131-java-refactoring-with-modern-features

Guidance for using Java 8 and newer language and library features, such as lambdas, streams, Optional, modern date handling, immutable collections, and asynchronous tasks.

In plain words
What is it for?
Use it when refactoring Java code, handling missing values and dates, processing collections, evolving interfaces, or adopting features from newer Java versions.
Why use it?
It helps replace older, repetitive patterns with clearer code while accounting for readability, testing, and performance.

Cursor rule for Cursor

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add rules/alkoleft/platform-context-exporter/131-java-refactoring-with-modern-features
Clone the repo
git clone --depth 1 https://github.com/alkoleft/platform-context-exporter

Made for: Cursor.

Per session 0 Nothing until a file matches its globs; then the whole rule loads.
When invoked 12,523 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5 $0.00000 $0.12523
Opus 5 $0.00000 $0.06262
Sonnet 5 $0.00000 $0.02505
Haiku 4.5 $0.00000 $0.01252

Measured 3d ago against content hash 022eab9fb769, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

131-java-refactoring-with-modern-features scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 3d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

.cursor/rules/131-java-refactoring-with-modern-features.mdc · 1,265 lines

How it starts

The opening of the file, as written. The whole thing — 1,265 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Modern Java Development Guidelines (Java 8+)

Modern Java development (Java 8+) emphasizes leveraging lambda expressions and functional interfaces over anonymous classes, and using the Stream API for declarative collection processing. The Optional API should be used for handling potentially absent values gracefully, and the java.time API for all date/time operations. Default methods allow non-breaking interface evolution. Local Variable Type Inference (var) can improve readability when used judiciously. Unmodifiable collection factory methods (List.of(), etc.) provide concise immutable collections. CompletableFuture facilitates composable asynchronous programming. The Java Platform Module System (JPMS, Java 9+) enables strong encapsulation. Performance implications of new features should be considered and profiled. Testing strategies need to adapt to these modern features, and text blocks (Java 15+) offer improved readability for multi-line strings.

Implementing These Principles

These guidelines are built upon the following core principles:

  1. Conciseness and Readability: Leverage modern Java features (like lambdas, streams, var, text blocks) to write code that is more concise and easier to read and understand, reducing boilerplate and focusing on intent.
  2. Immutability and Safety: Embrace features like Optional, unmodifiable collection factories, and the java.time API to create more robust, null-safe, and thread-safe code by default, reducing common sources of bugs.
  3. Expressive Power: Utilize functional constructs like streams and CompletableFuture to express complex data manipulations and asynchronous workflows in a more declarative and composable manner.
  4. Asynchronous and Modular Design: Employ CompletableFuture for efficient asynchronous programming and the Java Platform Module System (JPMS) for building maintainable, strongly encapsulated applications with clear dependencies.
  5. Performance Awareness: While modern features offer syntactic improvements, remain mindful of their potential performance implications. Profile critical sections and make informed decisions, especially with streams and asynchronous operations.

Read the full file on GitHub · 1,265 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 3d ago First seen · 1,265 lines · 12,523 tokens per session scan A 022eab9fb769

Subscribe to this mod's changes

131-java-refactoring-with-modern-features is a cursor rule published in the GitHub repository alkoleft/platform-context-exporter (48 stars, last pushed 1y ago), licensed MIT. It costs nothing until one of its globs matches a file; then it loads 12,523 tokens. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.