java.util中一些實用的工具類

一、StringTokenizer，例子以下：

class StringToken
{
    static String str = "1:java;"+"2:perl;"+"3:C/C++;"+"4:shell;";
    
    public static void main(String [] args)
    {
      StringTokenizer ST = new StringTokenizer(str,":;");//以:;爲分隔符
      while(ST.hasMoreTokens()){
          String key = ST.nextToken();
          String value = ST.nextToken();
          System.out.println(key+":"+value);
      }
  

Result：
1:java
2:perl
3:C/C++
4:shell

二、Date

class DateDemo
{

    public static void main(String [] args)
    {
      Date date = new Date();
      System.out.println(date);
      long sec = date.getTime();
      System.out.println(sec);
      long sec2 = System.currentTimeMillis();
      System.out.println(sec2);
    
    }
}

Result：
Fri Jul 22 15:25:26 CST 2011
1311319526595
1311319526610

三、Calendar

class CalendarDemo
{

    public static void main(String [] args)
    {
       Calendar ca = Calendar.getInstance();
       String [] months = {"Jan","Feb","Mar","Apr","May","Jun","Jul","Aug","Sep","Oct","Nov","Dec"};
       System.out.println("Date:");
       System.out.print(months[ca.get(Calendar.MONTH)]+"  ");
       System.out.print(ca.get(Calendar.DATE)+"  ");
       System.out.println(ca.get(Calendar.HOUR)+"  ");
    }
}

Date:
Jul  22  3  

4.Random

public class RandomApp{
    public static void main(String args[]){
        //建立了兩個類Random的對象。
        Random ran1=new Random();
        Random ran2=new Random(12345);
         //產生各類類型的隨機數
        System.out.println("The 1st set of random numbers:");
        System.out.println("\t Integer:"+ran1.nextInt());
        System.out.println("\t Long:"+ran1.nextLong());
        System.out.println("\t Float:"+ran1.nextFloat());//0--1.0之間
        System.out.println("\t Double:"+ran1.nextDouble());//0--1.0之間
        System.out.println("\t Gaussian:"+ran1.nextGaussian());
         //產生同種類型的不一樣的隨機數
        System.out.print("The 2nd set of random numbers:");
        for(int i=0;i<5;i++){
                 System.out.print(ran2.nextInt(12345) + " ");//0--12345之間
        }
    }
}

Result：
The 1st set of random numbers:
     Integer:-1953322287
     Long:-3756646598696960104
     Float:0.09489989
     Double:0.9836372044386406
     Gaussian:-0.16552271256858825
The 2nd set of random numbers:8986 9205 7086 4563 310