Sunday, April 27, 2014

Get number of memory in Java VM

Every Java application has a single instance of class java.lang.Runtime that allows the application to interface with the environment in which the application is running.
  • long freeMemory()
    Returns the amount of free memory in the Java Virtual Machine.
  • long maxMemory()
    Returns the maximum amount of memory that the Java virtual machine will attempt to use.
  • long totalMemory()
    Returns the total amount of memory in the Java virtual machine.
public class testMem {
    
    public static void main(String[] args){
        System.out.println("helloraspberrypi.blogspot.com");
        
        //the total amount of memory in the Java virtual machine
        long totalMem = Runtime.getRuntime().totalMemory();
        //the maximum amount of memory that the Java virtual machine will attempt to use
        long maxMem = Runtime.getRuntime().maxMemory();
        //the amount of free memory in the Java Virtual Machine
        long freeMem = Runtime.getRuntime().freeMemory();
        
        System.out.println("totalMemory() - " + totalMem);
        System.out.println("maxMemory() - " + maxMem);
        System.out.println("freeMemory() - " + freeMem);
        
    }
    
}

We can run java with -Xms and -Xmx options to set Java heap size:
  • -Xms<size> set initial Java heap size
  • -Xmx<size> set maximum Java heap size

Run on Raspberry Pi:

Friday, April 18, 2014

How can I become a good programmer

"Everybody in this country should learn how to program a computer...
because it teaches you how to think" ~ Steve Jobs

A motivational video for new beginner programmers by industrialist and entertainers like: bill gates, larry wall, mark zuckerberg and will i am.

Thursday, April 17, 2014

Raspberry Pi Takes a Swim!

Raspberry Pi submerged in mineral Oil!
***NOTE: DO NOT USE WATER, ONLY MINERAL OIL!

Tuesday, April 15, 2014

The MagPi magazine, issue Apr 2014 released

The new The MagPi magazine, issue 22, Apr 2014 released, visit http://www.themagpi.com/issue/issue-22/ to download.

Upload file using Node.js with formidable

This example implement web app using Node.js with formidable. formidable is a node.js module for parsing form data, especially file uploads. By default, the uploaded file will be aved in /tmp directory.

To install formidable, run the command in your working directory:
$ npm install formidable

Example code, app.js (tested on Raspberry Pi and Ubuntu):
// run the command to install formidable
// $ npm install formidable
var formidable = require('formidable');
var http = require('http');
var util = require('util');
var fs = require('fs');
var os = require('os');

var app = http.createServer(
 function(req, res){
  switch(req.method){
   case 'GET':
    showPage(req, res);
    break;
   case 'POST':
    upload(req, res);
    break;
  }
 }
);
app.listen(8080);

//Display my IP
var networkInterfaces=os.networkInterfaces();

for (var interface in networkInterfaces) {
    
    networkInterfaces[interface].forEach(
        function(details){
            
            if (details.family=='IPv4' 
                && details.internal==false) {
                    console.log(interface, details.address);  
        }
    });
}

function showPage(req, res){
 fs.readFile(__dirname + '/index.html',
  function (err, data) {
   if (err) {
    res.writeHead(500);
    return res.end('Error loading index.html');
   }
  
   res.writeHead(200);
   res.end(data); 
  });
}

function upload(req, res){

 var form = new formidable.IncomingForm();
 
 form.parse(req, function(err, fields, files) {
  res.writeHead(200, {'content-type': 'text/plain'});
  res.end('File uploaded!');
  console.log("Upload completed");
  console.log(util.inspect(files));
 });
 
}

index.html
<html>
<head></head>
<body>
<h1>Upload file</h1>
<h1>Test Node.js with formidable</h1>
<div>
<form action="/upload" enctype="multipart/form-data" method="post">
<input type="file" name="file"><br>
<input type="submit" value="Upload">
</form>
</div>

</body>
</html>

Upload file using Node.js with formidable, tested on Raspberry Pi.

Learning Python with Raspberry Pi



Learning Python with Raspberry Pi

The must-have companion guide to the Raspberry Pi User Guide!
Raspberry Pi chose Python as its teaching language of choice to encourage a new generation of programmers to learn how to program. This approachable book serves as an ideal resource for anyone wanting to use Raspberry Pi to learn to program and helps you get started with the Python programming language. Aimed at first-time developers with no prior programming language assumed, this beginner book gets you up and running.
  • Covers variables, loops, and functions
  • Addresses 3D graphics programming
  • Walks you through programming Minecraft
  • Zeroes in on Python for scripting
Learning Python with Raspberry Pi proves itself to be a fantastic introduction to coding.

March 10, 2014  1118717058  978-1118717059 1



Sunday, April 13, 2014

Install Bluefish Editor on Raspberry Pi

Bluefish Editor is a powerful editor targeted towards programmers and webdevelopers, with many options to write websites, scripts and programming code. Bluefish supports many programming and markup languages. Bluefish is an open source development project, released under the GNU GPL licence.

To install bluefish on Raspberry Pi, run the command:
$ sudo apt-get install bluefish



Tuesday, April 8, 2014

Internet of Things, Java and Raspberry Pi

In this session, we invited Oracle engineer Gary Collins, who is responsible for testing and running Java SE Embedded in many many different types of boards, single board computers, plug computers and other. Vinicius Senger and Gary Collins will be talking about IoT and how all those different types of small computers can help us to implement nice solutions. Gary will be showing about at least 10 different computers and they will be sharing experiences like the JavaOne 2013 chess machine and Vinicius's new project involving sailing boats and IoT!

Internet of Things, Java and Raspberry Pi

Wednesday, April 2, 2014

Download Java ME Embedded Getting Started Guide

The Beta Draft of Java ME Embedded Getting Started Guide for Java ME Embedded 8 Early Access Release published.

Support Platforms included:
  • Qualcomm IoE: describes how to install and run the Oracle Java ME Embedded software on the Qualcomm IoE reference platform.
  • Raspberry Pi: describes how to install and run the Oracle Java ME Embedded software on the Raspberry Pi reference platform.
  • Windows (via Java ME SDK): describes how to use Oracle Java ME SDK 8 EA 2 to develop embedded applications, using the NetBeans 8.0 Beta Integrated Development Environment, on a Windows 7 platform.



Related:
Introduction of Java ME Embedded 8


Introduction of Java ME Embedded 8

This video introduce how to become an Embedded Developer using Java ME Embedded 8.
  • Introduce background and overview of Java Micro Edition (ME) 8
  • Getting started with Hardware (Raspberry Pi), Software (APIs) and Tools (Netbeans) to develop application for Raspberry Pi.
  • Examples of using GPIO and I2C.
  • Conclusion


Be an Embedded Developer in Minutes Using Java ME Embedded 8

Jump into the new wave of machine-to-machine technology and the Internet of Things (IoT) with Java ME Embedded 8. The session will provide the know-how to become an embedded Java developer in minutes.