Java-Buddy

Java example of SSL Server and Client, and how to generate keystore

2016-07-20T09:21:00.001-07:00

Here are examples of Java SSL Server and Client.

JavaSSLServer.java

package javasslserver;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.net.ssl.SSLServerSocketFactory;

/**
 * @web http://java-buddy.blogspot.com/
 */
public class JavaSSLServer {
    
    static final int port = 8000;

    public static void main(String[] args) {
        
        
        SSLServerSocketFactory sslServerSocketFactory = 
                (SSLServerSocketFactory)SSLServerSocketFactory.getDefault();
        
        try {
            ServerSocket sslServerSocket = 
                    sslServerSocketFactory.createServerSocket(port);
            System.out.println("SSL ServerSocket started");
            System.out.println(sslServerSocket.toString());
            
            Socket socket = sslServerSocket.accept();
            System.out.println("ServerSocket accepted");
            
            PrintWriter out = new PrintWriter(socket.getOutputStream(), true);
            try (BufferedReader bufferedReader = 
                    new BufferedReader(
                            new InputStreamReader(socket.getInputStream()))) {
                String line;
                while((line = bufferedReader.readLine()) != null){
                    System.out.println(line);
                    out.println(line);
                }
            }
            System.out.println("Closed");
            
        } catch (IOException ex) {
            Logger.getLogger(JavaSSLServer.class.getName())
                    .log(Level.SEVERE, null, ex);
        }
    }
    
}

JavaSSLClient.java

package javasslclient;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.Socket;
import java.util.Scanner;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.net.ssl.SSLSocketFactory;

/**
 * @web http://java-buddy.blogspot.com/
 */
public class JavaSSLClient {
    
    static final int port = 8000;

    public static void main(String[] args) {
        
        SSLSocketFactory sslSocketFactory = 
                (SSLSocketFactory)SSLSocketFactory.getDefault();
        try {
            Socket socket = sslSocketFactory.createSocket("localhost", port);
            PrintWriter out = new PrintWriter(socket.getOutputStream(), true);
            try (BufferedReader bufferedReader = 
                    new BufferedReader(
                            new InputStreamReader(socket.getInputStream()))) {
                Scanner scanner = new Scanner(System.in);
                while(true){
                    System.out.println("Enter something:");
                    String inputLine = scanner.nextLine();
                    if(inputLine.equals("q")){
                        break;
                    }
                    
                    out.println(inputLine);
                    System.out.println(bufferedReader.readLine());
                }
            }
            
        } catch (IOException ex) {
            Logger.getLogger(JavaSSLClient.class.getName())
                    .log(Level.SEVERE, null, ex);
        }
         
    }
    
}

Without keystore, both the server and client will fail. This video show how to generate keystore using keytool program. Then run server and client with keystore and password.

Type the following command in your command window to create a keystore named examplestore and to generate keys:

$ keytool -genkey -alias signFiles -keystore examplestore

You will be prompted to enter passwords for the key and keystore. The password in this example is "password".

(reference: https://docs.oracle.com/javase/tutorial/security/toolsign/step3.html)

Run SSL server and client by entering the commands:
$ java -jar -Djavax.net.ssl.keyStore=keystore -Djavax.net.ssl.keyStorePassword=password "...JavaSSLServer.jar"
$ java -jar -Djavax.net.ssl.trustStore=keystore -Djavax.net.ssl.trustStorePassword=password "...JavaSSLClient.jar"

Read csv, run in background thread and update JavaFX TableView dynamically

2016-06-16T09:25:00.001-07:00

It's modified version of last example "Read csv file, display in JavaFX TableView", with the job run in background thread. I also add dummy delay to simulate long time operation in background thread.

JavaFXCSVTableView.java

package javafxcsvtableview;

import java.io.BufferedReader;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
import java.util.logging.Level;
import java.util.logging.Logger;
import javafx.application.Application;
import javafx.application.Platform;
import javafx.beans.property.SimpleStringProperty;
import javafx.collections.FXCollections;
import javafx.collections.ObservableList;
import javafx.scene.Group;
import javafx.scene.Scene;
import javafx.scene.control.TableColumn;
import javafx.scene.control.TableView;
import javafx.scene.control.cell.PropertyValueFactory;
import javafx.scene.layout.VBox;
import javafx.stage.Stage;

