黑马程序员 Java 常用类

 1 class MathDemo
 2 {
 3     public static void main(String[] args)
 4     {
 5         double d =Math.ceil(-16.12);//返回大于指定数据的最小整数
 6         double d2 =Math.floor(-12.34);//返回小于指定数据的最大整数
 7         double d3 =Math.round(12.34);//四舍五入
 8         double d4 =Math.pow(2,3);//2的3次方
 9         sop("d="+d);
10         sop("d2="+d2);
11         sop("d3="+d3);
12         sop("d4="+d4);
13 
14 
15     }
16     public static void sop(Object obj)
17     {
18         System.out.println(obj);
19     }
20 
21 }

random方法

 1 import java.util.*;
 2 class MathDemo2 
 3 {
 4     public static void main(String[] args) 
 5     {
 6         //生成0到10之间的随机数
 7         for (int x=0;x<10 ;x++ )
 8         {        
 9             int i =(int)(Math.random()*10+1);
10             System.out.println(i);
11         }
12         System.out.println("--------------");
13         Random r =new Random();
14         for (int x=0;x<10 ;x++ )
15         {
16             int i= r.nextInt(10);
17             System.out.println(i);
18 
19         }
20         
21 
22

 1 import java.util.*;
 2 import java.text.*;
 3 class DateDemo 
 4 {
 5     public static void main(String[] args) 
 6     {
 7         Date d =new Date();
 8         System.out.println(d);
 9         SimpleDateFormat sdf =new SimpleDateFormat("yyyy年MM月dd日 E hh:mm:ss");
10         String time =sdf.format(d);
11         System.out.println("time="+time);
12     }
13 }

 1 import java.util.*;
 2 class CalendarDemo 
 3 {
 4     public static void main(String[] args) 
 5     {
 6         Calendar c =Calendar.getInstance();
 7 
 8         c.set(2012,11,02);
 9 
10         printCalendar(c);
11     }
12     public static void printCalendar(Calendar c)
13     {
14         String[] months={"一月","二月","三月","四月",
15             "五月","六月","七月","八月",
16             "九月","十月","十一月","十二月"};
17         String[] weeks={"","星期日","星期一","星期二","星期三","星期四"
18         ,"星期五","星期六"};
19         int index =c.get(Calendar.MONTH);
20         int index1 =c.get(Calendar.DAY_OF_WEEK);
21         System.out.println(c.get(Calendar.YEAR)+"年");
22         System.out.println(months[index]);
23         System.out.println(weeks[index1]);
24     }
25 }

posted on 2012-06-12 16:22 Lincon Ma 阅读(118) 评论(0) 编辑收藏举报