Tuesday, November 30, 2010

Iterate through values of Java Hashtable example

This example shows how to iterate over hash table using enumerator:

//create Hashtable object    
Hashtable ht = new Hashtable();
//add key value pairs to Hashtable
//get Enumeration of values contained in Hashtable using
//Enumeration elements() method of Hashtable class
Enumeration e = ht.elements();
//iterate through Hashtable values Enumeration

Monday, November 29, 2010

How do I convert String to Date object?

The following code shows how we can convert a string representation of date into java.util.Date object.
To convert a string of date we can use the help from java.text.SimpleDateFormat that extends java.text.DateFormat abstract class.

import java.text.DateFormat;
import java.text.SimpleDateFormat;
import java.text.ParseException;
import java.util.Date;

public Date StringToDate
         DateFormat df = new SimpleDateFormat("dd/MM/yyyy");

            Date today = df.parse("20/12/2005");           
           System.out.println("Today = " + df.format(today));
      } catch (ParseException e)
            System.out.println("Cannot convert to date "+e);
And here is the result of our code:
Today = 20/12/2005
The example starts by creating an instance of SimpleDateFormat with "dd/MM/yyyy" format which mean that the date string is formatted in day-month-year sequence.
Finally using the parse(String source) method we can get the Date instance. Because parse method can throw java.text.ParseException exception if the supplied date is not in a valid format; we need to catch it.
Here are the list of defined patterns that can be used to format the date taken from the Java class documentation.
Letter Date / Time Component Examples
G Era designator AD
y Year 1996; 96
M Month in year July; Jul; 07
w Week in year 27
W Week in month 2
D Day in year 189
d Day in month 10
F Day of week in month 2
E Day in week Tuesday; Tue
a Am/pm marker PM
H Hour in day (0-23) 0
k Hour in day (1-24) 24
K Hour in am/pm (0-11) 0
h Hour in am/pm (1-12) 12
m Minute in hour 30
s Second in minute 55
S Millisecond 978
z Time zone Pacific Standard Time; PST; GMT-08:00
Z Time zone -0800

Tuesday, November 23, 2010

Creating a delimiter separated list from list of strings

When you have a list of strings like IList<string> of IEnumerable<string> and you want to convert it to for example a comma separated list you can easily do that with the String.Join method.
List<string> list = new List<string>() { "A" , "B", "C", "D", "E" };
string commaSeparated = String.Join(",", list.ToArray());
The output will be like this:
This is an easy and clean way to create a delimiter separeated list of strings.