class Count { public static int counter; static {//只运行一次 counter = 123; System.out.println("Now in static block."); } public void test(){ System.out.println("test method=="+counter); } } public class Test { public static void main(String args[]) { System.out.println("counter=" + Count.counter); new Count().test(); } } 运行结果是: Now in static block. counter=123 test method==123 5:静态 import 当我们要获取一个随机数时,写法是: public class Test { public static void main(String[] args) { double randomNum = Math.random(); System.out.println("the randomNum=="+randomNum); } }//源代码片段来自云代码http://yuncode.net