static: Class-Level Members

static means "belongs to the class, not to any object". It shows up in three places a beginner touches immediately.

Static methods are callable without an instance: Math.max(3, 9) works because max is static; every utility-style method in this module is static for the same reason. Inside a static method you can call other static methods of the same class directly — but NOT instance members, because there is no instance yet. That is the real rule behind the beginner error "non-static method cannot be referenced from a static context": main is static, so it can only reach static things (or objects it creates).

Static fields are class-wide values:

static final double VAT_RATE = 0.1;      // constant shared by everyone
static int invocationCount = 0;          // mutable class-wide state (careful!)

static final is Java's way to spell a constant: fixed at creation, shared by all, named in SCREAMING_SNAKE_CASE by convention. Mutable static fields are global variables wearing a suit — a handful of honest uses (counters, shared configuration) and a universe of trouble; avoid them in application code.

Static import lets you skip the class name for heavily used utilities:

import static java.lang.Math.max;
...
int m = max(a, b);

Use sparingly — readability first. The decision rule: something is static when it needs no per-object memory — it transforms its inputs, consults constants, and returns. The moment behavior depends on per-object state, it belongs to objects (Module 7).

Next: overloading — one name, several signatures.