https://github.com/Terracotta-OSS/offheap-store/: A library that offers data structures allocated off the java heap. 
public class org.terracotta.offheapstore.disk.persistent.AbstractPersistentConcurrentOffHeapCache<K, V> extends org.terracotta.offheapstore.concurrent.AbstractConcurrentOffHeapCache<K, V> implements org.terracotta.offheapstore.disk.persistent.Persistent
  minor version: 0
  major version: 59
  flags: flags: (0x0021) ACC_PUBLIC, ACC_SUPER
  this_class: org.terracotta.offheapstore.disk.persistent.AbstractPersistentConcurrentOffHeapCache
  super_class: org.terracotta.offheapstore.concurrent.AbstractConcurrentOffHeapCache
{
  private static final int MAGIC;
    descriptor: I
    flags: (0x001a) ACC_PRIVATE, ACC_STATIC, ACC_FINAL
    ConstantValue: 1463898953

  public void <init>(org.terracotta.offheapstore.util.Factory<? extends org.terracotta.offheapstore.pinning.PinnableSegment<K, V>>);
    descriptor: (Lorg/terracotta/offheapstore/util/Factory;)V
    flags: (0x0001) ACC_PUBLIC
    Code:
      stack=2, locals=2, args_size=2
        start local 0 // org.terracotta.offheapstore.disk.persistent.AbstractPersistentConcurrentOffHeapCache this
        start local 1 // org.terracotta.offheapstore.util.Factory segmentFactory
         0: .line 40
            aload 0 /* this */
            aload 1 /* segmentFactory */
            invokespecial org.terracotta.offheapstore.concurrent.AbstractConcurrentOffHeapCache.<init>:(Lorg/terracotta/offheapstore/util/Factory;)V
         1: .line 41
            return
        end local 1 // org.terracotta.offheapstore.util.Factory segmentFactory
        end local 0 // org.terracotta.offheapstore.disk.persistent.AbstractPersistentConcurrentOffHeapCache this
      LocalVariableTable:
        Start  End  Slot            Name  Signature
            0    2     0            this  Lorg/terracotta/offheapstore/disk/persistent/AbstractPersistentConcurrentOffHeapCache<TK;TV;>;
            0    2     1  segmentFactory  Lorg/terracotta/offheapstore/util/Factory<+Lorg/terracotta/offheapstore/pinning/PinnableSegment<TK;TV;>;>;
    Signature: (Lorg/terracotta/offheapstore/util/Factory<+Lorg/terracotta/offheapstore/pinning/PinnableSegment<TK;TV;>;>;)V
    MethodParameters:
                Name  Flags
      segmentFactory  

  public void <init>(org.terracotta.offheapstore.util.Factory<? extends org.terracotta.offheapstore.pinning.PinnableSegment<K, V>>, );
    descriptor: (Lorg/terracotta/offheapstore/util/Factory;I)V
    flags: (0x0001) ACC_PUBLIC
    Code:
      stack=3, locals=3, args_size=3
        start local 0 // org.terracotta.offheapstore.disk.persistent.AbstractPersistentConcurrentOffHeapCache this
        start local 1 // org.terracotta.offheapstore.util.Factory segmentFactory
        start local 2 // int concurrency
         0: .line 52
            aload 0 /* this */
            aload 1 /* segmentFactory */
            iload 2 /* concurrency */
            invokespecial org.terracotta.offheapstore.concurrent.AbstractConcurrentOffHeapCache.<init>:(Lorg/terracotta/offheapstore/util/Factory;I)V
         1: .line 53
            return
        end local 2 // int concurrency
        end local 1 // org.terracotta.offheapstore.util.Factory segmentFactory
        end local 0 // org.terracotta.offheapstore.disk.persistent.AbstractPersistentConcurrentOffHeapCache this
      LocalVariableTable:
        Start  End  Slot            Name  Signature
            0    2     0            this  Lorg/terracotta/offheapstore/disk/persistent/AbstractPersistentConcurrentOffHeapCache<TK;TV;>;
            0    2     1  segmentFactory  Lorg/terracotta/offheapstore/util/Factory<+Lorg/terracotta/offheapstore/pinning/PinnableSegment<TK;TV;>;>;
            0    2     2     concurrency  I
    Signature: (Lorg/terracotta/offheapstore/util/Factory<+Lorg/terracotta/offheapstore/pinning/PinnableSegment<TK;TV;>;>;I)V
    MethodParameters:
                Name  Flags
      segmentFactory  
      concurrency     

