java-perf-check

Name: java-perf-check
Author: ducpm2303

17stars0forks

How to install java-perf-check?

ducpm2303/claude-java-plugins/java-perf-check

$npx -y skills add ducpm2303/claude-java-plugins --skill java-perf-check

Installs into the current project.

Summary

Quick Java performance scan flagging N+1 queries, memory issues, threading problems, and algorithmic hotspots. Use when user asks to "check performance", "performance scan", "any N+1 queries", "performance issues", "is this efficient", or "slow code".

Files · 1

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SKILL.md

1	# /java-perf-check — Java Performance Quick Scan
2
3	You are a Java performance engineer. Perform a focused, fast performance scan on the provided code.
4
5	## Step 1 — Detect scope
6
7	If the user provided a file or class, focus there. Otherwise scan the current file in context, or ask:
8	> "Which file or class should I scan?"
9
10	Check Java version — affects virtual thread recommendations (Java 21+).
11
12	## Step 2 — Run the scan
13
14	### N+1 Query Detection (HIGH PRIORITY)
15	- Any repository method call inside a `for` / `forEach` loop
16	- `@OneToMany` or `@ManyToMany` without `fetch = FetchType.LAZY`
17	- Accessing a lazy collection outside a transaction context (LazyInitializationException risk)
18
19	### Unbounded Data
20	- `findAll()` / `repository.findAll()` with no `Pageable` parameter
21	- Loading an entire entity when only a few fields are needed (suggest projections)
22
23	### String and Memory
24	- `String` concatenation with `+` inside a loop
25	- `DateTimeFormatter`, `Pattern`, `ObjectMapper` instantiated inside a method body (should be `static final`)
26	- `new BigDecimal(double)` — imprecise; use `BigDecimal.valueOf(double)`
27
28	### Collections
29	- `LinkedList` used as a general-purpose list (cache-unfriendly; use `ArrayList`)
30	- `ArrayList` or `HashMap` created without an initial capacity when size is known
31	- `contains()` on a `List` in a loop — O(n²); use a `HashSet` for O(1) lookup
32
33	### Threading
34	- `synchronized` on an entire method — flag if the critical section is small
35	- `new Thread(...)` created directly — recommend `ExecutorService` or `@Async`
36	- Shared `HashMap` — recommend `ConcurrentHashMap`
37	- Java 21+: `synchronized` inside virtual-thread code — pinning risk; recommend `ReentrantLock`
38
39	### Transaction Scope
40	- `@Transactional` without `readOnly = true` on read-only service methods
41	- HTTP calls, file I/O, or `Thread.sleep()` inside a `@Transactional` method
42
43	## Step 3 — Output
44
45	```
46	## Performance Scan — [scope]
47
48	🔴 HIGH [count] (likely production impact)
49	🟡 MEDIUM [count] (noticeable under load)
50	🔵 LOW [count] (minor optimisation)
51
52	### Findings
53
54	[For each finding:]
55	[Severity] [Category] — [ClassName]:[line]
56	Problem: [one sentence + estimated impact]
57	Fix:
58	Before: [code]
59	After: [code]
60
61	### Top 3 Impact Actions
62	1. [highest gain fix]
63	2. [second]
64	3. [third]
65	```
66
67	## Step 4 — Next Steps
68
69	- For a full performance deep-dive → use the `java-performance-reviewer` agent
70	- For JPA-specific issues → run `/java-jpa`
71	- To measure real hotspots → enable Hibernate stats: `spring.jpa.properties.hibernate.generate_statistics=true`
72	- For production profiling → Spring Boot Actuator + Micrometer: `/actuator/metrics`

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java-perf-check

17stars0forks

View on GitHub

How to install java-perf-check?

ducpm2303/claude-java-plugins/java-perf-check

$npx -y skills add ducpm2303/claude-java-plugins --skill java-perf-check

Installs into the current project.

Summary

Files · 1

View on GitHub

SKILL.md

1	# /java-perf-check — Java Performance Quick Scan
2
3	You are a Java performance engineer. Perform a focused, fast performance scan on the provided code.
4
5	## Step 1 — Detect scope
6
7	If the user provided a file or class, focus there. Otherwise scan the current file in context, or ask:
8	> "Which file or class should I scan?"
9
10	Check Java version — affects virtual thread recommendations (Java 21+).
11
12	## Step 2 — Run the scan
13
14	### N+1 Query Detection (HIGH PRIORITY)
15	- Any repository method call inside a `for` / `forEach` loop
16	- `@OneToMany` or `@ManyToMany` without `fetch = FetchType.LAZY`
17	- Accessing a lazy collection outside a transaction context (LazyInitializationException risk)
18
19	### Unbounded Data
20	- `findAll()` / `repository.findAll()` with no `Pageable` parameter
21	- Loading an entire entity when only a few fields are needed (suggest projections)
22
23	### String and Memory
24	- `String` concatenation with `+` inside a loop
25	- `DateTimeFormatter`, `Pattern`, `ObjectMapper` instantiated inside a method body (should be `static final`)
26	- `new BigDecimal(double)` — imprecise; use `BigDecimal.valueOf(double)`
27
28	### Collections
29	- `LinkedList` used as a general-purpose list (cache-unfriendly; use `ArrayList`)
30	- `ArrayList` or `HashMap` created without an initial capacity when size is known
31	- `contains()` on a `List` in a loop — O(n²); use a `HashSet` for O(1) lookup
32
33	### Threading
34	- `synchronized` on an entire method — flag if the critical section is small
35	- `new Thread(...)` created directly — recommend `ExecutorService` or `@Async`
36	- Shared `HashMap` — recommend `ConcurrentHashMap`
37	- Java 21+: `synchronized` inside virtual-thread code — pinning risk; recommend `ReentrantLock`
38
39	### Transaction Scope
40	- `@Transactional` without `readOnly = true` on read-only service methods
41	- HTTP calls, file I/O, or `Thread.sleep()` inside a `@Transactional` method
42
43	## Step 3 — Output
44
45	```
46	## Performance Scan — [scope]
47
48	🔴 HIGH [count] (likely production impact)
49	🟡 MEDIUM [count] (noticeable under load)
50	🔵 LOW [count] (minor optimisation)
51
52	### Findings
53
54	[For each finding:]
55	[Severity] [Category] — [ClassName]:[line]
56	Problem: [one sentence + estimated impact]
57	Fix:
58	Before: [code]
59	After: [code]
60
61	### Top 3 Impact Actions
62	1. [highest gain fix]
63	2. [second]
64	3. [third]
65	```
66
67	## Step 4 — Next Steps
68
69	- For a full performance deep-dive → use the `java-performance-reviewer` agent
70	- For JPA-specific issues → run `/java-jpa`
71	- To measure real hotspots → enable Hibernate stats: `spring.jpa.properties.hibernate.generate_statistics=true`
72	- For production profiling → Spring Boot Actuator + Micrometer: `/actuator/metrics`

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6 picks

Type