Algebraic Data Types + Pattern Matching = Elegant and readable Java code

What if the compiler could guarantee your code handles every possible case? Learn how sealed types and pattern matching bring this power to modern Java.

#1about 2 minutes

Introducing the 'SEND + MORE = MONEY' puzzle

A cryptarithmetic puzzle is presented where letters represent unique digits in a mathematical equation that must be solved.

#2about 3 minutes

Designing a solver and defining an expression grammar

A high-level solution is designed with a generator and evaluator, based on a grammar that defines expressions as constants, variables, additions, or multiplications.

#3about 4 minutes

Understanding algebraic data types and pattern matching in Java

Product types are implemented with records and sum types with sealed interfaces, which can then be deconstructed using pattern matching for `instanceof` and `switch`.

#4about 2 minutes

Modeling expressions as an algebraic data type

An expression is modeled as a sum type using a Java sealed interface with record implementations for constant, variable, addition, and multiplication.

#5about 3 minutes

Implementing an evaluation function with pattern matching

A static `evaluate` function uses a pattern matching switch expression to recursively calculate the value of an expression tree, ensuring compile-time safety.

#6about 8 minutes

Building the puzzle solver and constraints

The main puzzle solver logic is built by creating a sealed interface for constraints and using a generator to check all combinations against them.

#7about 4 minutes

Assembling and running the puzzle solution test

A unit test is created to assemble the puzzle's variables, expressions, and constraints, which is then run to find and verify the final solution.

#8about 1 minute

The pattern of data-oriented programming in Java

The combination of algebraic data types for data modeling and pattern matching for behavior is defined as data-oriented programming, a powerful pattern for writing readable code.