What are sealed classes and sealed methods?
8 minbeginnerOOPsealedinheritance
Quick Answer
Sealed classes cannot be inherited (final class). Sealed methods cannot be overridden in derived classes. Use sealed to prevent inheritance when you want to maintain control over the class design, improve performance, or ensure security. Common examples include String class and utility classes.
Detailed Answer
Sealed Classes are classes that cannot be inherited. They prevent other classes from deriving from them.
Sealed Methods are overridden methods that cannot be overridden further in derived classes.
Example:
// Sealed Class Example
public sealed class FinalClass
{
public void Display()
{
Console.WriteLine("This class cannot be inherited");
}
}
// This will cause a compilation error
// public class DerivedClass : FinalClass { } // ERROR!
// Sealed Method Example
public class BaseClass
{
public virtual void Print()
{
Console.WriteLine("Base Print");
}
}
public class MiddleClass : BaseClass
{
public sealed override void Print()
{
Console.WriteLine("Middle Print - This cannot be overridden further");
}
}
public class DerivedClass : MiddleClass
{
// This will cause a compilation error
// public override void Print() { } // ERROR! Cannot override sealed method
}
// Real-world example: String class in .NET is sealed
// public sealed class String { ... }