design-patterns

Name: design-patterns
Author: decebals

686stars133forks

How to install design-patterns?

decebals/claude-code-java/design-patterns

$npx -y skills add decebals/claude-code-java --skill design-patterns

Installs into the current project.

Summary

Common design patterns with Java examples (Factory, Builder, Strategy, Observer, Decorator, etc.). Use when user asks "implement pattern", "use factory", "strategy pattern", or when designing extensible components.

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SKILL.md

1	# Design Patterns Skill
2
3	Practical design patterns reference for Java with modern examples.
4
5	## When to Use
6	- User asks to implement a specific pattern
7	- Designing extensible/flexible components
8	- Refactoring rigid code structures
9	- Code review suggests pattern usage
10
11	---
12
13	## Quick Reference: When to Use What
14
15	\| Problem \| Pattern \|
16	\|---------\|---------\|
17	\| Complex object construction \| Builder \|
18	\| Create objects without specifying class \| Factory \|
19	\| Multiple algorithms, swap at runtime \| Strategy \|
20	\| Add behavior without changing class \| Decorator \|
21	\| Notify multiple objects of changes \| Observer \|
22	\| Ensure single instance \| Singleton \|
23	\| Convert incompatible interfaces \| Adapter \|
24	\| Define algorithm skeleton \| Template Method \|
25
26	---
27
28	## Creational Patterns
29
30	### Builder
31
32	Use when: Object has many parameters, some optional.
33
34	```java
35	// ❌ Telescoping constructor antipattern
36	public class User {
37	public User(String name) { }
38	public User(String name, String email) { }
39	public User(String name, String email, int age) { }
40	public User(String name, String email, int age, String phone) { }
41	// ... explosion of constructors
42	}
43
44	// ✅ Builder pattern
45	public class User {
46	private final String name; // required
47	private final String email; // required
48	private final int age; // optional
49	private final String phone; // optional
50	private final String address; // optional
51
52	private User(Builder builder) {
53	this.name = builder.name;
54	this.email = builder.email;
55	this.age = builder.age;
56	this.phone = builder.phone;
57	this.address = builder.address;
58	}
59
60	public static Builder builder(String name, String email) {
61	return new Builder(name, email);
62	}
63
64	public static class Builder {
65	// Required
66	private final String name;
67	private final String email;
68	// Optional with defaults
69	private int age = 0;
70	private String phone = "";
71	private String address = "";
72
73	private Builder(String name, String email) {
74	this.name = name;
75	this.email = email;
76	}
77
78	public Builder age(int age) {
79	this.age = age;
80	return this;
81	}
82
83	public Builder phone(String phone) {
84	this.phone = phone;
85	return this;
86	}
87
88	public Builder address(String address) {
89	this.address = address;
90	return this;
91	}
92
93	public User build() {
94	return new User(this);
95	}
96	}
97	}
98
99	// Usage
100	User user = User.builder("John", "john@example.com")
101	.age(30)
102	.phone("+1234567890")
103	.build();
104	```
105
106	With Lombok:
107	```java
108	@Builder
109	@Getter
110	public class User {
111	private final String name;
112	private final String email;
113	@Builder.Default private int age = 0;
114	private String phone;
115	}
116	```
117
118	---
119
120	### Factory Method
121
122	Use when: Need to create objects without specifying exact class.
123
124	```java
125	// ✅ Factory Method pattern
126	public interface Notification {
127	void send(String message);
128	}
129
130	public class EmailNotification implements Notification {
131	@Override
132	public void send(String message) {
133	System.out.println("Email: " + message);
134	}
135	}
136
137	public class SmsNotification implements Notification {
138	@Override
139	public void send(String message) {
140	System.out.println("SMS: " + message);
141	}
142	}
143
144	public class PushNotification implements Notification {
145	@Override
146	public void send(String message) {
147	System.out.println("Push: " + message);
148	}
149	}
150
151	// Factory
152	public class NotificationFactory {
153
154	public static Notification create(String type) {
155	return switch (type.toUpperCase()) {
156	case "EMAIL" -> new EmailNotification();
157	case "SMS" -> new SmsNotification();
158	case "PUSH" -> new PushNotification();
159	default -> throw new IllegalArgumentException("Unknown type: " + type);
160	};
161	}
162	}
163
164	// Usage
165	Notification notification = NotificationFactory.create("EMAIL");
166	notification.send("Hello!");
167	```
168
169	With Spring (preferred):
170	```java
171	public interface NotificationSender {
172	void send(String message);
173	String getType();
174	}
175
176	@Component
177	public class EmailSender implements NotificationSender {
178	@Override public void send(String message) { /* ... */ }
179	@Override public String getType() { return "EMAIL"; }
180	}
181
182	@Component
183	public class SmsSender implements NotificationSender {
184	@Override public void send(String message) { /* ... */ }
185	@Override public String getType() { return "SMS"; }
186	}
187
188	@Component
189	public class NotificationFactory {
190	private final Map<String, NotificationSender> sende

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Type

design-patterns

686stars133forks

View on GitHub

How to install design-patterns?

decebals/claude-code-java/design-patterns

$npx -y skills add decebals/claude-code-java --skill design-patterns

Installs into the current project.

