package text;import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Random;//  Java随机
public class Demo {public static void first(String[] args) {Random rand = new Random();for (int i = 0; i < 5; i++) {//System.out.println(Math.random());//随机小数System.out.println(rand.nextInt(10));//随机0-9的整数System.out.println(rand.nextInt(10) + 1);//随机1-10的整数System.out.println(rand.nextInt(11) + 10);//随机10-20的整数System.out.println(rand.nextBoolean());//随机真假System.out.println(rand.nextDouble());//随机小数
        }}
//    随机日期public static void date(String[] args) {Random rand = new Random();Calendar c = Calendar.getInstance();SimpleDateFormat sdf = new SimpleDateFormat("yyy-MM-dd HH:mm:ss");long start = c.getTime().getTime();System.out.println(sdf.format(c.getTime()));c.set(2000,1,1,0,0,0);long end = c.getTime().getTime();System.out.println(sdf.format(c.getTime()));// long time = Math.round(rand.nextDouble() * (end - start) + start);// c.setTimeInMillis(time);
        System.out.println(sdf.format(c.getTime()));}
//  随机取出一个字母public static void world(String[] args) {//string stringBuffer stringBuilder的区别StringBuffer str = new StringBuffer("ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz1234567890");StringBuffer temp = new StringBuffer("");Random rand = new Random();for (int i = 0; i < 10; i++) {temp.append(str.charAt(rand.nextInt(str.length())));}System.out.println(temp.toString());}
// 随机取出三个姓名且不重复public static void main(String[] args) {String[] arr = new String[]{"李飞","王伟","关羽","刘备","张飞"};Random rand = new Random();StringBuffer temp = new StringBuffer("");int i = 3;while(i > 0) {String name =arr[rand.nextInt(arr.length)];if(temp.indexOf(name) == -1){temp.append(name+" ");i--;}}System.out.println(temp.toString());}
}