/**
 * @web http://java-buddy.blogspot.com/
 */
public class JavaFXCSVTableView extends Application {

    public class Record {
        //Assume each record have 6 elements, all String

        private SimpleStringProperty f1, f2, f3, f4, f5, f6;

        public String getF1() {
            return f1.get();
        }

        public String getF2() {
            return f2.get();
        }

        public String getF3() {
            return f3.get();
        }

        public String getF4() {
            return f4.get();
        }

        public String getF5() {
            return f5.get();
        }

        public String getF6() {
            return f6.get();
        }

        Record(String f1, String f2, String f3, String f4,
                String f5, String f6) {
            this.f1 = new SimpleStringProperty(f1);
            this.f2 = new SimpleStringProperty(f2);
            this.f3 = new SimpleStringProperty(f3);
            this.f4 = new SimpleStringProperty(f4);
            this.f5 = new SimpleStringProperty(f5);
            this.f6 = new SimpleStringProperty(f6);
        }

    }

    private final TableView<Record> tableView = new TableView<>();

    private final ObservableList<Record> dataList
            = FXCollections.observableArrayList();

    @Override
    public void start(Stage primaryStage) {
        primaryStage.setTitle("java-buddy.blogspot.com");

        Group root = new Group();

        TableColumn columnF1 = new TableColumn("f1");
        columnF1.setCellValueFactory(
                new PropertyValueFactory<>("f1"));

        TableColumn columnF2 = new TableColumn("f2");
        columnF2.setCellValueFactory(
                new PropertyValueFactory<>("f2"));

        TableColumn columnF3 = new TableColumn("f3");
        columnF3.setCellValueFactory(
                new PropertyValueFactory<>("f3"));

        TableColumn columnF4 = new TableColumn("f4");
        columnF4.setCellValueFactory(
                new PropertyValueFactory<>("f4"));

        TableColumn columnF5 = new TableColumn("f5");
        columnF5.setCellValueFactory(
                new PropertyValueFactory<>("f5"));

        TableColumn columnF6 = new TableColumn("f6");
        columnF6.setCellValueFactory(
                new PropertyValueFactory<>("f6"));

        tableView.setItems(dataList);
        tableView.getColumns().addAll(
                columnF1, columnF2, columnF3, columnF4, columnF5, columnF6);

        VBox vBox = new VBox();
        vBox.setSpacing(10);
        vBox.getChildren().add(tableView);

        root.getChildren().add(vBox);

        primaryStage.setScene(new Scene(root, 700, 250));
        primaryStage.show();

        //readCSV();
        
        //run in background thread
        new Thread() {
            
            @Override
            public void run() {
                readCSV();
            };
            
        }.start();
        
    }

    private void readCSV() {
        
        System.out.println("Platform.isFxApplicationThread(): "
                        + Platform.isFxApplicationThread());

        String CsvFile = "/home/buddy/test/test.csv";
        String FieldDelimiter = ",";

        BufferedReader br;

        try {
            br = new BufferedReader(new FileReader(CsvFile));

            String line;
            while ((line = br.readLine()) != null) {
                String[] fields = line.split(FieldDelimiter, -1);

                Record record = new Record(fields[0], fields[1], fields[2],
                        fields[3], fields[4], fields[5]);
                dataList.add(record);

                //Add delay to simulate long time operation
                try {
                    Thread.sleep(2000);
                } catch (InterruptedException ex) {
                    Logger.getLogger(JavaFXCSVTableView.class.getName())
                            .log(Level.SEVERE, null, ex);
                }
            }

        } catch (FileNotFoundException ex) {
            Logger.getLogger(JavaFXCSVTableView.class.getName())
                    .log(Level.SEVERE, null, ex);
        } catch (IOException ex) {
            Logger.getLogger(JavaFXCSVTableView.class.getName())
                    .log(Level.SEVERE, null, ex);
        }

    }

    public static void main(String[] args) {
        launch(args);
    }

}

Read csv file, display in JavaFX TableView

2016-06-16T08:52:00.000-07:00

Java example read csv file and display the content in JavaFX TableView.

To know how to prepare the csv file, and simple read csv file, refer to last post.

