljava/util/Map<Ljava/lang/Object;Lfreemarker/ext/util/ModelCache$ModelReference;>;

  private java.lang.ref.ReferenceQueue<freemarker.template.TemplateModel> refQueue;
    descriptor: Ljava/lang/ref/ReferenceQueue;
    flags: (0x0002) ACC_PRIVATE
    Signature: Ljava/lang/ref/ReferenceQueue<Lfreemarker/template/TemplateModel;>;

  protected void <init>();
    descriptor: ()V
    flags: (0x0004) ACC_PROTECTED
    Code:
      stack=2, locals=1, args_size=1
        start local 0 // freemarker.ext.util.ModelCache this
         0: .line 39
            aload 0 /* this */
            invokespecial java.lang.Object.<init>:()V
         1: .line 35
            aload 0 /* this */
            iconst_0
            putfield freemarker.ext.util.ModelCache.useCache:Z
         2: .line 36
            aload 0 /* this */
            aconst_null
            putfield freemarker.ext.util.ModelCache.modelCache:Ljava/util/Map;
         3: .line 37
            aload 0 /* this */
            aconst_null
            putfield freemarker.ext.util.ModelCache.refQueue:Ljava/lang/ref/ReferenceQueue;
         4: .line 40
            return
        end local 0 // freemarker.ext.util.ModelCache this
      LocalVariableTable:
        Start  End  Slot  Name  Signature
            0    5     0  this  Lfreemarker/ext/util/ModelCache;

  public synchronized void setUseCache(boolean);
    descriptor: (Z)V
    flags: (0x0021) ACC_PUBLIC, ACC_SYNCHRONIZED
    Code:
      stack=3, locals=2, args_size=2
        start local 0 // freemarker.ext.util.ModelCache this
        start local 1 // boolean useCache
         0: .line 48
            aload 0 /* this */
            iload 1 /* useCache */
            putfield freemarker.ext.util.ModelCache.useCache:Z
         1: .line 49
            iload 1 /* useCache */
            ifeq 5
         2: .line 50
            aload 0 /* this */
            new java.util.IdentityHashMap
            dup
            invokespecial java.util.IdentityHashMap.<init>:()V
            putfield freemarker.ext.util.ModelCache.modelCache:Ljava/util/Map;
         3: .line 51
            aload 0 /* this */
            new java.lang.ref.ReferenceQueue
            dup
            invokespecial java.lang.ref.ReferenceQueue.<init>:()V
            putfield freemarker.ext.util.ModelCache.refQueue:Ljava/lang/ref/ReferenceQueue;
         4: .line 52
            goto 7
         5: .line 53
      StackMap locals:
      StackMap stack:
            aload 0 /* this */
            aconst_null
            putfield freemarker.ext.util.ModelCache.modelCache:Ljava/util/Map;
         6: .line 54
            aload 0 /* this */
            aconst_null
            putfield freemarker.ext.util.ModelCache.refQueue:Ljava/lang/ref/ReferenceQueue;
         7: .line 56
      StackMap locals:
      StackMap stack:
            return
        end local 1 // boolean useCache
        end local 0 // freemarker.ext.util.ModelCache this
      LocalVariableTable:
        Start  End  Slot      Name  Signature
            0    8     0      this  Lfreemarker/ext/util/ModelCache;
            0    8     1  useCache  Z
    MethodParameters:
          Name  Flags
      useCache  

  public synchronized boolean getUseCache();
    descriptor: ()Z
    flags: (0x0021) ACC_PUBLIC, ACC_SYNCHRONIZED
    Code:
      stack=1, locals=1, args_size=1
        start local 0 // freemarker.ext.util.ModelCache this
         0: .line 62
            aload 0 /* this */
            getfield freemarker.ext.util.ModelCache.useCache:Z
            ireturn
        end local 0 // freemarker.ext.util.ModelCache this
      LocalVariableTable:
        Start  End  Slot  Name  Signature
            0    1     0  this  Lfreemarker/ext/util/ModelCache;

