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.Functions$IntegerPassThruFunction implements org.eclipse.collections.api.block.function.Function<java.lang.Integer, java.lang.Integer>, org.eclipse.collections.api.block.function.primitive.IntFunction<java.lang.Integer>
  minor version: 0
  major version: 59
  flags: flags: (0x0020) ACC_SUPER
  this_class: org.eclipse.collections.impl.block.factory.Functions$IntegerPassThruFunction
  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.Functions$IntegerPassThruFunction this
         0: .line 689
            aload 0 /* this */
            invokespecial java.lang.Object.<init>:()V
            return
        end local 0 // org.eclipse.collections.impl.block.factory.Functions$IntegerPassThruFunction this
      LocalVariableTable:
        Start  End  Slot  Name  Signature
            0    1     0  this  Lorg/eclipse/collections/impl/block/factory/Functions$IntegerPassThruFunction;

  public int intValueOf(java.lang.Integer);
    descriptor: (Ljava/lang/Integer;)I
    flags: (0x0001) ACC_PUBLIC
    Code:
      stack=1, locals=2, args_size=2
        start local 0 // org.eclipse.collections.impl.block.factory.Functions$IntegerPassThruFunction this
        start local 1 // java.lang.Integer each
         0: .line 696
            aload 1 /* each */
            invokevirtual java.lang.Integer.intValue:()I
            ireturn
        end local 1 // java.lang.Integer each
        end local 0 // org.eclipse.collections.impl.block.factory.Functions$IntegerPassThruFunction this
      LocalVariableTable:
        Start  End  Slot  Name  Signature
            0    1     0  this  Lorg/eclipse/collections/impl/block/factory/Functions$IntegerPassThruFunction;
            0    1     1  each  Ljava/lang/Integer;
    MethodParameters:
      Name  Flags
      each  

  public java.lang.Integer valueOf(java.lang.Integer);
    descriptor: (Ljava/lang/Integer;)Ljava/lang/Integer;
    flags: (0x0001) ACC_PUBLIC
    Code:
      stack=1, locals=2, args_size=2
        start local 0 // org.eclipse.collections.impl.block.factory.Functions$IntegerPassThruFunction this
        start local 1 // java.lang.Integer each
         0: .line 702
            aload 1 /* each */
            areturn
        end local 1 // java.lang.Integer each
        end local 0 // org.eclipse.collections.impl.block.factory.Functions$IntegerPassThruFunction this
      LocalVariableTable:
        Start  End  Slot  Name  Signature
            0    1     0  this  Lorg/eclipse/collections/impl/block/factory/Functions$IntegerPassThruFunction;
            0    1     1  each  Ljava/lang/Integer;
    MethodParameters:
      Name  Flags
      each  

  public java.lang.String toString();
    descriptor: ()Ljava/lang/String;
    flags: (0x0001) ACC_PUBLIC
    Code:
      stack=1, locals=1, args_size=1
        start local 0 // org.eclipse.collections.impl.block.factory.Functions$IntegerPassThruFunction this
         0: .line 708
            ldc Lorg/eclipse/collections/impl/block/factory/Functions$IntegerPassThruFunction;
            invokevirtual java.lang.Class.getSimpleName:()Ljava/lang/String;
            areturn
        end local 0 // org.eclipse.collections.impl.block.factory.Functions$IntegerPassThruFunction this
      LocalVariableTable:
        Start  End  Slot  Name  Signature
            0    1     0  this  Lorg/eclipse/collections/impl/block/factory/Functions$IntegerPassThruFunction;

  public int intValueOf(java.lang.Object);
    descriptor: (Ljava/lang/Object;)I
    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.Functions$IntegerPassThruFunction.intValueOf:(Ljava/lang/Integer;)I
            ireturn
      LocalVariableTable:
        Start  End  Slot  Name  Signature

  public java.lang.Object valueOf(java.lang.Object);
    descriptor: (Ljava/lang/Object;)Ljava/lang/Object;
    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.Functions$IntegerPassThruFunction.valueOf:(Ljava/lang/Integer;)Ljava/lang/Integer;
            areturn
      LocalVariableTable:
        Start  End  Slot  Name  Signature
}
Signature: Ljava/lang/Object;Lorg/eclipse/collections/api/block/function/Function<Ljava/lang/Integer;Ljava/lang/Integer;>;Lorg/eclipse/collections/api/block/function/primitive/IntFunction<Ljava/lang/Integer;>;
SourceFile: "Functions.java"
NestHost: org.eclipse.collections.impl.block.factory.Functions
InnerClasses:
  private IntegerPassThruFunction = org.eclipse.collections.impl.block.factory.Functions$IntegerPassThruFunction of org.eclipse.collections.impl.block.factory.Functions