JavaFXCSVTableView.java

package javafxcsvtableview;

import java.io.BufferedReader;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
import java.util.logging.Level;
import java.util.logging.Logger;
import javafx.application.Application;
import javafx.beans.property.SimpleStringProperty;
import javafx.collections.FXCollections;
import javafx.collections.ObservableList;
import javafx.scene.Group;
import javafx.scene.Scene;
import javafx.scene.control.TableColumn;
import javafx.scene.control.TableView;
import javafx.scene.control.cell.PropertyValueFactory;
import javafx.scene.layout.VBox;
import javafx.stage.Stage;

/**
 * @web http://java-buddy.blogspot.com/
 */
public class JavaFXCSVTableView extends Application {

    public class Record {
        //Assume each record have 6 elements, all String

        private SimpleStringProperty f1, f2, f3, f4, f5, f6;

        public String getF1() {
            return f1.get();
        }

        public String getF2() {
            return f2.get();
        }

        public String getF3() {
            return f3.get();
        }

        public String getF4() {
            return f4.get();
        }

        public String getF5() {
            return f5.get();
        }

        public String getF6() {
            return f6.get();
        }

        Record(String f1, String f2, String f3, String f4,
                String f5, String f6) {
            this.f1 = new SimpleStringProperty(f1);
            this.f2 = new SimpleStringProperty(f2);
            this.f3 = new SimpleStringProperty(f3);
            this.f4 = new SimpleStringProperty(f4);
            this.f5 = new SimpleStringProperty(f5);
            this.f6 = new SimpleStringProperty(f6);
        }

    }

    private final TableView<Record> tableView = new TableView<>();

    private final ObservableList<Record> dataList
            = FXCollections.observableArrayList();

    @Override
    public void start(Stage primaryStage) {
        primaryStage.setTitle("java-buddy.blogspot.com");

        Group root = new Group();

        TableColumn columnF1 = new TableColumn("f1");
        columnF1.setCellValueFactory(
                new PropertyValueFactory<>("f1"));

        TableColumn columnF2 = new TableColumn("f2");
        columnF2.setCellValueFactory(
                new PropertyValueFactory<>("f2"));

        TableColumn columnF3 = new TableColumn("f3");
        columnF3.setCellValueFactory(
                new PropertyValueFactory<>("f3"));

        TableColumn columnF4 = new TableColumn("f4");
        columnF4.setCellValueFactory(
                new PropertyValueFactory<>("f4"));

        TableColumn columnF5 = new TableColumn("f5");
        columnF5.setCellValueFactory(
                new PropertyValueFactory<>("f5"));

        TableColumn columnF6 = new TableColumn("f6");
        columnF6.setCellValueFactory(
                new PropertyValueFactory<>("f6"));

        tableView.setItems(dataList);
        tableView.getColumns().addAll(
                columnF1, columnF2, columnF3, columnF4, columnF5, columnF6);

        VBox vBox = new VBox();
        vBox.setSpacing(10);
        vBox.getChildren().add(tableView);

        root.getChildren().add(vBox);

        primaryStage.setScene(new Scene(root, 700, 250));
        primaryStage.show();

        readCSV();
    }

    private void readCSV() {

        String CsvFile = "/home/buddy/test/test.csv";
        String FieldDelimiter = ",";

        BufferedReader br;

        try {
            br = new BufferedReader(new FileReader(CsvFile));

            String line;
            while ((line = br.readLine()) != null) {
                String[] fields = line.split(FieldDelimiter, -1);

                Record record = new Record(fields[0], fields[1], fields[2],
                        fields[3], fields[4], fields[5]);
                dataList.add(record);

            }

        } catch (FileNotFoundException ex) {
            Logger.getLogger(JavaFXCSVTableView.class.getName())
                    .log(Level.SEVERE, null, ex);
        } catch (IOException ex) {
            Logger.getLogger(JavaFXCSVTableView.class.getName())
                    .log(Level.SEVERE, null, ex);
        }

    }

    public static void main(String[] args) {
        launch(args);
    }

}

Next post show how to do the job in background.

Java to read csv file

2016-06-15T10:03:00.002-07:00

This example show how to read csv file using Java.

Prepare:
- Create a spreadsheet:

- Export as csv file:

- The exported csv file in text format:

Using java to read the csv file and print the content:

package javareadcsv;

import java.io.BufferedReader;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
import java.util.logging.Level;
import java.util.logging.Logger;

/**
 * @web http://java-buddy.blogspot.com/
 */
public class JavaReadCSV {
    
    static String CsvFile = "/home/buddy/test/test.csv";
    static String FieldDelimiter = ",";

    public static void main(String[] args) throws IOException {
        BufferedReader br;
        
        try {
            br = new BufferedReader(new FileReader(CsvFile));
            
            String line;
            while ((line = br.readLine()) != null) {
                String[] fields = line.split(FieldDelimiter, -1);
                System.out.print(fields.length + "-");
                for(String s : fields){
                    System.out.print(s);
                    System.out.print(":");
                }
                System.out.println();
            }
            
        } catch (FileNotFoundException ex) {
            Logger.getLogger(JavaReadCSV.class.getName())
                    .log(Level.SEVERE, null, ex);
        }
        
    }
    
}

To display the content with JavaFX TableView, read next post.

