Variables, Scope & var

An instance variable is a per-object, non-static field that gets a default value automatically and lives as long as the object exists on the heap.

It does not compile. Local variables get no default value, and Java's definite-assignment rule rejects any read of a local that has not been assigned on every possible path.

var lets the compiler infer a local variable's type from its initializer at compile time. It is shorthand for the full type, not dynamic typing.