Posts in the “java” category

Java Mail (JavaMail) IMAP FAQ: Can you show me how to get a list of all the email addresses in an IMAP mailbox using the Java Mail API (JavaMail API)?

Sure. Here's the source code for a Java mail (JavaMail) program that extracts all of the "from" fields out of a specified mailbox. This works for both POP3 and IMAP mailboxes.

Before going to the code, note the cool use of a TreeSet (java.util.TreeSet) in this example. Based on our offline discussion, you mentioned that you really want is this:

Wow, I haven't worked with images in Java in a while, and it turns out that opening and reading an image file in Java is very easy these days. Just use the read method of the Java ImageIO class, and you can open/read images in a variety of formats (GIF, JPG, PNG) in basically one line of Java code.

Recently I was asked "How can I maximize a frame (JFrame) in Java?"

Like a lot of things, once you know how to do it, it turns out to be pretty easy.

How to maximize a JFrame

Here's some code that shows how to maximize a JFrame:

Just read that JavaFX is going to be removed from the Java JDK. From the article: “Making JavaFX its own module will make it easier to adopt and clear the way for new contributors, Oracle said. The company added that with the faster release schedule being implemented for standard Java and the JDK, JavaFX needs to be on its own pace driven by contributions from Oracle and others in the OpenJFX community.”

Java keytool export FAQ: Can you share some examples of the Java keytool export command and export process?

Once you've created a private key in a Java keystore file, you can export that private key to a certificate file using the Java "keytool export" command. I'll demonstrate that command in this tutorial.

Java “keytool list” FAQ: Can you share some examples of the Java keytool list command, and Java keytool list process?

In a long, earlier article on Java keytool, keystore, and certificates, I demonstrated how to list the contents of a Java keystore file, but to simplify things a little for this tutorial, I'm just going to show how to query a Java keystore file using the keytool list command.

Java AppleScript FAQ: How can I run a multiline AppleScript script from a Java application?

If you ever need to run a multi-line Applescript command from a Java program, fear not, it can be done.

A Java AppleScript example

Here's an example of some Java code that runs multiple lines of Applescript, six to be precise:

Question: How do I convert a String to a double with Java?

Answer: Converting a String to a double requires that you first convert the String to a Double object, then convert the Double object to a double data type (Double is an object, while double is a primitive data type).

Here's the source code for an example Java program that performs this conversion:

As I was digging around through some code today, I found the following Java Random class example, and thought I'd share it here for anyone needed to see how to work with the Random class in Java. This example shows how to generate a random number in Java that is greater than or equal to 0, and less than 100:

With custom icon

It’s important to note that you can also customize the icon that is displayed when using a JOptionPane showMessageDialog. In the following example, I specify that I want to display my own PNG image as an icon on the dialog by creating an ImageIcon as an additional argument to the showMessageDialog method:

On this blog I've shown a variety of ways using Java to open a URL connection, and then read data from that connection, including my "How to open and read from a URL with the Java URL and URLConnection classes" tutorial. In this example I'll show how to open a URL using the Java HttpURLConnection class.

Java String/float FAQ: How do I convert a Java String to a float?

Converting a String to a float requires that you first convert the String to a Float object, then convert the Float object to a float data type (Float is an object, while float is a primitive data type).

An example of a simple program that performs this conversion is shown below:

Java keytool genkey FAQ: Can you share some examples of the Java keytool genkey command, and genkey process?

In my previous article on the Java keytool command, keystore files, and certificates, I demonstrated how to generate a private key with the keytool genkey option, but to simplify things a little, I thought I'd demonstrate the keytool genkey command again here by itself.

I've been working with the Java keytool command a lot lately, as I needed to learn all about it to license my "Hide your desktop icons" app with the TrueLicense software license manager. I think I've learned a lot about the Java keytool command, keystore files, and certificates, and I'm trying to simplify and share that information here.

I’m currently doing something completely different, and writing a little custom web browser using JavaFX and its WebView component. I’m using it so I can easily look at stock quotes and charts. I just started on it, and the current UI looks like this:

I just started working with LibGDX, so I don’t know if there’s a better way to create a LibGDX Scene2d ImageButton, but I can confirm that this approach works:

Texture hikeTexture = new Texture(Gdx.files.internal("hike_btn.jpg"));
Texture hikeTexturePressed = new Texture(Gdx.files.internal("hike_btn_pressed.jpg"));
hikeButton = new ImageButton(
    new TextureRegionDrawable(new TextureRegion(hikeTexture)),
    new TextureRegionDrawable(new TextureRegion(hikeTexturePressed))
);
hikeButton.setPosition(60, 300);  //hikeButton is an ImageButton
stage.addActor(hikeButton);

I currently use this code in the show() method of a class that implements Screen, and it works as desired.

Here's a step-by-step approach for how to implement "undo" and "redo" behavior in your Java text components, i.e., the JTextArea JEditorPane and JTextPane I should note that you don't get this behavior for free -- you have to implement it yourself, hence this undo/redo tutorial.

If you ever need to display an image in a Java JEditorPane, where that JEditorPane contains HTML content, this solution should work:

TypeAhead is a continuous predictive text editor. It always tries to help you auto-complete the current word by using words in (a) the current document, as well as (b) a dictionary.

This short video shows a very rough prototype of how this might work:

Improvements

A few improvements are possible and easy.

Java Swing FAQ: How do I create a menubar (and menu and menuitems) in Java?

As I was working on a Java/Swing problem last week, I was scouring through the Mac OS X Java-Dev mailing list, and along the way I ran into some really nice source code I thought I could modify into a decent Java Menubar example. After a little rewriting, here is that "Java Menubar" example.