Java example using Supplier to get input from Scanner

2016-06-07T16:56:00.001-07:00

Java example using java.util.function.Supplier to get input from java.util.Scanner.

JavaSupplier.java

package javasupplier;

import java.util.Scanner;
import java.util.function.Supplier;
import java.util.stream.Stream;

public class JavaSupplier {

    public static void main(String[] args) {
        Supplier<String> msg  = ()-> "http://java-buddy.blogspot.com/";
        System.out.println(msg.get());
        System.out.println();
        
        Scanner scanner = new Scanner(System.in);
        Supplier<String> scannerNext = () -> scanner.next();
        System.out.println("Enter something, 'q' to quit");
        
        Stream.generate(scannerNext)
                .map(s -> {
                    System.out.println(s);
                    return s;
                })
                .allMatch(s -> !"q".equals(s));
    }
    
}

Get my MAC address using NetworkInterface

2016-04-17T04:59:00.000-07:00

Java example to get MAC address using NetworkInterface:

package javamyip;

import java.net.InetAddress;
import java.net.NetworkInterface;
import java.net.SocketException;
import java.util.Collections;
import java.util.Enumeration;
import java.util.logging.Level;
import java.util.logging.Logger;

/**
 * @web http://java-buddy.blogspot.com/
 */
public class JavaMyIP {

    public static void main(String[] args) {
        displayMyIP();
    }
    
    static void displayMyIP(){
        Enumeration<NetworkInterface> nets;
        try {
            nets = NetworkInterface.getNetworkInterfaces();
            for (NetworkInterface netint : Collections.list(nets)){
                System.out.printf(netint.getDisplayName() +"\n");
                Enumeration<InetAddress> inetAddresses = netint.getInetAddresses();
                for (InetAddress inetAddress : Collections.list(inetAddresses)) {
                    System.out.printf("InetAddress: %s\n", inetAddress);
                }
                
                byte[] mac = netint.getHardwareAddress();
                if(mac != null){
                    StringBuilder macAddr = new StringBuilder();
                    for (int i = 0; i < mac.length; i++) {
                        macAddr.append(String.format("%02X%s", mac[i], (i < mac.length - 1) ? ":" : "")); 
                    }
                    System.out.printf("Hardware address (MAC): [%s]\n", macAddr.toString());
                }
                
                System.out.printf("\n");
            }
        } catch (SocketException ex) {
            Logger.getLogger(JavaMyIP.class.getName()).log(Level.SEVERE, null, ex);
        }
    }
}

List my IP (inetAddress)

2016-04-15T18:36:00.001-07:00

Java example to list Network Interface Addresses and IP:

package javamyip;

import java.net.InetAddress;
import java.net.NetworkInterface;
import java.net.SocketException;
import java.util.Collections;
import java.util.Enumeration;
import java.util.logging.Level;
import java.util.logging.Logger;

/**
 * @web http://java-buddy.blogspot.com/
 */
public class JavaMyIP {

    public static void main(String[] args) {
        displayMyIP();
    }
    
    static void displayMyIP(){
        Enumeration<NetworkInterface> nets;
        try {
            nets = NetworkInterface.getNetworkInterfaces();
            for (NetworkInterface netint : Collections.list(nets)){
                System.out.printf(netint.getDisplayName() +"\n");
                Enumeration<InetAddress> inetAddresses = netint.getInetAddresses();
                for (InetAddress inetAddress : Collections.list(inetAddresses)) {
                    System.out.printf("InetAddress: %s\n", inetAddress);
                }
                System.out.printf("\n");
            }
        } catch (SocketException ex) {
            Logger.getLogger(JavaMyIP.class.getName()).log(Level.SEVERE, null, ex);
        }
    }
}

Can use functional operations in Java 8 (auto suggested by Netbeans):

package javamyip;

import java.net.InetAddress;
import java.net.NetworkInterface;
import java.net.SocketException;
import java.util.Collections;
import java.util.Enumeration;
import java.util.logging.Level;
import java.util.logging.Logger;

