https://github.com/eclipse/eclipse-collections/eclipse-collections: Eclipse Collections is a collections framework for Java. It has JDK-compatible List, Set and Map implementations with a rich API and set of utility classes that work with any JDK compatible Collections, Arrays, Maps or Strings. The iteration protocol was inspired by the Smalltalk collection framework.
  • Craig P. Motlin
  • Donald Raab
  • Mohammad A. Rezaei
  • Hiroshi Ito
  • Nikhil J. Nanivadekar 
class org.eclipse.collections.impl.block.factory.PrimitiveFunctions$UnboxIntegerToDouble implements org.eclipse.collections.api.block.function.primitive.DoubleFunction<java.lang.Integer>
  minor version: 0
  major version: 59
  flags: flags: (0x0020) ACC_SUPER
  this_class: org.eclipse.collections.impl.block.factory.PrimitiveFunctions$UnboxIntegerToDouble
  super_class: java.lang.Object
{
  private static final long serialVersionUID;
    descriptor: J
    flags: (0x001a) ACC_PRIVATE, ACC_STATIC, ACC_FINAL
    ConstantValue: 1

  private void <init>();
    descriptor: ()V
    flags: (0x0002) ACC_PRIVATE
    Code:
      stack=1, locals=1, args_size=1
        start local 0 // org.eclipse.collections.impl.block.factory.PrimitiveFunctions$UnboxIntegerToDouble this
         0: .line 283
            aload 0 /* this */
            invokespecial java.lang.Object.<init>:()V
            return
        end local 0 // org.eclipse.collections.impl.block.factory.PrimitiveFunctions$UnboxIntegerToDouble this
      LocalVariableTable:
        Start  End  Slot  Name  Signature
            0    1     0  this  Lorg/eclipse/collections/impl/block/factory/PrimitiveFunctions$UnboxIntegerToDouble;

  public double doubleValueOf(java.lang.Integer);
    descriptor: (Ljava/lang/Integer;)D
    flags: (0x0001) ACC_PUBLIC
    Code:
      stack=2, locals=2, args_size=2
        start local 0 // org.eclipse.collections.impl.block.factory.PrimitiveFunctions$UnboxIntegerToDouble this
        start local 1 // java.lang.Integer integer
         0: .line 291
            aload 1 /* integer */
            invokevirtual java.lang.Integer.intValue:()I
            i2d
            dreturn
        end local 1 // java.lang.Integer integer
        end local 0 // org.eclipse.collections.impl.block.factory.PrimitiveFunctions$UnboxIntegerToDouble this
      LocalVariableTable:
        Start  End  Slot     Name  Signature
            0    1     0     this  Lorg/eclipse/collections/impl/block/factory/PrimitiveFunctions$UnboxIntegerToDouble;
            0    1     1  integer  Ljava/lang/Integer;
    MethodParameters:
         Name  Flags
      integer  

  public double doubleValueOf(java.lang.Object);
    descriptor: (Ljava/lang/Object;)D
    flags: (0x1041) ACC_PUBLIC, ACC_BRIDGE, ACC_SYNTHETIC
    Code:
      stack=2, locals=2, args_size=2
         0: .line 1
            aload 0
            aload 1
            checkcast java.lang.Integer
            invokevirtual org.eclipse.collections.impl.block.factory.PrimitiveFunctions$UnboxIntegerToDouble.doubleValueOf:(Ljava/lang/Integer;)D
            dreturn
      LocalVariableTable:
        Start  End  Slot  Name  Signature
}
Signature: Ljava/lang/Object;Lorg/eclipse/collections/api/block/function/primitive/DoubleFunction<Ljava/lang/Integer;>;
SourceFile: "PrimitiveFunctions.java"
NestHost: org.eclipse.collections.impl.block.factory.PrimitiveFunctions
InnerClasses:
  private UnboxIntegerToDouble = org.eclipse.collections.impl.block.factory.PrimitiveFunctions$UnboxIntegerToDouble of org.eclipse.collections.impl.block.factory.PrimitiveFunctions