I first generate a specification JSON object from a text design narrative that lists fine-grained steps for each Java class that are constrained to be decomposed such that each fine grained step can be implemented as a static method in 20 lines of Java code or less. Likewise helper methods are similarly scoped to 20 LOC or less.

I also have a markdown-formatted document `core-programming-guidelines.md` that I include in the Claude Code code-generation prompt.

For example:

## Core Programming Principles

### Defensive Programming & Safety 1. *Use 'final' keyword aggressively* for method parameters, local variables, and class fields 2. *Null Safety*: Include null checks with Validate.notNull() and assertions for external calls 3. *Input Validation*: Validate all method parameters with clear preconditions using org.apache.commons.lang3.Validate

### Performance Optimization 1. *Collection Sizing*: Always provide calculated initial capacity for collections 2. *String Processing*: Use StringBuilder with pre-calculated capacity, avoid regex where possible and avoid `java.util.Scanner` where possible. 3. *Memory Management*: Clear large collections when done, reuse objects where appropriate

### Code Clarity & Documentation 1. *Naming Conventions*: Use descriptive names for variables, methods, and constants - All StringBuilder variables should be suffixed `Builder`. 2. *Documentation*: Comprehensive JavaDoc for all public, protected, and private methods 3. *Inline Comments*: Explain complex logic, algorithms, and business rules

### Modern Java 23 Features 1. *Text Blocks*: Use for multi-line string literals 2. *Pattern Matching*: Use where appropriate for cleaner code 3. *Records*: Use for immutable data carriers 4. *Enhanced Switch*: Use new switch expressions