/**
 * @web http://java-buddy.blogspot.com/
 */
public class JavaMyIP {

    public static void main(String[] args) {
        displayMyIP();
    }
    
    static void displayMyIP(){
        Enumeration<NetworkInterface> nets;
        try {
            nets = NetworkInterface.getNetworkInterfaces();
            Collections.list(nets).stream().map((netint) -> {
                System.out.printf(netint.getDisplayName() +"\n");
                return netint;
            }).map((netint) -> netint.getInetAddresses()).map((inetAddresses) -> {
                Collections.list(inetAddresses).stream().forEach((inetAddress) -> {
                    System.out.printf("InetAddress: %s\n", inetAddress);
                });
                return inetAddresses;
            }).forEach((_item) -> {
                System.out.printf("\n");
            });
        } catch (SocketException ex) {
            Logger.getLogger(JavaMyIP.class.getName()).log(Level.SEVERE, null, ex);
        }
    }
}

Create ServerSocket with automatically allocated port

2016-04-13T20:08:00.001-07:00

Create ServerSocket by calling constructor ServerSocket(int port) with port = 0, the port number is automatically allocated, typically from an ephemeral port range. This port number can then be retrieved by calling getLocalPort.

Example:

package javaechoserver;

import java.io.IOException;
import java.net.ServerSocket;
import java.util.logging.Level;
import java.util.logging.Logger;

/**
 *
 * @web http://java-buddy.blogspot.com/
 */
public class JavaEchoServer {

    public static void main(String[] args) {
        ServerSocket serverSocket = null;
        try {
            //Get a available port by passing 0 
            serverSocket = new ServerSocket(0);
            int port = serverSocket.getLocalPort();
            System.out.println("Port : " + port);
            
        } catch (IOException ex) {
            Logger.getLogger(JavaEchoServer.class.getName())
                    .log(Level.SEVERE, null, ex);
        } finally {
            if (serverSocket != null){
                try {
                    serverSocket.close();
                } catch (IOException ex) {
                    Logger.getLogger(JavaEchoServer.class.getName())
                            .log(Level.SEVERE, null, ex);
                }
            }
        }
    }
    
}

Mastering Concurrency Programming with Java 8

2016-03-25T04:57:00.002-07:00

Master the principles and techniques of multithreaded programming with the Java 8 Concurrency API

Mastering Concurrency Programming with Java 8

About This Book

Implement concurrent applications using the Java 8 Concurrency API and its new components
Improve the performance of your applications or process more data at the same time, taking advantage of all of your resources.
Construct real-world examples related to machine learning, data mining, image processing, and client/server environments

Who This Book Is For
If you are a competent Java developer with a good understanding of concurrency but have no knowledge of how to effectively implement concurrent programs or use streams to make processes more efficient, then this book is for you.

What You Will Learn

Design concurrent applications by converting a sequential algorithm into a concurrent one
Discover how to avoid all the possible problems you can get in concurrent algorithms
Use the Executor framework to manage concurrent tasks without creating threads
Extend and modify Executors to adapt their behavior to your needs
Solve problems using the divide and conquer technique and the Fork/Join framework
Process massive data sets with parallel streams and Map/Reduce implementation
Control data-race conditions using concurrent data structures and synchronization mechanisms
Test and monitor concurrent applications

In Detail
Concurrency programming allows several large tasks to be divided into smaller sub-tasks, which are further processed as individual tasks that run in parallel. All the sub-tasks are combined together once the required results are achieved; they are then merged to get the final output. The whole process is very complex. This process goes from the design of concurrent algorithms to the testing phase where concurrent applications need extra attention. Java includes a comprehensive API with a lot of ready-to-use components to implement powerful concurrency applications in an easy way, but with a high flexibility to adapt these components to your needs.

The book starts with a full description of design principles of concurrent applications and how to parallelize a sequential algorithm. We'll show you how to use all the components of the Java Concurrency API from basics to the most advanced techniques to implement them in powerful concurrency applications in Java.

You will be using real-world examples of complex algorithms related to machine learning, data mining, natural language processing, image processing in client / server environments. Next, you will learn how to use the most important components of the Java 8 Concurrency API: the Executor framework to execute multiple tasks in your applications, the phaser class to implement concurrent tasks divided into phases, and the Fork/Join framework to implement concurrent tasks that can be split into smaller problems (using the divide and conquer technique). Toward the end, we will cover the new inclusions in Java 8 API, the Map and Reduce model, and the Map and Collect model. The book will also teach you about the data structures and synchronization utilities to avoid data-race conditions and other critical problems. Finally, the book ends with a detailed description of the tools and techniques that you can use to test a Java concurrent application.

