public class Singleton { private static Singleton instance; private Singleton() {} public static Singleton getInstance() { if (instance == null) { instance = new Singleton(); } return instance; }
}
1.2 工厂模式
工厂模式用于创建对象,而不暴露对象的创建逻辑。以下是一个工厂模式的示例代码:
public interface Product { void use();
}
public class ConcreteProduct implements Product { @Override public void use() { System.out.println("Using concrete product"); }
}
public class Factory { public static Product createProduct() { return new ConcreteProduct(); }
}
import static org.junit.Assert.assertEquals;
import org.junit.Test;
public class UserTest { @Test public void testAge() { User user = new User("Alice", 25); assertEquals(25, user.getAge()); }
}