  public void flush();
    descriptor: ()V
    flags: (0x0001) ACC_PUBLIC
    Code:
      stack=2, locals=5, args_size=1
        start local 0 // org.terracotta.offheapstore.disk.persistent.AbstractPersistentConcurrentOffHeapCache this
         0: .line 57
            aload 0 /* this */
            getfield org.terracotta.offheapstore.disk.persistent.AbstractPersistentConcurrentOffHeapCache.segments:[Lorg/terracotta/offheapstore/Segment;
            dup
            astore 4
            arraylength
            istore 3
            iconst_0
            istore 2
            goto 4
      StackMap locals: org.terracotta.offheapstore.disk.persistent.AbstractPersistentConcurrentOffHeapCache top int int org.terracotta.offheapstore.Segment[]
      StackMap stack:
         1: aload 4
            iload 2
            aaload
            astore 1 /* s */
        start local 1 // org.terracotta.offheapstore.Segment s
         2: .line 58
            aload 1 /* s */
            checkcast org.terracotta.offheapstore.disk.persistent.Persistent
            invokeinterface org.terracotta.offheapstore.disk.persistent.Persistent.flush:()V
        end local 1 // org.terracotta.offheapstore.Segment s
         3: .line 57
            iinc 2 1
      StackMap locals:
      StackMap stack:
         4: iload 2
            iload 3
            if_icmplt 1
         5: .line 60
            return
        end local 0 // org.terracotta.offheapstore.disk.persistent.AbstractPersistentConcurrentOffHeapCache this
      LocalVariableTable:
        Start  End  Slot  Name  Signature
            0    6     0  this  Lorg/terracotta/offheapstore/disk/persistent/AbstractPersistentConcurrentOffHeapCache<TK;TV;>;
            2    3     1     s  Lorg/terracotta/offheapstore/Segment<**>;
    Exceptions:
      throws java.io.IOException

  public void persist(java.io.ObjectOutput);
    descriptor: (Ljava/io/ObjectOutput;)V
    flags: (0x0001) ACC_PUBLIC
    Code:
      stack=2, locals=6, args_size=2
        start local 0 // org.terracotta.offheapstore.disk.persistent.AbstractPersistentConcurrentOffHeapCache this
        start local 1 // java.io.ObjectOutput output
         0: .line 64
            aload 1 /* output */
            ldc 1463898953
            invokeinterface java.io.ObjectOutput.writeInt:(I)V
         1: .line 65
            aload 1 /* output */
            aload 0 /* this */
            getfield org.terracotta.offheapstore.disk.persistent.AbstractPersistentConcurrentOffHeapCache.segments:[Lorg/terracotta/offheapstore/Segment;
            arraylength
            invokeinterface java.io.ObjectOutput.writeInt:(I)V
         2: .line 66
            aload 0 /* this */
            getfield org.terracotta.offheapstore.disk.persistent.AbstractPersistentConcurrentOffHeapCache.segments:[Lorg/terracotta/offheapstore/Segment;
            dup
            astore 5
            arraylength
            istore 4
            iconst_0
            istore 3
            goto 6
      StackMap locals: org.terracotta.offheapstore.disk.persistent.AbstractPersistentConcurrentOffHeapCache java.io.ObjectOutput top int int org.terracotta.offheapstore.Segment[]
      StackMap stack:
         3: aload 5
            iload 3
            aaload
            astore 2 /* s */
        start local 2 // org.terracotta.offheapstore.Segment s
         4: .line 67
            aload 2 /* s */
            checkcast org.terracotta.offheapstore.disk.persistent.Persistent
            aload 1 /* output */
            invokeinterface org.terracotta.offheapstore.disk.persistent.Persistent.persist:(Ljava/io/ObjectOutput;)V
        end local 2 // org.terracotta.offheapstore.Segment s
         5: .line 66
            iinc 3 1
      StackMap locals:
      StackMap stack:
         6: iload 3
            iload 4
            if_icmplt 3
         7: .line 69
            return
        end local 1 // java.io.ObjectOutput output
        end local 0 // org.terracotta.offheapstore.disk.persistent.AbstractPersistentConcurrentOffHeapCache this
      LocalVariableTable:
        Start  End  Slot    Name  Signature
            0    8     0    this  Lorg/terracotta/offheapstore/disk/persistent/AbstractPersistentConcurrentOffHeapCache<TK;TV;>;
            0    8     1  output  Ljava/io/ObjectOutput;
            4    5     2       s  Lorg/terracotta/offheapstore/Segment<**>;
    Exceptions:
      throws java.io.IOException
    MethodParameters:
        Name  Flags
      output  