Summary

Files · 1

View on GitHub

SKILL.md

1	# Design Patterns Skill
2
3	Practical design patterns reference for Java with modern examples.
4
5	## When to Use
6	- User asks to implement a specific pattern
7	- Designing extensible/flexible components
8	- Refactoring rigid code structures
9	- Code review suggests pattern usage
10
11	---
12
13	## Quick Reference: When to Use What
14
15	\| Problem \| Pattern \|
16	\|---------\|---------\|
17	\| Complex object construction \| Builder \|
18	\| Create objects without specifying class \| Factory \|
19	\| Multiple algorithms, swap at runtime \| Strategy \|
20	\| Add behavior without changing class \| Decorator \|
21	\| Notify multiple objects of changes \| Observer \|
22	\| Ensure single instance \| Singleton \|
23	\| Convert incompatible interfaces \| Adapter \|
24	\| Define algorithm skeleton \| Template Method \|
25
26	---
27
28	## Creational Patterns
29
30	### Builder
31
32	Use when: Object has many parameters, some optional.
33
34	```java
35	// ❌ Telescoping constructor antipattern
36	public class User {
37	public User(String name) { }
38	public User(String name, String email) { }
39	public User(String name, String email, int age) { }
40	public User(String name, String email, int age, String phone) { }
41	// ... explosion of constructors
42	}
43
44	// ✅ Builder pattern
45	public class User {
46	private final String name; // required
47	private final String email; // required
48	private final int age; // optional
49	private final String phone; // optional
50	private final String address; // optional
51
52	private User(Builder builder) {
53	this.name = builder.name;
54	this.email = builder.email;
55	this.age = builder.age;
56	this.phone = builder.phone;
57	this.address = builder.address;
58	}
59
60	public static Builder builder(String name, String email) {
61	return new Builder(name, email);
62	}
63
64	public static class Builder {
65	// Required
66	private final String name;
67	private final String email;
68	// Optional with defaults
69	private int age = 0;
70	private String phone = "";
71	private String address = "";
72
73	private Builder(String name, String email) {
74	this.name = name;
75	this.email = email;
76	}
77
78	public Builder age(int age) {
79	this.age = age;
80	return this;
81	}
82
83	public Builder phone(String phone) {
84	this.phone = phone;
85	return this;
86	}
87
88	public Builder address(String address) {
89	this.address = address;
90	return this;
91	}
92
93	public User build() {
94	return new User(this);
95	}
96	}
97	}
98
99	// Usage
100	User user = User.builder("John", "john@example.com")
101	.age(30)
102	.phone("+1234567890")
103	.build();
104	```
105
106	With Lombok:
107	```java
108	@Builder
109	@Getter
110	public class User {
111	private final String name;
112	private final String email;
113	@Builder.Default private int age = 0;
114	private String phone;
115	}
116	```
117
118	---
119
120	### Factory Method
121
122	Use when: Need to create objects without specifying exact class.
123
124	```java
125	// ✅ Factory Method pattern
126	public interface Notification {
127	void send(String message);
128	}
129
130	public class EmailNotification implements Notification {
131	@Override
132	public void send(String message) {
133	System.out.println("Email: " + message);
134	}
135	}
136
137	public class SmsNotification implements Notification {
138	@Override
139	public void send(String message) {
140	System.out.println("SMS: " + message);
141	}
142	}
143
144	public class PushNotification implements Notification {
145	@Override
146	public void send(String message) {
147	System.out.println("Push: " + message);
148	}
149	}
150
151	// Factory
152	public class NotificationFactory {
153
154	public static Notification create(String type) {
155	return switch (type.toUpperCase()) {
156	case "EMAIL" -> new EmailNotification();
157	case "SMS" -> new SmsNotification();
158	case "PUSH" -> new PushNotification();
159	default -> throw new IllegalArgumentException("Unknown type: " + type);
160	};
161	}
162	}
163
164	// Usage
165	Notification notification = NotificationFactory.create("EMAIL");
166	notification.send("Hello!");
167	```
168
169	With Spring (preferred):
170	```java
171	public interface NotificationSender {
172	void send(String message);
173	String getType();
174	}
175
176	@Component
177	public class EmailSender implements NotificationSender {
178	@Override public void send(String message) { /* ... */ }
179	@Override public String getType() { return "EMAIL"; }
180	}
181
182	@Component
183	public class SmsSender implements NotificationSender {
184	@Override public void send(String message) { /* ... */ }
185	@Override public String getType() { return "SMS"; }
186	}
187
188	@Component
189	public class NotificationFactory {
190	private final Map<String, NotificationSender> sende

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Type