四舍五入 %.2f String.fromat()
String.format("%.3f", 3.1415926);
System.out.println(result);
随机数
double rdm=Math.random(); //[0,1)的随机数————double
System.out.println(rdm);
Random random = new Random();
random.nextInt(int bound);---->包头不包尾 例:random.nextInt(11)--->[0,10)
实例:做一个四位验证码
Random random = new Random();
StringBuffer sb = new StringBuffer();
for(int i=0;i<4;i++){
sb.append(random.nextInt(10));
}
System.out.println(sb);