https://github.com/eclipse/eclipse-collections/eclipse-collections-api: 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 
public interface org.eclipse.collections.api.block.function.primitive.DoubleFunction0 extends java.util.function.DoubleSupplier, java.io.Serializable
  minor version: 0
  major version: 59
  flags: flags: (0x0601) ACC_PUBLIC, ACC_INTERFACE, ACC_ABSTRACT
  this_class: org.eclipse.collections.api.block.function.primitive.DoubleFunction0
  super_class: java.lang.Object
{
  public abstract double value();
    descriptor: ()D
    flags: (0x0401) ACC_PUBLIC, ACC_ABSTRACT

  public double getAsDouble();
    descriptor: ()D
    flags: (0x0001) ACC_PUBLIC
    Code:
      stack=2, locals=1, args_size=1
        start local 0 // org.eclipse.collections.api.block.function.primitive.DoubleFunction0 this
         0: .line 32
            aload 0 /* this */
            invokeinterface org.eclipse.collections.api.block.function.primitive.DoubleFunction0.value:()D
            dreturn
        end local 0 // org.eclipse.collections.api.block.function.primitive.DoubleFunction0 this
      LocalVariableTable:
        Start  End  Slot  Name  Signature
            0    1     0  this  Lorg/eclipse/collections/api/block/function/primitive/DoubleFunction0;
}
SourceFile: "DoubleFunction0.java"
    RuntimeVisibleAnnotations: 
      java.lang.FunctionalInterface()