How to get RAM size using java?

package com.demo.memoryheap;

import java.lang.management.ManagementFactory;

/**
 * @author abdul
 *
 */
public class FreeMemoryUsingMxBean {

    /**
     * @param args
     */
    public static void main(String[] args) {
        com.sun.management.OperatingSystemMXBean mxbean = (com.sun.management.OperatingSystemMXBean) ManagementFactory.getOperatingSystemMXBean();
       
        System.out.println("Total Memory in MB: " + mxbean.getTotalPhysicalMemorySize()/(1024*1024));
       
        System.out.println("Free Memory in MB: " + mxbean.getFreePhysicalMemorySize()/(1024*1024));
    }
}

Note : If you get access restriction error while working on Eclipse , check this :
Access Restriction issue

Access restriction on class due to restriction on required library rt.jar for OperatingSystemMXBean ?

Its work for me :

1. Go to the Build Path settings in the project properties.
2. Remove the JRE System Library
3. Add it back; Select "Add Library" and select the JRE System Library. The default worked for me

How to convert InputStream to String in Java?

/**
 *
 */
package convert.stream.to.string;

import java.io.BufferedReader;
import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;

/**
 * @author abdul
 *
 */
public class StreamToString {

    /**
     * @param args
     */
    public static void main(String[] args) {
        StreamToString streamToString = new StreamToString();
     
        //intilize an InputStream
        InputStream is = new ByteArrayInputStream("file content:\nData1\nData2".getBytes());
     
        /*
         * Call the method to convert the stream to string
         */
        System.out.println(streamToString.convertStreamToString(is));
    }

    private String convertStreamToString(InputStream is) {
        /*
         * To convert the InputStream to String we use the BufferedReader.readLine()
         * method. We iterate until the BufferedReader return null which means
         * there's no more data to read. Each line will appended to a StringBuilder
         * and returned as String.
         */
        BufferedReader reader = new BufferedReader(new InputStreamReader(is));
        StringBuilder sb = new StringBuilder();

        String line = null;
        try {
            while ((line = reader.readLine()) != null) {
                sb.append(line + "\n");
            }
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            try {
                is.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        return sb.toString();
    }
}



Output:
file content:
Data1
Data2

How to find exact version of Red Hat Linux

[root@localhost ]# cat /etc/redhat-release
Red Hat Enterprise Linux Server release 5.2 (Tikanga)


For others:

Slackware: /etc/slackware-version
Mandrake: /etc/mandrake-release
Red Hat: /etc/redhat-release
Fedora: /etc/fedora-release

How to configure session timeout for putty

Click on the upper left hand corner of your putty screen, then click on 'Change Settings', then 'Connection'. I have my 'keepalive' set to 300.
Now It will time out after 5 minutes.

How to create a ant log file

ant -logfile <filename>.log

Get Sub List of Java ArrayList Example

package com.subList.demo;

import java.util.ArrayList;
import java.util.List;

/**
 * This Java Example shows how to get sub list of java ArrayList using subList method.
 *
 * @author abdul
 */
public class SubListDemo {

    public static void main(String args[]) {

        //create an ArrayList object
        List<String> list = new ArrayList<String>();
        int range = 4;

        //Add elements to Arraylist
        list.add("A");
        list.add("B");
        list.add("C");
        list.add("D");
        list.add("E");
        list.add("F");
        list.add("G");
        list.add("H");
        list.add("I");
        list.add("J");
        list.add("K");
        list.add("L");
        list.add("M");
        list.add("N");
        list.add("O");
        display("Displaying all elements of the list : ", list);

        if(list.size() > range) {
            int from = 0;
            int to = range;
            List<String> lt = null;
            do {
                //Check whether "to" value never exceeds from the list size
                //otherwise it would throw error while fetching subList
                if(list.size() - from > range ) {

                    // To get a sub list of Java ArrayList use List subList(int startIndex, int endIndex) method.
                    //This method returns an object of type List containing elements from startIndex to endIndex - 1
                    lt = list.subList(from, to);

                    display("SubList from " + from + " to " + to, lt);
                } else {
                    lt = list.subList(from, list.size());
                    display("SubList from " + from + " to " + list.size(),lt);
                }
                from += range;
                to += range;
            }while(from < list.size());
        } else {
            display("Displaying all elements of the list : " , list);
        }
    }

    /**
     * Display elements of sub list.
     * @param message
     * @param list sublist of the list to print
     */
    private static void display(String message,List<String> list) {
        System.out.println(message + "\nList: " + list);
    }
}

Output:
Displaying all elements of the list :
List: [A, B, C, D, E, F, G, H, I, J, K, L, M, N, O]
SubList from 0 to 4
List: [A, B, C, D]
SubList from 4 to 8
List: [E, F, G, H]
SubList from 8 to 12
List: [I, J, K, L]
SubList from 12 to 15
List: [M, N, O]


Related link:
http://docs.oracle.com/javase/1.4.2/docs/api/java/util/List.html