How do I replace characters in string?

By Wayan in Core API, Lang Package 0 Comment 
package org.kodejava.lang;

public class StringReplace {
    public static void main(String[] args) {
        String text = "The quick brown fox jumps over the lazy dog";
        System.out.println("Before: " + text);

        // The replace method replace all occurrences of character
        // 'o' with 'u' and returns a new string object.
        text = text.replace('o', 'u');
        System.out.println("After : " + text);
    }
}

The result of the code snippet:

Before: The quick brown fox jumps over the lazy dog
After : The quick bruwn fux jumps uver the lazy dug

How do I copy char array to string?

By Wayan in Core API, Lang Package 0 Comment 
package org.kodejava.lang;

public class CharArrayCopyExample {
    public static void main(String[] args) {
        char[] data = {'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j'};

        // Copy all value in the char array and create a new string out of it.
        String text = String.valueOf(data);
        System.out.println(text);

        // Copy a sub array from the char array and create a new string. The
        // following line will just copy 5 characters starting from array index
        // of 3. If the element copied is outside the array index an
        // IndexOutOfBoundsException will be thrown.
        text = String.copyValueOf(data, 3, 5);
        System.out.println(text);
    }
}

The result:

abcdefghij
defgh

How do I remove leading and trailing white space from string?

By Wayan in Core API, Lang Package 0 Comment 
package org.kodejava.lang;

public class TrimStringExample {
    public static void main(String[] args) {
        String text = "     tattarrattat     ";
        System.out.println("Original      = " + text);
        System.out.println("text.length() = " + text.length());

        // The trim() method will result a new string object with a leading and
        // trailing while space removed.
        text = text.trim();
        System.out.println("Result        = " + text);
        System.out.println("text.length() = " + text.length());
    }
}

The result of the code snippet above:

Original      =      tattarrattat     
text.length() = 22
Result        = tattarrattat
text.length() = 12

How do I format a number with leading zeros?

By Wayan in Core API, Text Package 0 Comment

This example give you an example using java.text.DecimalFormat class to add leading zeros to a number. For another method you can read the see the earlier example on How do I add leading zeros to a number?.

package org.kodejava.text;

import java.text.DecimalFormat;
import java.text.NumberFormat;

public class NumberFormatLeadingZerosExample {
    public static void main(String[] args) {
        NumberFormat formatter = new DecimalFormat("0000000");
        String number = formatter.format(2500);

        System.out.println("Number with leading zeros: " + number);
    }
}

The result of code snippet above:

Number with leading zeros: 0002500

How do I add leading zeros to a number?

By Wayan in Core API, Lang Package 1 Comment

This example shows you how to use the String.format() method to add zero padding to a number. If you just want to print out the result you can use System.out.format(). This method is available since Java 1.5, so If you use a previous version you can use the NumberFormat class, see: How do I format a number with leading zeros?.

package org.kodejava.lang;

public class LeadingZerosExample {
    public static void main(String[] args) {
        int number = 1500;

        // String format below will add leading zeros (the %0 syntax)
        // to the number above. The length of the formatted string will
        // be 7 characters.
        String formatted = String.format("%07d", number);

        System.out.println("Number with leading zeros: " + formatted);
    }
}

Here is the result of the code snippet above:

Number with leading zeros: 0001500

For more information about the format syntax you can find it here.

How do I create a batch update in JDBC?

By Wayan in JDBC 0 Comment

A batch statement can be used to execute multiple update commands as single unit in a database manipulation. This statement in the database is not executed one by one but as a single execution instead. In some cases, using a batch update can be more efficient than to execute the commands separately.

In this example, you are shown how to create a batch command to insert some products into a database table.

package org.kodejava.jdbc;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.Arrays;

public class JDBCBatchExample {
    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 connection =
                     DriverManager.getConnection(URL, USERNAME, PASSWORD)) {

            // Turn of the auto-commit mode
            connection.setAutoCommit(false);

            try (Statement statement = connection.createStatement()) {
                // And some batch to insert some product information into
                // the product table
                statement.addBatch("INSERT INTO product (code, name) " +
                                   "VALUE ('P0000006', 'Championship Manager')");
                statement.addBatch("INSERT INTO product (code, name) " +
                                   "VALUE ('P0000007', 'Transport Tycoon Deluxe')");
                statement.addBatch("INSERT INTO product (code, name) " +
                                   "VALUE ('P0000008', 'Roller Coaster Tycoon 3')");
                statement.addBatch("INSERT INTO product (code, name) " +
                                   "VALUE ('P0000009', 'Pro Evolution Soccer')");

                // To execute a batch command, we must call the executeBatch()
                // method.
                int[] updateCounts = statement.executeBatch();
                System.out.println("updateCounts = " + Arrays.toString(updateCounts));

                // Commit our transaction
                connection.commit();
            } catch (SQLException e) {
                connection.rollback();
                e.printStackTrace();
            }
        } 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

How do I read an applet parameters?

