solid-principles

Name: solid-principles
Author: decebals

686stars133forks

How to install solid-principles?

decebals/claude-code-java/solid-principles

$npx -y skills add decebals/claude-code-java --skill solid-principles

Installs into the current project.

Summary

SOLID principles checklist with Java examples. Use when reviewing classes, refactoring code, or when user asks about Single Responsibility, Open/Closed, Liskov, Interface Segregation, or Dependency Inversion.

Files · 1

View on GitHub

SKILL.md

1	# SOLID Principles Skill
2
3	Review and apply SOLID principles in Java code.
4
5	## When to Use
6	- User says "check SOLID" / "SOLID review" / "is this class doing too much?"
7	- Reviewing class design
8	- Refactoring large classes
9	- Code review focusing on design
10
11	---
12
13	## Quick Reference
14
15	\| Letter \| Principle \| One-liner \|
16	\|--------\|-----------\|-----------\|
17	\| S \| Single Responsibility \| One class = one reason to change \|
18	\| O \| Open/Closed \| Open for extension, closed for modification \|
19	\| L \| Liskov Substitution \| Subtypes must be substitutable for base types \|
20	\| I \| Interface Segregation \| Many specific interfaces > one general interface \|
21	\| D \| Dependency Inversion \| Depend on abstractions, not concretions \|
22
23	---
24
25	## S - Single Responsibility Principle (SRP)
26
27	> "A class should have only one reason to change."
28
29	### Violation
30
31	```java
32	// ❌ BAD: UserService does too much
33	public class UserService {
34
35	public User createUser(String name, String email) {
36	// validation logic
37	if (email == null \|\| !email.contains("@")) {
38	throw new IllegalArgumentException("Invalid email");
39	}
40
41	// persistence logic
42	User user = new User(name, email);
43	entityManager.persist(user);
44
45	// notification logic
46	String subject = "Welcome!";
47	String body = "Hello " + name;
48	emailClient.send(email, subject, body);
49
50	// audit logic
51	auditLog.log("User created: " + email);
52
53	return user;
54	}
55	}
56	```
57
58	Problems:
59	- Validation changes? Modify UserService
60	- Email template changes? Modify UserService
61	- Audit format changes? Modify UserService
62	- Hard to test each concern separately
63
64	### Refactored
65
66	```java
67	// ✅ GOOD: Each class has one responsibility
68
69	public class UserValidator {
70	public void validate(String name, String email) {
71	if (email == null \|\| !email.contains("@")) {
72	throw new ValidationException("Invalid email");
73	}
74	}
75	}
76
77	public class UserRepository {
78	public User save(User user) {
79	entityManager.persist(user);
80	return user;
81	}
82	}
83
84	public class WelcomeEmailSender {
85	public void sendWelcome(User user) {
86	String subject = "Welcome!";
87	String body = "Hello " + user.getName();
88	emailClient.send(user.getEmail(), subject, body);
89	}
90	}
91
92	public class UserAuditLogger {
93	public void logCreation(User user) {
94	auditLog.log("User created: " + user.getEmail());
95	}
96	}
97
98	public class UserService {
99	private final UserValidator validator;
100	private final UserRepository repository;
101	private final WelcomeEmailSender emailSender;
102	private final UserAuditLogger auditLogger;
103
104	public User createUser(String name, String email) {
105	validator.validate(name, email);
106	User user = repository.save(new User(name, email));
107	emailSender.sendWelcome(user);
108	auditLogger.logCreation(user);
109	return user;
110	}
111	}
112	```
113
114	### How to Detect SRP Violations
115
116	- Class has many `import` statements from different domains
117	- Class name contains "And" or "Manager" or "Handler" (often)
118	- Methods operate on unrelated data
119	- Changes in one area require touching unrelated methods
120	- Hard to name the class concisely
121
122	### Quick Check Questions
123
124	1. Can you describe the class purpose in one sentence without "and"?
125	2. Would different stakeholders request changes to this class?
126	3. Are there methods that don't use most of the class fields?
127
128	---
129
130	## O - Open/Closed Principle (OCP)
131
132	> "Software entities should be open for extension, but closed for modification."
133
134	### Violation
135
136	```java
137	// ❌ BAD: Must modify class to add new discount type
138	public class DiscountCalculator {
139
140	public double calculate(Order order, String discountType) {
141	if (discountType.equals("PERCENTAGE")) {
142	return order.getTotal() * 0.1;
143	} else if (discountType.equals("FIXED")) {
144	return 50.0;
145	} else if (discountType.equals("LOYALTY")) {
146	return order.getTotal() * order.getCustomer().getLoyaltyRate();
147	}
148	// Every new discount type = modify this class
149	return 0;
150	}
151	}
152	```
153
154	### Refactored
155
156	```java
157	// ✅ GOOD: Add new discounts without modifying existing code
158
159	public interface DiscountStrategy {
160	double calculate(Order order);
161	boolean supports(String discountType);
162	}
163
164	public class PercentageDiscount implements DiscountStrategy {
165	@Override
166	public double calculate(Order order) {
167	return order.getTotal() * 0.1;
168	}
169
170	@Override
171	public boolean supports(String discountType) {
172	return "PERCENTAGE".equals(discountType);
173	}
174	}
175
176	public class FixedDiscount implements DiscountStrategy {
177	@Override
178	public double calculate(Order

People who liked this also viewed

6 picks

Type

solid-principles

686stars133forks

View on GitHub

How to install solid-principles?

decebals/claude-code-java/solid-principles

$npx -y skills add decebals/claude-code-java --skill solid-principles

Installs into the current project.