  public freemarker.template.TemplateModel getInstance(java.lang.Object);
    descriptor: (Ljava/lang/Object;)Lfreemarker/template/TemplateModel;
    flags: (0x0001) ACC_PUBLIC
    Code:
      stack=3, locals=3, args_size=2
        start local 0 // freemarker.ext.util.ModelCache this
        start local 1 // java.lang.Object object
         0: .line 66
            aload 1 /* object */
            instanceof freemarker.template.TemplateModel
            ifeq 2
         1: .line 67
            aload 1 /* object */
            checkcast freemarker.template.TemplateModel
            areturn
         2: .line 69
      StackMap locals:
      StackMap stack:
            aload 1 /* object */
            instanceof freemarker.template.TemplateModelAdapter
            ifeq 4
         3: .line 70
            aload 1 /* object */
            checkcast freemarker.template.TemplateModelAdapter
            invokeinterface freemarker.template.TemplateModelAdapter.getTemplateModel:()Lfreemarker/template/TemplateModel;
            areturn
         4: .line 72
      StackMap locals:
      StackMap stack:
            aload 0 /* this */
            getfield freemarker.ext.util.ModelCache.useCache:Z
            ifeq 10
            aload 0 /* this */
            aload 1 /* object */
            invokevirtual freemarker.ext.util.ModelCache.isCacheable:(Ljava/lang/Object;)Z
            ifeq 10
         5: .line 73
            aload 0 /* this */
            aload 1 /* object */
            invokevirtual freemarker.ext.util.ModelCache.lookup:(Ljava/lang/Object;)Lfreemarker/template/TemplateModel;
            astore 2 /* model */
        start local 2 // freemarker.template.TemplateModel model
         6: .line 74
            aload 2 /* model */
            ifnonnull 9
         7: .line 75
            aload 0 /* this */
            aload 1 /* object */
            invokevirtual freemarker.ext.util.ModelCache.create:(Ljava/lang/Object;)Lfreemarker/template/TemplateModel;
            astore 2 /* model */
         8: .line 76
            aload 0 /* this */
            aload 2 /* model */
            aload 1 /* object */
            invokevirtual freemarker.ext.util.ModelCache.register:(Lfreemarker/template/TemplateModel;Ljava/lang/Object;)V
         9: .line 78
      StackMap locals: freemarker.template.TemplateModel
      StackMap stack:
            aload 2 /* model */
            areturn
        end local 2 // freemarker.template.TemplateModel model
        10: .line 80
      StackMap locals:
      StackMap stack:
            aload 0 /* this */
            aload 1 /* object */
            invokevirtual freemarker.ext.util.ModelCache.create:(Ljava/lang/Object;)Lfreemarker/template/TemplateModel;
            areturn
        end local 1 // java.lang.Object object
        end local 0 // freemarker.ext.util.ModelCache this
      LocalVariableTable:
        Start  End  Slot    Name  Signature
            0   11     0    this  Lfreemarker/ext/util/ModelCache;
            0   11     1  object  Ljava/lang/Object;
            6   10     2   model  Lfreemarker/template/TemplateModel;
    MethodParameters:
        Name  Flags
      object  

  protected abstract freemarker.template.TemplateModel create(java.lang.Object);
    descriptor: (Ljava/lang/Object;)Lfreemarker/template/TemplateModel;
    flags: (0x0404) ACC_PROTECTED, ACC_ABSTRACT
    MethodParameters:
        Name  Flags
      object  

  protected abstract boolean isCacheable(java.lang.Object);
    descriptor: (Ljava/lang/Object;)Z
    flags: (0x0404) ACC_PROTECTED, ACC_ABSTRACT
    MethodParameters:
        Name  Flags
      object  

  public void clearCache();
    descriptor: ()V
    flags: (0x0001) ACC_PUBLIC
    Code:
      stack=2, locals=2, args_size=1
        start local 0 // freemarker.ext.util.ModelCache this
         0: .line 88
            aload 0 /* this */
            getfield freemarker.ext.util.ModelCache.modelCache:Ljava/util/Map;
            ifnull 7
         1: .line 89
            aload 0 /* this */
            getfield freemarker.ext.util.ModelCache.modelCache:Ljava/util/Map;
            dup
            astore 1
            monitorenter
         2: .line 90
            aload 0 /* this */
            getfield freemarker.ext.util.ModelCache.modelCache:Ljava/util/Map;
            invokeinterface java.util.Map.clear:()V
         3: .line 89
            aload 1
            monitorexit
         4: goto 7
      StackMap locals: freemarker.ext.util.ModelCache java.util.Map
      StackMap stack: java.lang.Throwable
         5: aload 1
            monitorexit
         6: athrow
         7: .line 93
      StackMap locals:
      StackMap stack:
            return
        end local 0 // freemarker.ext.util.ModelCache this
      LocalVariableTable:
        Start  End  Slot  Name  Signature
            0    8     0  this  Lfreemarker/ext/util/ModelCache;
      Exception table:
        from    to  target  type
           2     4       5  any
           5     6       5  any

