How do I get the name of current executed method?

package org.kodejava.lang;

public class GetCurrentMethodName {
    public static void main(String[] args) {
        // Get the current executing method name
        String methodName =
                Thread.currentThread().getStackTrace()[1].getMethodName();
        System.out.println("methodName = " + methodName);

        GetCurrentMethodName obj = new GetCurrentMethodName();
        obj.executeAMethod();
    }

    private void executeAMethod() {
        // Get the current executing method name
        String methodName =
                Thread.currentThread().getStackTrace()[1].getMethodName();
        System.out.println("methodName = " + methodName);
    }
}

This program will print out the following string:

methodName = main
methodName = executeAMethod

How do I convert java.util.Date to java.sql.Date?

package org.kodejava.jdbc;

import java.util.Date;

public class UtilDateToSqlDate {
    public static void main(String[] args) {
        // Create a new instance of java.util.Date
        Date date = new Date();

        // To covert java.util.Date to java.sql.Date we need to
        // create an instance of java.sql.Date and pass the long
        // value of java.util.Date as the parameter.
        java.sql.Date sqlDate = new java.sql.Date(date.getTime());

        System.out.println("Date    = " + date);
        System.out.println("SqlDate = " + sqlDate);
    }
}

The result of the code snippet above:

Date    = Sat Oct 09 20:23:27 CST 2021
SqlDate = 2021-10-09

How do I remove an attribute from XML element in JDOM?

The following example shows you how to remove attributes from an XML element. We will remove attribute named userid from the <row> element. To remove an attribute you can call the removeAttribute(String name) method of the Element object.

package org.kodejava.jdom;

import org.jdom2.Document;
import org.jdom2.Element;
import org.jdom2.input.SAXBuilder;
import org.jdom2.output.Format;
import org.jdom2.output.XMLOutputter;

import java.io.File;

public class JDOMRemoveAttribute {
    public static void main(String[] args) {
        SAXBuilder builder = new SAXBuilder();
        try {
            // <?xml version="1.0" encoding="UTF-8"?>
            // <root>
            //     <row userid="alice">
            //         <firstname>Alice</firstname>
            //         <lastname>Starbuzz</lastname>
            //     </row>
            // </root>
            Document doc = builder.build(new File("data.xml"));
            XMLOutputter out = new XMLOutputter(Format.getPrettyFormat());
            out.output(doc, System.out);

            // Get the root element and find a child named row and remove
            // its attribute named "userid"
            Element root = doc.getRootElement();
            root.getChild("row").removeAttribute("userid");
            out.output(doc, System.out);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

The program will output the following result to the console:

<?xml version="1.0" encoding="UTF-8"?>
<data>
  <row>
    <username>alice</username>
    <password>secret</password>
  </row>
</data>
<?xml version="1.0" encoding="UTF-8"?>
<data>
  <row>
    <username>alice</username>
    <password>secret</password>
  </row>
</data>

Maven Dependencies

<dependency>
    <groupId>org.jdom</groupId>
    <artifactId>jdom2</artifactId>
    <version>2.0.6.1</version>
</dependency>

Maven Central

How do I remove an element from XML document in JDOM?

This example show you how to remove an element from XML document. In the code snippet below we start by loading an XML document and display its original contents. After that we find the element <row>, and remove the <address> element from it. To get the first child we are using the getChild() method from the root Element object. To remove an element we use the removeChild() method.

package org.kodejava.jdom;

import org.jdom2.Document;
import org.jdom2.input.SAXBuilder;
import org.jdom2.output.Format;
import org.jdom2.output.XMLOutputter;

import java.io.File;

public class JDOMRemoveElement {
    public static void main(String[] args) {
        SAXBuilder builder = new SAXBuilder();
        try {
            Document doc = builder.build(new File("userinfo.xml"));

            // The lines below output the original userinfo.xml content
            //
            // <?xml version="1.0" encoding="UTF-8"?>
            // <rows>
            //   <row>
            //     <firstname>Alice</firstname>
            //     <lastname>Mallory</lastname>
            //     <address>Sunset Road</address>
            //   </row>
            // </rows>
            XMLOutputter out = new XMLOutputter(Format.getPrettyFormat());
            out.output(doc, System.out);

            // Remove the address element from Alice information. First we
            // get the row element from the root element, and finally 
            // remove the address from the row. And the result will be:
            //
            // <?xml version="1.0" encoding="UTF-8"?>
            // <rows>
            //   <row>
            //     <firstname>Alice</firstname>
            //     <lastname>Mallory</lastname>
            //   </row>
            // </rows>
            doc.getRootElement().getChild("row").removeChild("address");
            out.output(doc, System.out);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

The code snippet print the following output:

<?xml version="1.0" encoding="UTF-8"?>
<rows>
  <row>
    <firstname>Alice</firstname>
    <lastname>Starbuzz</lastname>
    <address>Sunset Road</address>
  </row>
</rows>
<?xml version="1.0" encoding="UTF-8"?>
<rows>
  <row>
    <firstname>Alice</firstname>
    <lastname>Starbuzz</lastname>
  </row>
</rows>

Maven Dependencies

<dependency>
    <groupId>org.jdom</groupId>
    <artifactId>jdom2</artifactId>
    <version>2.0.6.1</version>
</dependency>

Maven Central

How do I add attributes to an XML elements in JDOM?