Summary

Files · 1

View on GitHub

SKILL.md

1	# SOLID Principles Skill
2
3	Review and apply SOLID principles in Java code.
4
5	## When to Use
6	- User says "check SOLID" / "SOLID review" / "is this class doing too much?"
7	- Reviewing class design
8	- Refactoring large classes
9	- Code review focusing on design
10
11	---
12
13	## Quick Reference
14
15	\| Letter \| Principle \| One-liner \|
16	\|--------\|-----------\|-----------\|
17	\| S \| Single Responsibility \| One class = one reason to change \|
18	\| O \| Open/Closed \| Open for extension, closed for modification \|
19	\| L \| Liskov Substitution \| Subtypes must be substitutable for base types \|
20	\| I \| Interface Segregation \| Many specific interfaces > one general interface \|
21	\| D \| Dependency Inversion \| Depend on abstractions, not concretions \|
22
23	---
24
25	## S - Single Responsibility Principle (SRP)
26
27	> "A class should have only one reason to change."
28
29	### Violation
30
31	```java
32	// ❌ BAD: UserService does too much
33	public class UserService {
34
35	public User createUser(String name, String email) {
36	// validation logic
37	if (email == null \|\| !email.contains("@")) {
38	throw new IllegalArgumentException("Invalid email");
39	}
40
41	// persistence logic
42	User user = new User(name, email);
43	entityManager.persist(user);
44
45	// notification logic
46	String subject = "Welcome!";
47	String body = "Hello " + name;
48	emailClient.send(email, subject, body);
49
50	// audit logic
51	auditLog.log("User created: " + email);
52
53	return user;
54	}
55	}
56	```
57
58	Problems:
59	- Validation changes? Modify UserService
60	- Email template changes? Modify UserService
61	- Audit format changes? Modify UserService
62	- Hard to test each concern separately
63
64	### Refactored
65
66	```java
67	// ✅ GOOD: Each class has one responsibility
68
69	public class UserValidator {
70	public void validate(String name, String email) {
71	if (email == null \|\| !email.contains("@")) {
72	throw new ValidationException("Invalid email");
73	}
74	}
75	}
76
77	public class UserRepository {
78	public User save(User user) {
79	entityManager.persist(user);
80	return user;
81	}
82	}
83
84	public class WelcomeEmailSender {
85	public void sendWelcome(User user) {
86	String subject = "Welcome!";
87	String body = "Hello " + user.getName();
88	emailClient.send(user.getEmail(), subject, body);
89	}
90	}
91
92	public class UserAuditLogger {
93	public void logCreation(User user) {
94	auditLog.log("User created: " + user.getEmail());
95	}
96	}
97
98	public class UserService {
99	private final UserValidator validator;
100	private final UserRepository repository;
101	private final WelcomeEmailSender emailSender;
102	private final UserAuditLogger auditLogger;
103
104	public User createUser(String name, String email) {
105	validator.validate(name, email);
106	User user = repository.save(new User(name, email));
107	emailSender.sendWelcome(user);
108	auditLogger.logCreation(user);
109	return user;
110	}
111	}
112	```
113
114	### How to Detect SRP Violations
115
116	- Class has many `import` statements from different domains
117	- Class name contains "And" or "Manager" or "Handler" (often)
118	- Methods operate on unrelated data
119	- Changes in one area require touching unrelated methods
120	- Hard to name the class concisely
121
122	### Quick Check Questions
123
124	1. Can you describe the class purpose in one sentence without "and"?
125	2. Would different stakeholders request changes to this class?
126	3. Are there methods that don't use most of the class fields?
127
128	---
129
130	## O - Open/Closed Principle (OCP)
131
132	> "Software entities should be open for extension, but closed for modification."
133
134	### Violation
135
136	```java
137	// ❌ BAD: Must modify class to add new discount type
138	public class DiscountCalculator {
139
140	public double calculate(Order order, String discountType) {
141	if (discountType.equals("PERCENTAGE")) {
142	return order.getTotal() * 0.1;
143	} else if (discountType.equals("FIXED")) {
144	return 50.0;
145	} else if (discountType.equals("LOYALTY")) {
146	return order.getTotal() * order.getCustomer().getLoyaltyRate();
147	}
148	// Every new discount type = modify this class
149	return 0;
150	}
151	}
152	```
153
154	### Refactored
155
156	```java
157	// ✅ GOOD: Add new discounts without modifying existing code
158
159	public interface DiscountStrategy {
160	double calculate(Order order);
161	boolean supports(String discountType);
162	}
163
164	public class PercentageDiscount implements DiscountStrategy {
165	@Override
166	public double calculate(Order order) {
167	return order.getTotal() * 0.1;
168	}
169
170	@Override
171	public boolean supports(String discountType) {
172	return "PERCENTAGE".equals(discountType);
173	}
174	}
175
176	public class FixedDiscount implements DiscountStrategy {
177	@Override
178	public double calculate(Order

People who liked this also viewed

6 picks

Type