Tag: Java - Page 2 - Catzie.net Blog

Android/Java: get variable data type

For some reason you might need to get the data type of your Java variable. Here’s an example of what you can try:

String date_created = “2016-02-04”;

String data_type = date_created.getClass().getSimpleName();

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String date_created = “2016-02-04”;

String data_type = date_created.getClass().getSimpleName();

Then do whatever you like with data_type, whose value should be “String”. 🙂

February 4, 2016

Get device’s IMEI in Android app development

Here’s the content of my MainActivity class where I log the IMEI of my test device.

package net.catzie.playground;

import android.content.Context;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.telephony.TelephonyManager;
import android.util.Log;

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        TelephonyManager telephonyManager = (TelephonyManager)getSystemService(Context.TELEPHONY_SERVICE);
        String deviceID = telephonyManager.getDeviceId();
        Log.d(“Device IMEI”, deviceID);
    }
}

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package net.catzie.playground;

import android.content.Context;

import android.support.v7.app.AppCompatActivity;

import android.os.Bundle;

import android.telephony.TelephonyManager;

import android.util.Log;

public class MainActivity extends AppCompatActivity {

@Override

protected void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.activity_main);

TelephonyManager telephonyManager = (TelephonyManager)getSystemService(Context.TELEPHONY_SERVICE);

String deviceID = telephonyManager.getDeviceId();

Log.d(“Device IMEI”, deviceID);

}

You also need to add this permission to your AndroidManifest.xml file:

<uses-permission android:name=”android.permission.READ_PHONE_STATE” />

1	<uses–permission android:name=“android.permission.READ_PHONE_STATE” />

Place it inside the <manifest></manifest> tag, but same level as <application></application>.

Source: How to get the device’s IMEI/ESN programmatically in android?

February 3, 2016

Android: open web page in a browser

To open a web page in an Android app, we need to create a new Intent and start a new Activity with it.

Here’s a Java method that we can re-use:

private void goToUrl (String url) {
        Uri uriUrl = Uri.parse(url);
        Intent launchBrowser = new Intent(Intent.ACTION_VIEW, uriUrl);
        startActivity(launchBrowser);
}

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private void goToUrl (String url) {

Uri uriUrl = Uri.parse(url);

Intent launchBrowser = new Intent(Intent.ACTION_VIEW, uriUrl);

startActivity(launchBrowser);

}

Just pass the URL of the web page you’d like to open to this method.

Source: How to open a website when a Button is clicked in Android application?

January 29, 2016

Android: 2-dimensional List String (List of List)

For a web developer who used mostly PHP and JavaScript for several years, plunging into Java can be challenging especially when it comes to data types.

PHP and JavaScript are loosely typed languages, while Java is strict about types.

I was told that in Android, List<String> is very commonly used, even more than arrays. And now I’ve come to the point when I need to use a 2-dimensional List<String>.

Here’s a sample code:

        List<List<String>> listOfList = new ArrayList<List<String>>();
        List<String> x = new ArrayList<String>();
        x.add(“Hello”);
        x.add(“world!”);
        listOfList.add(x);

        List<String> y = new ArrayList<String>();
        y.add(“1”);
        y.add(“4”);
        y.add(“3”);

        listOfList.add(y);

        for(List<String> ls : listOfList) {
            System.out.println(Arrays.deepToString(ls.toArray()));
        }

        Log.d(“serialized”, listOfList.toString());

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List<List<String>> listOfList = new ArrayList<List<String>>();

List<String> x = new ArrayList<String>();

x.add(“Hello”);

x.add(“world!”);

listOfList.add(x);

List<String> y = new ArrayList<String>();

y.add(“1”);

y.add(“4”);

y.add(“3”);

listOfList.add(y);

for(List<String> ls : listOfList) {

System.out.println(Arrays.deepToString(ls.toArray()));

}

Log.d(“serialized”, listOfList.toString());

Output of System.outprintln(Arrays.deepToString(ls.toArray())); is this:

I/System.out: [Hello, world!]
I/System.out: [1, 4, 3]

1 2	I/System.out: [Hello, world!] I/System.out: [1, 4, 3]

The output of Log.d("serialized", listOfList.toString()); is this:

D/serialized: [[Hello, world!], [1, 4, 3]]

1	D/serialized: [[Hello, world!], [1, 4, 3]]

December 14, 2015

Java: Strings

First off, if you are in need of a good Java programming reference book, I suggest that you try Head First Java.

In this blog entry, basics in Strings in Java programming will be briefly discussed.

Assumption: You have already set up your Java development kit on your computer. (Environmental Variables, paths, etc…)
(more…)

March 29, 2011

PDF Download: Head First Java (2nd Edition) – by Katy Sierra and Bert Bates

Learning Java? Great, this book will help you.

I uploaded this Java Programming PDF to share with IT Elective 1 (Object Oriented Programming with Java) classmates. 🙂

I searched for it in Google, and I’m lucky to find this free e-book of Head First Java – Second Edition. I can’t remember where I got it from though. It’s been days (EDIT: no, it’s been months now! or maybe years), and I got a poor memory. lol.

And by the way, I used A-PDF Split to split the e-book into separate chapters of the PDF for our convenience. The file I downloaded is only one PDF file which had 690 pages. It lags in slow computers. It’s also better off being separated by chapters for ease of reading, right? So, there. 😀

I hope the Java PDF download links on this blog entry (Head First Java – Download) help you guys, and if you do find them helpful, please LIKE my website on Facebook. To find it on Facebook, search for “Catzie.net” 😀

Download Link for Head First Java Ebook

New! The following Head First Java Ebook is of better quality than the scanned one. It’s not split into several PDFs of individual chapters though, because I have no time to do it yet. It’s one big PDF file for now.

FILE SIZE: 37.53MB

Head First Java (2nd Edition, Better Quality in One Big PDF) by Kathy Sierra and Bert Bates (Non-hotlinked from MediaFire) (unknown, 6,136 hits)

Download Links for Head First Java Ebook

The zip file that follows contains Head First Java scanned ebook split into several PDFs of individual chapters.
FILE SIZE: 31.6MB

Head First Java (2nd Edition, Scanned) by Kathy Sierra and Bert Bates (Non-hotlinked from MediaFire) (unknown, 2,418 hits)
Head First Java (2nd Edition, Scanned) by Kathy Sierra and Bert Bates (on FileDen) (unknown, 1,639 hits)

Java Book Chapters

Breaking the Surface: a quick dip
A Trip to Objectville: yes, there will be objects
Know Your Variables: primitives and references
How Objects Behave: object state affects method behavior
Extra-Strength Methods: flow control, operations, and more
Using the Java Library: so you don’t have to write it all yourself
Better Living in Objectville: planning for the future
Serious Polymorphism: exploiting abstract classes and interfaces
Life and Death of an Object: constructors and memory management
Numbers Matter: math, formatting, wrappers, and statics
Risky Behavior: exception handling
A Very Graphic Story: intro to GUI, event handling, and inner classes
Work on Your Swing: layout managers and components
Saving Objects: serialization and I/O
Make a Connection: networking sockets and multithreading
Data Structures: collections and generics
Release Your Code: packaging and deployment
Distributed Computing: RMI with a dash of servlets, EJB, and Jini

Happy Java programming, y’all. 🙂 Make good use of the learning Java book you downloaded.

Java is a programming language originally developed by James Gosling at Sun Microsystems (which is now a subsidiary of Oracle Corporation) and released in 1995 as a core component of Sun Microsystems’ Java platform.

The syntax of Java is mostly derived from that of C and C++ programming languages, but with simpler object model and fewer low-level facilities.

September 16, 2009