The program below will show you how to add attributes to an XML elements. Using JDOM library this can be easily done by calling the Element‘s setAttribute(String name, String value) method.

package org.kodejava.jdom;

import org.jdom2.Document;
import org.jdom2.Element;
import org.jdom2.output.Format;
import org.jdom2.output.XMLOutputter;

public class JDOMAddAttribute {
    public static void main(String[] args) {
        Document doc = new Document();
        Element root = new Element("root");

        // Create <row userid="alice"></row>
        Element child = new Element("row").setAttribute("userid", "alice");

        // Create <name firstname="Alice" lastname="Starbuzz"></name>
        Element name = new Element("name")
                .setAttribute("firstname", "Alice")
                .setAttribute("lastname", "Starbuzz");

        child.addContent(name);
        root.addContent(child);
        doc.addContent(root);

        XMLOutputter outputter = new XMLOutputter(Format.getPrettyFormat());
        try {
            outputter.output(doc, System.out);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

And here goes the output:

<?xml version="1.0" encoding="UTF-8"?>
<root>
  <row userid="alice">
    <name firstname="Alice" lastname="Starbuzz" />
  </row>
</root>

Maven Dependencies

<dependency>
    <groupId>org.jdom</groupId>
    <artifactId>jdom2</artifactId>
    <version>2.0.6.1</version>
</dependency>

Maven Central

How do I create an XML document using JDOM?

In this small program you can see how to use JDOM to create a simple xml file. Below you’ll see how to create elements of the xml document, set some text for the element.

After that you can see how to use the XMLOutputter class to write the JDOM document into file and display it on the screen. To make the output better we can apply a Format to our xml document.

package org.kodejava.jdom;

import org.jdom2.Document;
import org.jdom2.Element;
import org.jdom2.output.Format;
import org.jdom2.output.XMLOutputter;

import java.io.FileWriter;

public class JDomCreatingXml {
    public static void main(String[] args) {
        // <rows>
        //     <row>
        //         <firstname>Alice</firstname>
        //         <lastname>Starbuzz</lastname>
        //         <address>Sunset Road</address>
        //     </row>
        // </row>
        Document document = new Document();
        Element root = new Element("rows");

        // Creating a child for the root element. Here we can see how to
        // set the text of an xml element.
        Element child = new Element("row");
        child.addContent(new Element("firstname").setText("Alice"));
        child.addContent(new Element("lastname").setText("Starbuzz"));
        child.addContent(new Element("address").setText("Sunset Road"));

        // Add the child to the root element and add the root element as
        // the document content.
        root.addContent(child);
        document.setContent(root);

        try {
            FileWriter writer = new FileWriter("userinfo.xml");
            XMLOutputter outputter = new XMLOutputter();

            // Set the XLMOutputter to pretty formatter. This formatter
            // use the TextMode.TRIM, which mean it will remove the
            // trailing white-spaces of both side (left and right)
            outputter.setFormat(Format.getPrettyFormat());

            // Write the document to a file and also display it on the
            // screen through System.out.
            outputter.output(document, writer);
            outputter.output(document, System.out);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

This program will output the following XML document:

<?xml version="1.0" encoding="UTF-8"?>
<rows>
  <row>
    <firstname>Alice</firstname>
    <lastname>Starbuzz</lastname>
    <address>Sunset Road</address>
  </row>
</rows>

Maven Dependencies

<dependency>
    <groupId>org.jdom</groupId>
    <artifactId>jdom2</artifactId>
    <version>2.0.6.1</version>
</dependency>

Maven Central

How do I create a Document object in JDOM?

The following example show you how to create a simple Document object in JDOM. We can create a new document directly by creating a new instance of the Document class, for additional information we can pass an Element as an argument.

To create a Document from an existing XML file we can use the SAXBuilder. Beside reading from file we can also build a Document from stream and URL.

package org.kodejava.jdom;

import org.jdom2.Document;
import org.jdom2.Element;
import org.jdom2.input.SAXBuilder;

import java.io.File;

public class JDOMCreateDocument {
    public static void main(String[] args) {
        // Creating a document with an Element as the parameter.
        Element element = new Element("root");
        element.setText("Hello World");

        Document document = new Document(element);
        System.out.println("root.getName() = " +
                document.getRootElement().getName());

        // We can also create a document from a file, stream or URL using
        // a SAXBuilder
        SAXBuilder builder = new SAXBuilder();
        try {
            // Build a document from a file using a SAXBuilder.
            // The content of data.xml file:
            //
            // <?xml version="1.0" encoding="UTF-8"?>
            // <data>
            //     <row>
            //         <username>alice</username>
            //         <password>secret</password>
            //     </row>
            // </data>
            document = builder.build(new File("data.xml"));
            Element root = document.getRootElement();
            System.out.println("root.getName() = " + root.getName());
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

Maven Dependencies

<dependency>
    <groupId>org.jdom</groupId>
    <artifactId>jdom2</artifactId>
    <version>2.0.6.1</version>
</dependency>

Maven Central

How do I get the items of a JList components?

