黑马程序员 Java 常用类

绝地灬酷狼 2021-11-17 00:28 210阅读 0赞

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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 }

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转载于:https://www.cnblogs.com/malinkang1989/archive/2012/06/12/2546491.html