How do I sort items of an ArrayList?

By Wayan in Core API, Util Package 0 Comment

This example shows you how we can sort items of an ArrayList using the Collections.sort() method. Beside accepting the list object to be sorted we can also pass a Comparator implementation to define the sorting behaviour such as sorting in descending or ascending order.

package org.kodejava.util;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.List;

public class ArrayListSortExample {
    public static void main(String[] args) {
        /*
         * Create a collections of colours
         */
        List<String> colours = new ArrayList<>();
        colours.add("red");
        colours.add("green");
        colours.add("blue");
        colours.add("yellow");
        colours.add("cyan");
        colours.add("white");
        colours.add("black");

        /*
         * We can sort items of a list using the Collections.sort() method.
         * We can also reverse the order of the sorting by passing the
         * Collections.reverseOrder() comparator.
         */
        Collections.sort(colours);
        System.out.println(Arrays.toString(colours.toArray()));

        colours.sort(Collections.reverseOrder());
        System.out.println(Arrays.toString(colours.toArray()));
    }
}

The code will output:

[black, blue, cyan, green, red, white, yellow]
[yellow, white, red, green, cyan, blue, black]

How do I sort array values in case-insensitive order?

By Wayan in Core API, Util Package 1 Comment

By default, when sorting an arrays the value will be ordered in case-sensitive order. This example show you how to order it in case-insensitive order.

package org.kodejava.util;

import java.util.Arrays;

public class SortArrayCaseSensitivity {
    public static void main(String[] args) {
        String[] teams = new String[5];
        teams[0] = "Manchester United";
        teams[1] = "chelsea";
        teams[2] = "Arsenal";
        teams[3] = "liverpool";
        teams[4] = "EVERTON";

        // Sort array, by default it will be sorted in case-sensitive order.
        // [Arsenal, EVERTON, Manchester United, chelsea, liverpool]
        Arrays.sort(teams);
        System.out.println("Case sensitive  : " + Arrays.toString(teams));

        // Sort array in case-insensitive order
        // [Arsenal, chelsea, EVERTON, liverpool, Manchester United]
        Arrays.sort(teams, String.CASE_INSENSITIVE_ORDER);
        System.out.println("Case insensitive: " + Arrays.toString(teams));
    }
}

The result of the code snippet above:

Case sensitive  : [Arsenal, EVERTON, Manchester United, chelsea, liverpool]
Case insensitive: [Arsenal, chelsea, EVERTON, liverpool, Manchester United]

How do I sort array values in descending order?

By Wayan in Core API, Util Package 0 Comment

Here you will find an example on how to sort the values of an array in ascending or descending order.

package org.kodejava.util;

import java.util.Arrays;
import java.util.Collections;

public class SortArrayWithOrder {
    public static void main(String[] args) {
        Integer[] points = new Integer[5];
        points[0] = 94;
        points[1] = 53;
        points[2] = 70;
        points[3] = 44;
        points[4] = 64;
        System.out.println("Original  : " + Arrays.toString(points));

        // Sort the points array, the default order is in ascending order.
        // [44, 53, 64, 70, 94]
        Arrays.sort(points);
        System.out.println("Ascending : " + Arrays.toString(points));

        // Sort the points array in descending order.
        // [94, 70, 64, 53, 44]
        Arrays.sort(points, Collections.reverseOrder());
        System.out.println("Descending: " + Arrays.toString(points));
    }
}

The result of the code snippet above are:

Original  : [94, 53, 70, 44, 64]
Ascending : [44, 53, 64, 70, 94]
Descending: [94, 70, 64, 53, 44]

How do I limit Hibernate query result?

By Wayan in Hibernate 0 Comment

In the example below you’ll see how to limit the number of records returned by hibernate queries. Limiting the query result is usually use for creating pagination, where we can navigate from page to page of data in our application but only a few of them are read from the database.

In hibernate Query object we need to specify the first result and max results by calling the setFirstResult() and setMaxResults() methods to limit the query results.

package org.kodejava.hibernate.service;

import org.hibernate.Session;
import org.hibernate.query.Query;
import org.kodejava.hibernate.SessionFactoryHelper;
import org.kodejava.hibernate.model.Label;

import java.util.List;

public class LabelService {
    public List<Label> getLabels(int pageNumber, int pageSize) {
        Session session =
                SessionFactoryHelper.getSessionFactory().getCurrentSession();
        session.beginTransaction();

        Query<Label> query = session.createQuery("from Label", Label.class);

        // Set the first record position and the max number of record to be
        // read. The setFirstResult() tell hibernate from which row the data
        // should be read. In the example if we have pages of 10 records,
        // passing the page number 2 will read 10 records from the 20th row
        // in the selected records.
        query.setFirstResult((pageNumber - 1) * pageSize);
        query.setMaxResults(pageSize);

        List<Label> labels = query.list();
        session.getTransaction().commit();
        return labels;
    }
}

package org.kodejava.hibernate;

import org.kodejava.hibernate.model.Label;
import org.kodejava.hibernate.service.LabelService;

import java.util.List;

public class LimitDemo {
    public static void main(String[] args) {
        LabelService service = new LabelService();

        List<Label> labels = service.getLabels(1, 10);
        for (Label label : labels) {
            System.out.println("Label = " + label);
        }
    }
}

Maven Dependencies

<dependencies>
    <dependency>
        <groupId>org.hibernate</groupId>
        <artifactId>hibernate-core</artifactId>
        <version>5.6.9.Final</version>
    </dependency>
    <dependency>
        <groupId>com.mysql</groupId>
        <artifactId>mysql-connector-j</artifactId>
        <version>8.0.33</version>
    </dependency>
</dependencies>

Maven Central Maven Central

How do I store properties as XML file?

By Wayan in Core API, IO 0 Comment

In the previous example, How do I load properties from XML file? we read properties from XML file. Now it’s the turn on how to store the properties as XML file.

package org.kodejava.io;

import java.io.FileOutputStream;
import java.nio.charset.StandardCharsets;
import java.util.Properties;

public class PropertiesToXml {
    public static void main(String[] args) throws Exception {
        Properties properties = new Properties();
        properties.setProperty("db.type", "mysql");
        properties.setProperty("db.url", "jdbc:mysql://localhost:3306/kodejava");
        properties.setProperty("db.username", "root");
        properties.setProperty("db.password", "");

        FileOutputStream fos = new FileOutputStream("db-config.xml");
        properties.storeToXML(fos, "Database Configuration", StandardCharsets.UTF_8);
    }
}

The saved XML file will look like the properties file below:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE properties SYSTEM "http://java.sun.com/dtd/properties.dtd">
<properties>
    <comment>Database Configuration</comment>
    <entry key="db.type">mysql</entry>
    <entry key="db.password"></entry>
    <entry key="db.username">root</entry>
    <entry key="db.url">jdbc:mysql://localhost:3306/kodejava</entry>
</properties>