Style and approach
A complete guide implementing real-world examples with algorithms related to machine learning, data mining, and natural language processing in client/server environments. All the examples are explained in a step-by-step approach.

JavaFX example: open new Window and exit all when primary window close

2016-03-14T17:08:00.001-07:00

JavaFX example to open new Window, and exit all when primary window close.

package javafxwindow;

import javafx.application.Application;
import javafx.application.Platform;
import javafx.event.ActionEvent;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.control.Label;
import javafx.scene.layout.StackPane;
import javafx.stage.Stage;

/**
 *
 * @web http://java-buddy.blogspot.com/
 */
public class JavaFXWindow extends Application {
    
    @Override
    public void start(Stage primaryStage) {
        Button btn = new Button();
        btn.setText("Open a New Window");
        btn.setOnAction((ActionEvent event) -> {
            Label secondLabel = new Label("Hello");
            
            StackPane secondaryLayout = new StackPane();
            secondaryLayout.getChildren().add(secondLabel);
            
            Scene secondScene = new Scene(secondaryLayout, 200, 100);
            
            Stage secondStage = new Stage();
            secondStage.setTitle("New Stage");
            secondStage.setScene(secondScene);
            
            secondStage.show();

        });
         
        StackPane root = new StackPane();
        root.getChildren().add(btn);
         
        Scene scene = new Scene(root, 300, 250);
         
        primaryStage.setTitle("java-buddy.blogspot.com");
        primaryStage.setScene(scene);
        primaryStage.show();
        
        primaryStage.setOnCloseRequest(e -> Platform.exit());

    }

    public static void main(String[] args) {
        launch(args);
    }
    
}

Read from Internet using URLConnection and BufferedReader

2016-03-06T17:16:00.002-08:00

Java example to read from Internet using URLConnection and BufferedReader. Thanks for Tomtom's comment in my last post "Read from Internet using URLConnection and ReadableByteChannel".

package javaurlconnection;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLConnection;
import java.util.logging.Level;
import java.util.logging.Logger;

/**
 *
 * @web http://java-buddy.blogspot.com/
 */
public class JavaURLConnection {

    public static void main(String[] args) {
        try {
            URL url = new URL("http://java-buddy.blogspot.com");
            URLConnection urlConnection = url.openConnection();
            
            /*
            InputStream inputStream = urlConnection.getInputStream();
            try (ReadableByteChannel readableByteChannel = Channels.newChannel(inputStream)) {
                ByteBuffer buffer = ByteBuffer.allocate(1024);
 
                while (readableByteChannel.read(buffer) > 0)
                {
                    String bufferString = new String(buffer.array());
                    System.out.println(bufferString);
                    buffer.clear();
                }
            }
            */
            
            //using BufferedReader
            InputStream inputStream = urlConnection.getInputStream();
            InputStreamReader inputStreamReader = 
                    new InputStreamReader(inputStream);
            BufferedReader buffReader = new BufferedReader(inputStreamReader);
            String line;
            while ((line = buffReader.readLine()) != null) {
                System.out.println(line);
            }
            
        } catch (MalformedURLException ex) {
            Logger.getLogger(JavaURLConnection.class.getName()).log(Level.SEVERE, null, ex);
        } catch (IOException ex) {
            Logger.getLogger(JavaURLConnection.class.getName()).log(Level.SEVERE, null, ex);
        }
    }
    
}

Read from Internet using URLConnection and ReadableByteChannel

2016-03-03T12:23:00.001-08:00

Java example to read from Internet, "http://java-buddy.blogspot.com", using URLConnection and ReadableByteChannel.

Example:

package javaurlconnection;

import java.io.IOException;
import java.io.InputStream;
import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLConnection;
import java.nio.ByteBuffer;
import java.nio.channels.Channels;
import java.nio.channels.ReadableByteChannel;
import java.util.logging.Level;
import java.util.logging.Logger;

/**
 *
 * @web http://java-buddy.blogspot.com/
 */
public class JavaURLConnection {

    public static void main(String[] args) {
        try {
            URL url = new URL("http://java-buddy.blogspot.com");
            URLConnection urlConnection = url.openConnection();
            InputStream inputStream = urlConnection.getInputStream();
            try (ReadableByteChannel readableByteChannel = Channels.newChannel(inputStream)) {
                ByteBuffer buffer = ByteBuffer.allocate(1024);

                while (readableByteChannel.read(buffer) > 0)
                {
                    String bufferString = new String(buffer.array());
                    System.out.println(bufferString);
                    buffer.clear();
                }
            }
        } catch (MalformedURLException ex) {
            Logger.getLogger(JavaURLConnection.class.getName()).log(Level.SEVERE, null, ex);
        } catch (IOException ex) {
            Logger.getLogger(JavaURLConnection.class.getName()).log(Level.SEVERE, null, ex);
        }
    }
    
