Good web site for java examples

See http://javacodex.com

Get Operating System info using java

Source:

import java.lang.management.*;

public class OperatingSystem {
   public static void main(String[] args) {
      OperatingSystemMXBean os = ManagementFactory.getOperatingSystemMXBean();
      System.out.println("System Architecture: " + os.getArch());
      System.out.println("Operating System: " + os.getName());
      System.out.println("Version: " + os.getVersion());
   }
}

Output:

   # java OperatingSystem
   System Architecture: sparc
   Operating System: SunOS
   Version: 5.11

Java memory usage example

Source:

import java.lang.management.ManagementFactory;
import java.lang.management.MemoryMXBean;
import java.lang.management.MemoryUsage;

public class MemoryUsed {
   public static void main(String[] args) {
      MemoryMXBean m = ManagementFactory.getMemoryMXBean();
      System.out.println(m.getHeapMemoryUsage());
   }
}

Output:

   # java MemoryUsed
   init = 16777216(16384K) used = 287832(281K) 
   committed = 16252928(15872K) max = 518979584(506816K)

Print content of a text file

Source:

import java.io.*;
class PrintFile {
   public static void main (String[] args) {
      File source = new File ("MyFile.txt");
      FileReader fr = null;
      try {
         fr = new FileReader (source);
         int x;
         while ( (x = fr.read()) != -1 ) {
            System.out.printf ("%c", x);
         }
      } catch (Exception e) {
      } 
   }
}

Output:

   # java PrintFile
   This is line one.
   This is line two.
   This is line three.
   This is line four.

Current Time

Source:

import java.util.*;

public class CurrentTime{
   public static void main(String[] args){
      Calendar calendar = new GregorianCalendar();
      int h = calendar.get(Calendar.HOUR);
      int m = calendar.get(Calendar.MINUTE);
      int s = calendar.get(Calendar.SECOND);
      System.out.println("Time : " + h + ":" + m + ":" + s );
   }
}

Output:

   # java CurrentTime
   Current Time : 10:25:45

SimpleDateFormat

Source:

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

public class Example {
   public static void main(String[] args) {
      Date d = new Date();
      SimpleDateFormat sdf = new SimpleDateFormat("MM-dd-yyyy");
      System.out.println("Date: " + sdf.format(d));
   }
}

Output:

   # java Example
   Date: 01-06-2013   

Simple Try Catch

Source:

public class TryCatch {
   public static void main(String[] args) {
      try {
         int x = 1 / 0;
      } catch (Exception e) {
         System.out.println("Exception caught: " + e);
      }
   }
} 

Output:

   # java TryCatch
   Exception caught: java.lang.ArithmeticException: / by zero