Using Java 8 Functional Interfaces to Simplify Conditional Logic

In Java development, excessive use of if...else... statements can make code messy; Java 8 functional interfaces provide a cleaner alternative.

The @FunctionalInterface annotation marks interfaces with a single abstract method, such as Supplier (no arguments, returns a value), Consumer (accepts an argument, returns void), Runnable (no arguments, no return), and Function (accepts an argument and returns a value).

A custom functional interface ThrowExceptionFunction is defined to encapsulate exception‑throwing logic, with a static helper method isTure that returns an instance which throws a RuntimeException when the supplied boolean is true.

Another interface BranchHandle abstracts true/false branching by accepting two Runnable actions; the static method isTureOrFalse returns a lambda that executes the appropriate runnable based on the boolean condition.

The PresentOrElseHandler interface handles optional values by taking a Consumer for non‑null values and a Runnable for null/empty cases; the static method isBlankOrNoBlank implements this logic for strings.

These patterns demonstrate how functional interfaces can replace repetitive if...else blocks, improve readability, and simplify exception and branch handling in backend Java code.