Java Fluency for Backend Code

Write an immutable Java domain class with validated constructor arguments.

Use interfaces and constructor-based composition to implement a small service.

Select an appropriate Java collection based on ordering, uniqueness, and lookup requirements.

Implement the equals and hashCode contract for an object used in hash-based collections.

Use generics to make a small Java API type-safe.

Transform a collection with lambdas and streams while explaining when a loop is clearer.

Model and handle a failure using Java exceptions without suppressing useful diagnostic information.

Explain how a Java build tool resolves dependencies and produces a runnable artifact.