In this example you can see how we can read the items of a JList component. We also obtain the size or the number of items in the JList components.

This can be done by calling JList‘s getModel() method which return a ListModel object. From the ListModel we can get the items size, and we can iterate the entire items of the JList component.

package org.kodejava.swing;

import javax.swing.*;
import java.awt.*;
import java.text.DateFormatSymbols;

public class JListGetItems extends JFrame {
    public JListGetItems() {
        initialize();
    }

    public static void main(String[] args) {
        // Run the program, create a new instance of JListGetItems and
        // set its visibility to true.
        SwingUtilities.invokeLater(
                () -> new JListGetItems().setVisible(true));
    }

    private void initialize() {
        // Configure the frame default close operation, its size and the
        // layout.
        this.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
        this.setSize(500, 500);
        this.setLayout(new BorderLayout(5, 5));

        // Create a JList and set the items to the available weekdays
        // names.
        Object[] listItems = DateFormatSymbols.getInstance().getWeekdays();
        JList<Object> list = new JList<>(listItems);
        getContentPane().add(list, BorderLayout.CENTER);

        // Below we start to print the size of the list items and iterates
        // the entire list items or elements.
        System.out.println("JList item size: " + list.getModel().getSize());

        System.out.println("Reading all JList items:");
        System.out.println("-----------------------");
        for (int i = 0; i < list.getModel().getSize(); i++) {
            Object item = list.getModel().getElementAt(i);
            System.out.println("Item = " + item);
        }
    }
}

And here is the result:

JList item size: 8
Reading all JList items:
-----------------------
Item = 
Item = Sunday
Item = Monday
Item = Tuesday
Item = Wednesday
Item = Thursday
Item = Friday
Item = Saturday

How do I set the cell width and height of a JList component?

The cell width and height of a JList can be defined by setting the fixedCellWidth and fixedCellHeight properties. These properties have a corresponding methods called setFixedCellWidth(int width) and setFixedCellHeight(int height).

package org.kodejava.swing;

import javax.swing.*;
import java.awt.*;
import java.util.Vector;

public class JListCellWidthAndHeight extends JFrame {
    public JListCellWidthAndHeight() {
        initialize();
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(
                () -> new JListCellWidthAndHeight().setVisible(true));
    }

    private void initialize() {
        // Initialize windows default close operation, size and the layout
        // for laying the components.
        setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
        setSize(500, 175);
        setLayout(new BorderLayout(5, 5));

        // Create a list of vector data to be used by the JList component.
        Vector<String> v = new Vector<>();
        v.add("A");
        v.add("B");
        v.add("C");
        v.add("D");

        JList<String> list = new JList<>(v);
        list.setFixedCellWidth(50);
        list.setFixedCellHeight(50);

        JScrollPane pane = new JScrollPane(list);

        // Add an action listener to the button to exit the application.
        JButton button = new JButton("CLOSE");
        button.addActionListener(e -> System.exit(0));

        // Add the scroll pane where the JList component is wrapped and
        // the button to the center and south of the panel
        getContentPane().add(pane, BorderLayout.CENTER);
        getContentPane().add(button, BorderLayout.SOUTH);
    }
}
JList Cell Width and Height Demo

JList Cell Width and Height Demo

How do I create a JList component?

JList is a component that displays a list of objects and allow user to select one or more items. To create an instance of JList we can pass a vector, an array of objects or a ListModel. In this example we will pass an array of objects that contains a date, string and numbers as the parameters.

By default, the list does not display a scrollbar. To give our JList component a scrollbar we must wrap it with a JScrollPane.

package org.kodejava.swing;

import javax.swing.*;
import java.awt.*;
import java.util.Date;

public class CreateJListDemo extends JFrame {

    public CreateJListDemo() {
        initialize();
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(
                () -> new CreateJListDemo().setVisible(true));
    }

    // Initialize the components and configuration of our CreateJListDemo.
    private void initialize() {
        // Define the window title, size and the default close operation.
        this.setTitle("Create JList Demo");
        this.setSize(500, 175);
        this.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);

        // Create an array of arbitrary objects for the JList to display.
        Object[] data = new Object[]{
                new Date(), "One", 1, Long.valueOf("12345"), "Four", "Five"
        };

        // Create an instance of JList and pass data variable as the
        // initial content of it. By default, the JList does not have a
        // scrolling behaviour, so we create a JScrollPane as the container
        // for the JList.
        JList<Object> list = new JList<>(data);
        JScrollPane scrollPane = new JScrollPane(list);

        // Add a button to close the program.
        JButton button = new JButton("Close");
        button.addActionListener(e -> System.exit(0));

        // Set the panel layout to BorderLayout and place the list in the
        // center and the button on the south.
        this.setLayout(new BorderLayout(5, 5));
        getContentPane().add(scrollPane, BorderLayout.CENTER);
        getContentPane().add(button, BorderLayout.SOUTH);
    }
}
Swing JList Demo

Swing JList Demo