}

Related:
- Read from Internet using URLConnection and BufferedReader (Thanks Tomtom comment)

Get IP address of Website using InetAddress

2016-03-01T15:37:00.000-08:00

Java example to get IP address of Website using InetAddress:

package javainetaddress;

import java.net.InetAddress;
import java.net.UnknownHostException;
import java.util.logging.Level;
import java.util.logging.Logger;

/**
 *
 * @web http://java-buddy.blogspot.com/
 */
public class JavaInetAddress {

    public static void main(String[] args) {
        try {
            InetAddress inetAddress = InetAddress.getByName("www.google.com");
            System.out.println(inetAddress);
            System.out.println(inetAddress.getHostName());
            System.out.println(inetAddress.getHostAddress());
        } catch (UnknownHostException ex) {
            Logger.getLogger(JavaInetAddress.class.getName()).log(Level.SEVERE, null, ex);
        }
    }
    
}

JavaFX example to capture screen/GUI nodes

2016-01-09T08:45:00.000-08:00

JavaFX example to capture screen/GUI nodes:

package javafxcapturescreen;

import java.io.File;
import java.io.IOException;
import java.util.logging.Level;
import java.util.logging.Logger;
import javafx.application.Application;
import javafx.embed.swing.SwingFXUtils;
import javafx.event.ActionEvent;
import javafx.scene.Scene;
import javafx.scene.SnapshotParameters;
import javafx.scene.control.Button;
import javafx.scene.image.WritableImage;
import javafx.scene.layout.StackPane;
import javafx.scene.layout.VBox;
import javafx.stage.Stage;
import javax.imageio.ImageIO;

/**
 *
 * @web http://java-buddy.blogspot.com/
 */
public class JavaFXCaptureScreen extends Application {
    
    @Override
    public void start(Stage primaryStage) {
        StackPane root = new StackPane();
        Scene scene = new Scene(root, 300, 250);
        
        Button btnCaptureScene = new Button();
        btnCaptureScene.setText("Capture scene");
        btnCaptureScene.setOnAction((ActionEvent event) -> {
            
            WritableImage writableImage = scene.snapshot(null);
            File file = new File("capturedScene.png");
            try {
                ImageIO.write(SwingFXUtils.fromFXImage(writableImage, null), "png", file);
                System.out.println("Captured: " + file.getAbsolutePath());
            } catch (IOException ex) {
                Logger.getLogger(JavaFXCaptureScreen.class.getName()).log(Level.SEVERE, null, ex);
            }
        });
        
        Button btnCaptureRoot = new Button();
        btnCaptureRoot.setText("Capture root");
        btnCaptureRoot.setOnAction((ActionEvent event) -> {
            WritableImage writableImage = root.snapshot(new SnapshotParameters(), null);

            File file = new File("capturedRoot.png");
            try {
                ImageIO.write(SwingFXUtils.fromFXImage(writableImage, null), "png", file);
                System.out.println("Captured: " + file.getAbsolutePath());
            } catch (IOException ex) {
                Logger.getLogger(JavaFXCaptureScreen.class.getName()).log(Level.SEVERE, null, ex);
            }
        });
        
        VBox vBox = new VBox();
        vBox.getChildren().addAll(btnCaptureScene, btnCaptureRoot);
        root.getChildren().add(vBox);
        
        primaryStage.setTitle("java-buddy.blogspot.com");
        primaryStage.setScene(scene);
        primaryStage.show();
    }

    public static void main(String[] args) {
        launch(args);
    }
    
}

capturedScene.png

capturedRoot.png

Capture screen using java.awt.Robot

2016-01-07T08:29:00.002-08:00

Java example to capture screen using java.awt.Robot:

package javarobotcapturescreen;

import java.awt.AWTException;
import java.awt.Dimension;
import java.awt.Rectangle;
import java.awt.Robot;
import java.awt.Toolkit;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.imageio.ImageIO;

/**
 *
 * @web http://java-buddy.blogspot.com/
 */
public class JavaRobotCaptureScreen {

    public static void main(String[] args) {
        try {
            Robot robot = new Robot();
            
            Toolkit myToolkit = Toolkit.getDefaultToolkit();
            Dimension screenSize = myToolkit.getScreenSize();
            
