How do I use iText Chunk class?

By Wayan in iText PDF 0 Comment

A chunk com.itextpdf.text.Chunk is the smallest significant part that can be added to a document. A chunk is a string with Font information.

A chunk doesn’t add line breaks, a paragraph spacing or any other spacing. The layout parameters of a chunk should be defined in the object to which this chunk is added.

When you run this example the chunk will be written from left to right. But when it reaches the right edge of the document it will start writing another chunk from the left overwriting the previous chunk.

package org.kodejava.itextpdf;

import com.itextpdf.text.*;
import com.itextpdf.text.pdf.PdfWriter;

import java.io.FileNotFoundException;
import java.io.FileOutputStream;

public class ChunkDemo {
    public static void main(String[] args) {
        Document document = new Document();
        try {
            PdfWriter.getInstance(document,
                    new FileOutputStream("ChunkDemo.pdf"));
            document.open();

            // Add some chunks into the document object.
            document.add(new Chunk("The quick brown fox "));
            document.add(new Chunk("jumps over the lazy dog."));
            document.add(new Chunk("The quick brown fox "));
            document.add(new Chunk("jumps over the lazy dog."));
            document.add(new Chunk("The quick brown fox ",
                    FontFactory.getFont(FontFactory.HELVETICA, 20,
                            Font.ITALIC, new BaseColor(0, 128, 0))));
            document.add(new Chunk("jumps over the lazy dog."));
            document.close();
        } catch (DocumentException | FileNotFoundException e) {
            e.printStackTrace();
        } finally {
            document.close();
        }
    }
}

Maven Dependencies

<dependency>
    <groupId>com.itextpdf</groupId>
    <artifactId>itextpdf</artifactId>
    <version>5.5.13.3</version>
</dependency>

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How do I use iText Document class?

By Wayan in iText PDF 1 Comment

The com.itextpdf.text.Document is the core class of the iText library. This class represents a pdf document. Basically to work with a document we must first create an instance of a Document. After the instance created we open the document by calling the open() method. To add some content into the document we can use the add() method. Finally, after done with the document we must close it by calling the close() method.

If you need to write and flush the document into a file we can use a PdfWriter class. The class constructor accept a Document object and an OutputStream object to do the work.

package org.kodejava.itextpdf;

import com.itextpdf.text.Document;
import com.itextpdf.text.DocumentException;
import com.itextpdf.text.Paragraph;

public class DocumentDemo {
    public static void main(String[] args) {
        // Creates an instance of a Document.
        Document document = new Document();
        try {
            // To work with a Document we must open the document, add
            // some contents and finally close the document.
            document.open();
            document.add(new Paragraph("Hello World!"));
            document.close();
        } catch (DocumentException e) {
            e.printStackTrace();
        }
    }
}

Maven Dependencies

<dependency>
    <groupId>com.itextpdf</groupId>
    <artifactId>itextpdf</artifactId>
    <version>5.5.13.3</version>
</dependency>

Maven Central

How do I check whether a thread group has been destroyed?

By Wayan in Core API, Lang Package 0 Comment

You can use ThreadGroup.isDestroyed() method to check whether a thread group and its subgroups has been destroyed.

package org.kodejava.lang;

public class CheckGroupDestroy {
    public static void main(String[] args) {
        ThreadGroup grandParent = new ThreadGroup("GrandParent");
        ThreadGroup uncle = new ThreadGroup(grandParent, "Uncle");
        ThreadGroup parent = new ThreadGroup(grandParent, "Parent");
        ThreadGroup son = new ThreadGroup(parent, "Son");
        ThreadGroup daughter = new ThreadGroup(parent, "Daughter");
        ThreadGroup neighbour = new ThreadGroup("Neighbour");

        ThreadGroup[] groupArray = {
                grandParent, uncle, parent, son, daughter, neighbour
        };

        // Destroy 'parent' group and all its subgroups
        parent.destroy();

        // Check whether the group is destroyed. The result is,
        // GrandParent, Uncle, and Neighbour did not destroyed
        // because they are not Parent's subgroups
        for (ThreadGroup tg : groupArray) {
            if (tg.isDestroyed()) {
                System.out.println(tg.getName() + " is destroyed");
            } else {
                System.out.println(tg.getName() + " is not destroyed");
            }
        }
    }
}

The result is:

GrandParent is not destroyed
Uncle is not destroyed
Parent is destroyed
Son is destroyed
Daughter is destroyed
Neighbour is not destroyed

How do I destroy a thread group?

By Wayan in Core API, Lang Package 0 Comment

You can destroy a thread group by using destroy() method of ThreadGroup class. It will cleans up the thread group and removes it from the thread group hierarchy. It’s not only destroy the thread group, but also all its subgroups.

The destroy() method is of limited use: it can only be called if there are no threads presently in the thread group.

package org.kodejava.lang;

public class ThreadGroupDestroy {
    public static void main(String[] args) {
        ThreadGroup root = new ThreadGroup("Root");
        ThreadGroup server = new ThreadGroup(root, "ServerGroup");
        ThreadGroup client = new ThreadGroup(root, "ClientGroup");

        // Destroy 'root' thread groups and all its subgroup
        // ('server' & 'client')
        root.destroy();

        // Check if 'root' group and its subgroups already destroyed
        if (root.isDestroyed()) {
            System.out.println("Root group is destroyed");
        }

        if (server.isDestroyed()) {
            System.out.println("Server group is destroyed");
        }

        if (client.isDestroyed()) {
            System.out.println("Client group is destroyed");
        }
    }
}

How to automatically close resources in JDBC?

By Wayan in JDBC 0 Comment

One thing that we need to do manually when programming using JDBC is to make sure to close all the resources that we use. All resources including the ResultSet, Statement and Connection must be closed. This will usually produce a lot of boilerplate code in our program.

Starting from JDBC 4.1, which is a part of Java 7, we can use the try-with-resources statement to automatically manage the resources that we use. This try statement closes the resources used when the block finishes its execution either normally or abruptly.

Here is an example that shows us how to use the try-with-resources statement.

package org.kodejava.jdbc;

import java.sql.*;

public class TryWithResourceJdbc {
    private static final String URL = "jdbc:mysql://localhost/kodejava";
    private static final String USERNAME = "kodejava";
    private static final String PASSWORD = "s3cr*t";

    public static void main(String[] args) {
        try (Connection conn =
                     DriverManager.getConnection(URL, USERNAME, PASSWORD);
             Statement stmt = conn.createStatement();
             ResultSet rs = stmt.executeQuery("SELECT * FROM product")) {

            while (rs.next()) {
                String code = rs.getString("code");
                String name = rs.getString("name");

                System.out.println("Code: " + code + "; Name: " + name);
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
}

Maven Dependencies

<dependency>
    <groupId>com.mysql</groupId>
    <artifactId>mysql-connector-j</artifactId>
    <version>8.4.0</version>
</dependency>

Maven Central