Static methods
Learn static methods and how to call them without an instance.
Static methods
A static method is called through the class name and does not need an instance. It cannot touch instance fields; it can only use static fields.
To define one, write static before the return type: public static int Square(int n). To call it, write MathHelper.Square(5). Helper operations, math calculations and conversions are good candidates for static methods.
When to use a static method?
A static method suits operations that don't need instance state. If a method only looks at its parameters and the class's static members, it can be static.
Examples: int.Parse("42"), Math.Max(3, 5), string.IsNullOrEmpty(s). None of these need an object instance. On the other hand, a method that reads an Account object's Balance field must be an instance method.
Exercise Squaring helper
Add a public static int Square(int n) method to MathHelper. Its body returns n * n. In Main, call MathHelper.Square(5) and print the result.
Show example solution
Add `public static int Square(int n) { return n * n; }` to MathHelper. In Main write `Console.WriteLine(MathHelper.Square(5));`.
Example solution:
using System;
class MathHelper
{
public static int Square(int n)
{
return n * n;
}
}
class Program
{
static void Main()
{
Console.WriteLine(MathHelper.Square(5));
}
}Test yourself
-
Fill in the blank: static method declaration
class MathHelper { public ____ { return n * n; } }Show answer
class MathHelper { public static int Square(int n) { return n * n; } } -
Which statement is correct?
- A static method can only access static members.
- A static method can access instance fields.
- A static method can only be called via an instance.
- A static method can be a constructor.
Show answer
A static method can only access static members. — Correct. A static method cannot touch instance members, only static ones.
-
Match: static method calls
- Math.Max(3, 5)
- larger of two numbers
- int.Parse("42")
- parses string to integer
- MathHelper.Square(5)
- computes the square
- string.IsNullOrEmpty(s)
- checks for empty string