Static Classes - Week 5 Visual

A static class is a library of related functions, not a thing you create with new. Java's Math class is the canonical example.

java.lang.Math

Static class — no instances allowed

public static final double PI = 3.14159265...;

public static final double E = 2.71828182...;

public static double sqrt(double a) // → double

public static double pow(double a, double b) // → double

public static double floor(double a) // → double

public static double ceil(double a) // → double

public static long round(double a) // → long

public static double abs(double a) // → double

public static double max(double a, double b) // → double

public static double min(double a, double b) // → double

✕ Cannot do this

Math m = new Math();
The constructor is private, so the compiler won't let you.

Live Examples

Math.PI 3.141592653589793

Math.sqrt(25) 5.0

Math.pow(5, 2) 25.0

Math.floor(12.8) 12.0

Math.ceil(12.2) 13.0

Math.round(12.5) 13

Math.abs(-7.3) 7.3

Math.max(10, 25) 25.0

Try it: Area of a circle = Math.PI * Math.pow(r, 2)

radius = → area =

When to make a static class: when you have a group of helper functions that don't need any per-instance data — just inputs and outputs. A name formatter. A unit converter. A pricing rule library. The recipe is always the same: every member is static, the constructor is private (so nobody can new it), and consumers call ClassName.method() directly.

Static Classes — the Math pattern