How do I convert Set into List?

By Wayan in Core API, Util Package 0 Comment

The code below gives you an example of converting a java.util.Set into a java.util.List. It has simply done by creating a new instance of List and pass the Set as the argument of the constructor.

package org.kodejava.util;

import java.util.*;

public class SetToList {
    public static void main(String[] args) {
        // Create a Set and add some objects into the Set.
        Set<Object> set = new HashSet<>();
        set.add("A");
        set.add(10L);
        set.add(new Date());

        // Convert the Set to a List can be done by passing the Set instance into
        // the constructor of a List implementation class such as ArrayList.
        List<Object> list = new ArrayList<>(set);
        for (Object o : list) {
            System.out.println("Object = " + o);
        }
    }
}

The output of the code snippet are:

Object = A
Object = 10
Object = Mon Oct 04 20:20:26 CST 2021

How do I convert LinkedList to array?

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

import java.util.LinkedList;
import java.util.List;

public class LinkedListToArray {
    public static void main(String[] args) {
        List<String> list = new LinkedList<>();
        list.add("Blue");
        list.add("Green");
        list.add("Purple");
        list.add("Orange");

        // Converting LinkedList to array can be done by calling the toArray()
        // method of the List;
        String[] colors = new String[list.size()];
        list.toArray(colors);

        for (String color : colors) {
            System.out.println("color = " + color);
        }
    }
}

How do I retrieve a list of Hibernate’s persistent objects?

By Wayan in Hibernate 0 Comment

In this example we add the function to read a list of records in our LabelService class. This function will read all Label persistent object from database. You can see the other functions such as saveLabel, getLabel and deleteLabel in the related example section of this example.

package org.kodejava.hibernate.service;

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

import java.util.List;

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

        // We read labels record from database using a simple Hibernate
        // query, Hibernate Query Language (HQL).
        List<Label> labels = session.createQuery("from Label", Label.class)
                .list();
        session.getTransaction().commit();

        return labels;
    }

    public void saveLabel(Label label) {
        // To save an object we first get a session by calling 
        // getCurrentSession() method from the SessionFactoryHelper class. 
        // Next we create a new transaction, save the Label object and 
        // commit it to database,
        Session session = SessionFactoryHelper.getSessionFactory()
                .getCurrentSession();

        session.beginTransaction();
        session.save(label);
        session.getTransaction().commit();
    }
}

package org.kodejava.hibernate;

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

import java.util.Date;
import java.util.List;

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

        // Creates a Label object we are going to store in the database.
        // We set the name, modified by and modified date information.
        Label newLabel = new Label();
        newLabel.setName("PolyGram");
        newLabel.setCreated(new Date());

        // Call the LabelManager saveLabel method.
        service.saveLabel(newLabel);

        List<Label> labels = service.getLabels();
        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 convert Array to Collection?

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

import java.util.Arrays;
import java.util.List;

public class ArrayToListExample {
    public static void main(String[] args) {
        // Creates an array of object, in this case we create an
        // Integer array.
        Integer[] numbers = {1, 1, 2, 3, 5, 8, 13, 21, 34, 55};

        // Convert the created array above to collection, in this
        // example we convert it to a List.
        List<Integer> list = Arrays.asList(numbers);

        // We've got a list of our array here and iterate it.
        for (Integer number : list) {
            System.out.print(number + ", ");
        }
    }
}

How do I convert a collection object into an array?

By Wayan in Core API, Util Package 0 Comment

To convert collection-based object into an array we can use toArray() or toArray(T[] a) method provided by the implementation of Collection interface such as java.util.ArrayList.

package org.kodejava.util;

import java.util.List;
import java.util.ArrayList;

public class CollectionToArrayExample {
    public static void main(String[] args) {
        List<String> words = new ArrayList<>();
        words.add("Kode");
        words.add("Java");
        words.add("-");
        words.add("Learn");
        words.add("Java");
        words.add("by");
        words.add("Examples");

        String[] array = words.toArray(new String[0]);
        for (String word : array) {
            System.out.println(word);
        }
    }
}

Our code snippet result is shown below:

Kode
Java
-
Learn
Java
by
Examples