### 随机数 Stringbuffer Random ``` package com.xiaohu.dao; import java.util.Random; public class DAO1 { public static void main(String[] args) { StringBuffer sa = new StringBuffer(); Boolean flag = false; sa.append("hello"); sa.append("world!"); sa.append(flag); System.out.println(sa); Random rad = new Random(); int num = rad.nextInt(50); Boolean b = rad.nextBoolean(); System.out.println(num); System.out.println(b); Random rad1 = new Random(20); int r1 = rad1.nextInt(); System.out.println(r1); } } ``` ####综合案例 Canlendar Calendar canlandar = Calendar.getInstance(); ``` package com.xiaohu.dao; import java.text.SimpleDateFormat; import java.util.Date; import java.util.Random; public class DAO3 { public static void main(String[] args) { String oldName = "tt.jpg"; String lastName = oldName.substring(oldName.lastIndexOf('.')); System.out.println(lastName); Date d = new Date(); SimpleDateFormat f = new SimpleDateFormat("yyyyMMddhhmmss"); String time = f.format(d); Random rad = new Random(); int num = rad.nextInt(Integer.MAX_VALUE); StringBuffer s = new StringBuffer(); s.append(time); s.append(num); s.append(lastName); System.out.println(s); } } ``` ### 数学函数 ``` package com.xiaohu.dao; public class DAO4 { public static void main(String[] args) { double x1 = Math.abs(-23);//绝对值 double x2 = Math.ceil(13.267);//向上取整 double x3 = Math.floor(13.267);//向下取整 double x4 = Math.max(11,22);//两数最大值 double x5 = Math.round(11.5); double x6 = Math.round(11.2);//四舍五入 double x7 = Math.random();//随机数 double x8 = Math.sqrt(16);//开方 System.out.println(x8); } } ``` 最后修改：2024 年 10 月 28 日 © 允许规范转载 打赏 赞赏作者 支付宝微信 赞 如果觉得我的文章对你有用，请随意赞赏