  public void close();
    descriptor: ()V
    flags: (0x0001) ACC_PUBLIC
    Code:
      stack=2, locals=5, args_size=1
        start local 0 // org.terracotta.offheapstore.disk.persistent.AbstractPersistentConcurrentOffHeapCache this
         0: .line 73
            aload 0 /* this */
            getfield org.terracotta.offheapstore.disk.persistent.AbstractPersistentConcurrentOffHeapCache.segments:[Lorg/terracotta/offheapstore/Segment;
            dup
            astore 4
            arraylength
            istore 3
            iconst_0
            istore 2
            goto 4
      StackMap locals: org.terracotta.offheapstore.disk.persistent.AbstractPersistentConcurrentOffHeapCache top int int org.terracotta.offheapstore.Segment[]
      StackMap stack:
         1: aload 4
            iload 2
            aaload
            astore 1 /* s */
        start local 1 // org.terracotta.offheapstore.Segment s
         2: .line 74
            aload 1 /* s */
            checkcast org.terracotta.offheapstore.disk.persistent.Persistent
            invokeinterface org.terracotta.offheapstore.disk.persistent.Persistent.close:()V
        end local 1 // org.terracotta.offheapstore.Segment s
         3: .line 73
            iinc 2 1
      StackMap locals:
      StackMap stack:
         4: iload 2
            iload 3
            if_icmplt 1
         5: .line 76
            return
        end local 0 // org.terracotta.offheapstore.disk.persistent.AbstractPersistentConcurrentOffHeapCache this
      LocalVariableTable:
        Start  End  Slot  Name  Signature
            0    6     0  this  Lorg/terracotta/offheapstore/disk/persistent/AbstractPersistentConcurrentOffHeapCache<TK;TV;>;
            2    3     1     s  Lorg/terracotta/offheapstore/Segment<**>;
    Exceptions:
      throws java.io.IOException

  public void bootstrap(java.io.ObjectInput);
    descriptor: (Ljava/io/ObjectInput;)V
    flags: (0x0001) ACC_PUBLIC
    Code:
      stack=2, locals=6, args_size=2
        start local 0 // org.terracotta.offheapstore.disk.persistent.AbstractPersistentConcurrentOffHeapCache this
        start local 1 // java.io.ObjectInput input
         0: .line 80
            aload 0 /* this */
            getfield org.terracotta.offheapstore.disk.persistent.AbstractPersistentConcurrentOffHeapCache.segments:[Lorg/terracotta/offheapstore/Segment;
            dup
            astore 5
            arraylength
            istore 4
            iconst_0
            istore 3
            goto 4
      StackMap locals: org.terracotta.offheapstore.disk.persistent.AbstractPersistentConcurrentOffHeapCache java.io.ObjectInput top int int org.terracotta.offheapstore.Segment[]
      StackMap stack:
         1: aload 5
            iload 3
            aaload
            astore 2 /* s */
        start local 2 // org.terracotta.offheapstore.Segment s
         2: .line 81
            aload 2 /* s */
            checkcast org.terracotta.offheapstore.disk.persistent.Persistent
            aload 1 /* input */
            invokeinterface org.terracotta.offheapstore.disk.persistent.Persistent.bootstrap:(Ljava/io/ObjectInput;)V
        end local 2 // org.terracotta.offheapstore.Segment s
         3: .line 80
            iinc 3 1
      StackMap locals:
      StackMap stack:
         4: iload 3
            iload 4
            if_icmplt 1
         5: .line 83
            return
        end local 1 // java.io.ObjectInput input
        end local 0 // org.terracotta.offheapstore.disk.persistent.AbstractPersistentConcurrentOffHeapCache this
      LocalVariableTable:
        Start  End  Slot   Name  Signature
            0    6     0   this  Lorg/terracotta/offheapstore/disk/persistent/AbstractPersistentConcurrentOffHeapCache<TK;TV;>;
            0    6     1  input  Ljava/io/ObjectInput;
            2    3     2      s  Lorg/terracotta/offheapstore/Segment<**>;
    Exceptions:
      throws java.io.IOException
    MethodParameters:
       Name  Flags
      input  

  protected static int readSegmentCount(java.io.ObjectInput);
    descriptor: (Ljava/io/ObjectInput;)I
    flags: (0x000c) ACC_PROTECTED, ACC_STATIC
    Code:
      stack=3, locals=1, args_size=1
        start local 0 // java.io.ObjectInput input
         0: .line 86
            aload 0 /* input */
            invokeinterface java.io.ObjectInput.readInt:()I
            ldc 1463898953
            if_icmpeq 2
         1: .line 87
            new java.io.IOException
            dup
            ldc "Wrong magic number"
            invokespecial java.io.IOException.<init>:(Ljava/lang/String;)V
            athrow
         2: .line 89
      StackMap locals:
      StackMap stack:
            aload 0 /* input */
            invokeinterface java.io.ObjectInput.readInt:()I
            ireturn
        end local 0 // java.io.ObjectInput input
      LocalVariableTable:
        Start  End  Slot   Name  Signature
            0    3     0  input  Ljava/io/ObjectInput;
    Exceptions:
      throws java.io.IOException
    MethodParameters:
       Name  Flags
      input  
}
Signature: <K:Ljava/lang/Object;V:Ljava/lang/Object;>Lorg/terracotta/offheapstore/concurrent/AbstractConcurrentOffHeapCache<TK;TV;>;Lorg/terracotta/offheapstore/disk/persistent/Persistent;
SourceFile: "AbstractPersistentConcurrentOffHeapCache.java"