1、静态实例初始化只进行一次
2、静态实例初始化只有在必要时刻进行（如果1和2都注释掉，静态实例初始化不会进行）
例：
//: ExplicitStatic.java // Explicit static initialization // with the "static" clause. class Cup { Cup(int marker) { System.out.println("Cup(" + marker + ")"); } void f(int marker) { System.out.println("f(" + marker + ")"); } } class Cups { static Cup c1; static Cup c2; static { c1 = new Cup(1); c2 = new Cup(2); } Cups() { System.out.println("Cups()"); } } public class ExplicitStatic { public static void main(String[] args) { System.out.println("Inside main()"); Cups.c1.f(99); // (1) } static Cups x = new Cups(); // (2) static Cups y = new Cups(); // (2) } ///:~
