This is a small library that is used in many of my projects.
x590.util - general util classes
x590.util.io - some Input/Output classes
x590.util.annotation - annotations, including Nullable and Notnull
x590.util.function - addition to java.util.function. Contains functional interfaces that are not in the standard library.
x590.util.holder - classes that contain values of primitives or objects. It is used, for example, when you need to change the value of a local variable from a lambda
x590.util.lazyloading - contains classes for deferred loading of various types (including primitives).
JavaSE 16