📘 Lesson · Lesson 47
Singleton Pattern
Singleton Pattern
What is Singleton?
The Singleton pattern ensures a class has only ONE instance in the whole program — used for things like a database connection or config.
Singleton Example
class Database {
private static Database instance;
private Database() {} // private constructor
public static Database getInstance() {
if (instance == null) {
instance = new Database();
}
return instance;
}
}
Database db1 = Database.getInstance();
Database db2 = Database.getInstance();
System.out.println(db1 == db2); // true (same instance)true
Summary
- Singleton = one instance only, via a private constructor + getInstance().
- Used for shared resources like config or DB connections.
Singleton क्या है?
Singleton pattern सुनिश्चित करता है कि class का पूरे program में सिर्फ एक instance हो — database connection या config जैसी चीज़ों के लिए।
Singleton Example
class Database {
private static Database instance;
private Database() {} // private constructor
public static Database getInstance() {
if (instance == null) {
instance = new Database();
}
return instance;
}
}
Database db1 = Database.getInstance();
Database db2 = Database.getInstance();
System.out.println(db1 == db2); // true (same instance)true
सारांश
- Singleton = सिर्फ एक instance, private constructor + getInstance() से।
- Config या DB connections जैसे shared resources के लिए।