By Wayan in Applet, Core API 0 Comment 
package org.kodejava.applet;

import java.applet.Applet;
import java.awt.Color;
import java.awt.Graphics;

public class AppletParameterExample extends Applet {
    private String name = "";

    public void init() {
        // Here we read a parameter named name from the applet tag definition
        // in our html file.
        name = getParameter("name");
    }

    public void paint(Graphics g) {
        g.setColor(Color.BLUE);
        g.drawString("Hello " + name + ", Welcome to the Applet World.", 0, 0);
    }
}

Now we have the applet code ready. To enable the web browser to execute the applet create the following html page.

<!DOCTYPE html>
<html lang="en">
<head>
    <title>Parameterized Applet</title>
</head>
<body>
<applet code="org.kodejava.applet.AppletParameterExample"
        height="150" width="350">
    <param name="name" value="Mr. Bean"/>
</applet>
</body>
</html>
** Deprecated: The Applet API is deprecated since JDK 9, no replacement.

How do I convert string date to long value?

By Wayan in Core API, Util Package 0 Comment 
package org.kodejava.util;

import java.text.DateFormat;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;

public class StringDateToLong {
    public static void main(String[] args) {
        // Here we have a string date, and we want to covert it to long value
        String today = "25/09/2021";

        // Create a SimpleDateFormat which will be used to convert the string to
        // a date object.
        DateFormat formatter = new SimpleDateFormat("dd/MM/yyyy");
        try {
            // The SimpleDateFormat parse the string and return a date object.
            // To get the date in long value just call the getTime method of
            // the Date object.
            Date date = formatter.parse(today);
            long dateInLong = date.getTime();

            System.out.println("Date         = " + date);
            System.out.println("Date in Long = " + dateInLong);
        } catch (ParseException e) {
            e.printStackTrace();
        }
    }
}

The result of the code snippet:

Date         = Sat Sep 25 00:00:00 CST 2021
Date in Long = 1632499200000

How do I create a scrollable result sets?

By Wayan in JDBC 0 Comment

Since JDBC 2.0 (JDK 1.2), a scrollable ResultSet was introduced to the java.sql API family. Using this ResultSet enables us to navigate the result set in forward or backward way.

To enable the scrollable ResultSet, we need to create a statement object by defining the ResultSet type (ResultSet.TYPE_SCROLL_SENSITIVE, ResultSet.TYPE_SCROLL_INSENSITIVE). If you define the ResultSet type to ResultSet.TYPE_FORWARD_ONLY then you get a regular ResultSet where you can move forward only as in JDBC 1.0

package org.kodejava.jdbc;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

public class ScrollableResultSetExample {
    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 connection =
                     DriverManager.getConnection(URL, USERNAME, PASSWORD)) {

            Statement statement = connection.createStatement(
                    ResultSet.TYPE_SCROLL_INSENSITIVE,
                    ResultSet.CONCUR_READ_ONLY);

            // This result set is a scrollable result set
            String query = "SELECT * FROM product";
            ResultSet resultSet = statement.executeQuery(query);
            while (resultSet.next()) {
                System.out.println(resultSet.getString("code"));
            }
        } 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

How do I move to absolute or relative row?

By Wayan in JDBC 0 Comment

In this example we are showing you how to use result set absolute() and relative() method to jump from one result set row to the other. When you pass a positive number as the parameter, you’ll move from the first record to the last. But if you pass a negative number as parameter, you’ll move from the last record backward.

package org.kodejava.jdbc;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

public class MoveAbsoluteOrRelativeExample {
    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 connection =
                     DriverManager.getConnection(URL, USERNAME, PASSWORD)) {

            Statement statement = connection.createStatement(
                    ResultSet.TYPE_SCROLL_INSENSITIVE,
                    ResultSet.CONCUR_READ_ONLY);

            String sql = "SELECT id, code, name, price FROM product";
            ResultSet rs = statement.executeQuery(sql);

            // Move to the second row
            rs.absolute(2);
            System.out.println("You are now in: " + rs.getRow());

            // Move 2 records forward from the current position 
            // (fourth row)
            rs.relative(2);
            System.out.println("You are now in: " + rs.getRow());

            // Move to the last row in the result set
            rs.absolute(-1);
            System.out.println("You are now in: " + rs.getRow());

            // Move 3 records backward from the current position 
            // (second row)
            rs.relative(-3);
            System.out.println("You are now in: " + rs.getRow());
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
}

The code output the following result:

You are now in: 2
You are now in: 4
You are now in: 5
You are now in: 2

Maven Dependencies

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

Maven Central