  private final freemarker.template.TemplateModel lookup(java.lang.Object);
    descriptor: (Ljava/lang/Object;)Lfreemarker/template/TemplateModel;
    flags: (0x0012) ACC_PRIVATE, ACC_FINAL
    Code:
      stack=2, locals=4, args_size=2
        start local 0 // freemarker.ext.util.ModelCache this
        start local 1 // java.lang.Object object
         0: .line 96
            aconst_null
            astore 2 /* ref */
        start local 2 // freemarker.ext.util.ModelCache$ModelReference ref
         1: .line 100
            aload 0 /* this */
            getfield freemarker.ext.util.ModelCache.modelCache:Ljava/util/Map;
            dup
            astore 3
            monitorenter
         2: .line 101
            aload 0 /* this */
            getfield freemarker.ext.util.ModelCache.modelCache:Ljava/util/Map;
            aload 1 /* object */
            invokeinterface java.util.Map.get:(Ljava/lang/Object;)Ljava/lang/Object;
            checkcast freemarker.ext.util.ModelCache$ModelReference
            astore 2 /* ref */
         3: .line 100
            aload 3
            monitorexit
         4: goto 7
      StackMap locals: freemarker.ext.util.ModelCache java.lang.Object freemarker.ext.util.ModelCache$ModelReference java.util.Map
      StackMap stack: java.lang.Throwable
         5: aload 3
            monitorexit
         6: athrow
         7: .line 104
      StackMap locals:
      StackMap stack:
            aload 2 /* ref */
            ifnull 9
         8: .line 105
            aload 2 /* ref */
            invokevirtual freemarker.ext.util.ModelCache$ModelReference.getModel:()Lfreemarker/template/TemplateModel;
            areturn
         9: .line 107
      StackMap locals:
      StackMap stack:
            aconst_null
            areturn
        end local 2 // freemarker.ext.util.ModelCache$ModelReference ref
        end local 1 // java.lang.Object object
        end local 0 // freemarker.ext.util.ModelCache this
      LocalVariableTable:
        Start  End  Slot    Name  Signature
            0   10     0    this  Lfreemarker/ext/util/ModelCache;
            0   10     1  object  Ljava/lang/Object;
            1   10     2     ref  Lfreemarker/ext/util/ModelCache$ModelReference;
      Exception table:
        from    to  target  type
           2     4       5  any
           5     6       5  any
    MethodParameters:
        Name  Flags
      object  

  private final void register(freemarker.template.TemplateModel, java.lang.Object);
    descriptor: (Lfreemarker/template/TemplateModel;Ljava/lang/Object;)V
    flags: (0x0012) ACC_PRIVATE, ACC_FINAL
    Code:
      stack=7, locals=5, args_size=3
        start local 0 // freemarker.ext.util.ModelCache this
        start local 1 // freemarker.template.TemplateModel model
        start local 2 // java.lang.Object object
         0: .line 111
            aload 0 /* this */
            getfield freemarker.ext.util.ModelCache.modelCache:Ljava/util/Map;
            dup
            astore 3
            monitorenter
         1: .line 114
      StackMap locals: java.util.Map
      StackMap stack:
            aload 0 /* this */
            getfield freemarker.ext.util.ModelCache.refQueue:Ljava/lang/ref/ReferenceQueue;
            invokevirtual java.lang.ref.ReferenceQueue.poll:()Ljava/lang/ref/Reference;
            checkcast freemarker.ext.util.ModelCache$ModelReference
            astore 4 /* queuedRef */
        start local 4 // freemarker.ext.util.ModelCache$ModelReference queuedRef
         2: .line 115
            aload 4 /* queuedRef */
            ifnonnull 4
         3: .line 116
            goto 6
         4: .line 118
      StackMap locals: freemarker.ext.util.ModelCache$ModelReference
      StackMap stack:
            aload 0 /* this */
            getfield freemarker.ext.util.ModelCache.modelCache:Ljava/util/Map;
            aload 4 /* queuedRef */
            getfield freemarker.ext.util.ModelCache$ModelReference.object:Ljava/lang/Object;
            invokeinterface java.util.Map.remove:(Ljava/lang/Object;)Ljava/lang/Object;
            pop
        end local 4 // freemarker.ext.util.ModelCache$ModelReference queuedRef
         5: .line 113
            goto 1
         6: .line 121
      StackMap locals:
      StackMap stack:
            aload 0 /* this */
            getfield freemarker.ext.util.ModelCache.modelCache:Ljava/util/Map;
            aload 2 /* object */
            new freemarker.ext.util.ModelCache$ModelReference
            dup
            aload 1 /* model */
            aload 2 /* object */
            aload 0 /* this */
            getfield freemarker.ext.util.ModelCache.refQueue:Ljava/lang/ref/ReferenceQueue;
            invokespecial freemarker.ext.util.ModelCache$ModelReference.<init>:(Lfreemarker/template/TemplateModel;Ljava/lang/Object;Ljava/lang/ref/ReferenceQueue;)V
            invokeinterface java.util.Map.put:(Ljava/lang/Object;Ljava/lang/Object;)Ljava/lang/Object;
            pop
         7: .line 111
            aload 3
            monitorexit
         8: goto 11
      StackMap locals:
      StackMap stack: java.lang.Throwable
         9: aload 3
            monitorexit
        10: athrow
        11: .line 123
      StackMap locals:
      StackMap stack:
            return
        end local 2 // java.lang.Object object
        end local 1 // freemarker.template.TemplateModel model
        end local 0 // freemarker.ext.util.ModelCache this
      LocalVariableTable:
        Start  End  Slot       Name  Signature
            0   12     0       this  Lfreemarker/ext/util/ModelCache;
            0   12     1      model  Lfreemarker/template/TemplateModel;
            0   12     2     object  Ljava/lang/Object;
            2    5     4  queuedRef  Lfreemarker/ext/util/ModelCache$ModelReference;
      Exception table:
        from    to  target  type
           1     8       9  any
           9    10       9  any
    MethodParameters:
        Name  Flags
      model   
      object  
}
SourceFile: "ModelCache.java"
NestMembers:
  freemarker.ext.util.ModelCache$ModelReference
InnerClasses:
  private final ModelReference = freemarker.ext.util.ModelCache$ModelReference of freemarker.ext.util.ModelCache