            Rectangle screen = new Rectangle(screenSize);
            
            BufferedImage screenFullImage = robot.createScreenCapture(screen);
            ImageIO.write(screenFullImage, "jpg", new File("screen.jpg"));
            
        } catch (AWTException | IOException ex) {
            Logger.getLogger(JavaRobotCaptureScreen.class.getName()).log(Level.SEVERE, null, ex);
        }
    }
    
}

captured screen:

Get screen size and resolution, with java.awt.Toolkit

2016-01-07T02:25:00.001-08:00

Java example to get screen size and resolution, with java.awt.Toolkit:

package javagetscreensize;

import java.awt.Dimension;
import java.awt.Toolkit;

/**
 *
 * @web http://java-buddy.blogspot.com/
 */
public class JavaGetScreenSize {

    public static void main(String[] args) {
        Toolkit myToolkit = Toolkit.getDefaultToolkit();
        Dimension screenSize = myToolkit.getScreenSize();
        int screenResolution = myToolkit.getScreenResolution();
        System.out.println("Screen size = " + screenSize.width + " x " + screenSize.height);
        System.out.println("Screen Resolution: " + screenResolution + " dots-per-inch");
    }
    
}

Java Everywhere: Write Once run Anywhere with DukeScript

2016-01-07T01:07:00.000-08:00

Java Everywhere: Write Once run Anywhere with DukeScript

Do you want to write Java apps that run on mobile phones, tablets as well as your desktop computer? In this book you'll learn how to design and develop apps and upload them to Google Play and Apples App Store. The technology we'll use for that is DukeScript, a new framework for single-source cross-platform development in Java.

Files.lines() read text file returned by JavaFX FileChooser

2015-12-28T07:19:00.000-08:00

Example show how to read all lines from a file returned by JavaFX FileChooser, using Files.lines().

package javafxreadtextfile;

import java.io.File;
import java.io.IOException;
import java.nio.file.Files;
import java.util.logging.Level;
import java.util.logging.Logger;
import javafx.application.Application;
import javafx.event.ActionEvent;
import javafx.event.EventHandler;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.layout.VBox;
import javafx.stage.FileChooser;
import javafx.stage.Stage;

/**
 *
 * @web http://java-buddy.blogspot.com/
 */
public class JavaFXReadTextFile extends Application {

    @Override
    public void start(Stage primaryStage) {
        Button btnLoad = new Button("Load");
        btnLoad.setOnAction(btnLoadEventListener);

        VBox rootBox = new VBox();
        rootBox.getChildren().add(btnLoad);
         
        Scene scene = new Scene(rootBox, 300, 300);
         
        primaryStage.setTitle("java-buddy.blogspot.com");
        primaryStage.setScene(scene);
        primaryStage.show();
    }
    
    EventHandler<ActionEvent> btnLoadEventListener
    = (ActionEvent event) -> {
        FileChooser fileChooser = new FileChooser();
        fileChooser.getExtensionFilters()
            .addAll(
                new FileChooser.ExtensionFilter("TXT files (*.TXT)", "*.TXT"),
                new FileChooser.ExtensionFilter("txt files (*.txt)", "*.txt"));
        
        File file = fileChooser.showOpenDialog(null);
        if (file != null) {
            try {
                Files.lines(file.toPath()).forEach(System.out::println);
            } catch (IOException ex) {
                Logger.getLogger(JavaFXReadTextFile.class.getName())
                        .log(Level.SEVERE, null, ex);
            }
        }
    };

    public static void main(String[] args) {
        launch(args);
    }
    
}

JavaFX FileChooser to open image file, and display on ImageView, run on Ubuntu GNOME 15.10/NetBeans 8.1

2015-12-06T12:10:00.001-08:00

Re-test "Use JavaFX FileChooser to open image file, and display on ImageView" on Ubuntu GNOME 15.10/NetBeans 8.1.

package javafxpixel;

import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import java.util.logging.Level;
import java.util.logging.Logger;
import javafx.application.Application;
import javafx.embed.swing.SwingFXUtils;
import javafx.event.ActionEvent;
import javafx.event.EventHandler;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.image.Image;
import javafx.scene.image.ImageView;
import javafx.scene.layout.VBox;
import javafx.stage.FileChooser;
import javafx.stage.Stage;
import javax.imageio.ImageIO;

/**
 * @web http://java-buddy.blogspot.com/
 */
public class JavaFxPixel extends Application {
    
    ImageView myImageView;
    
    @Override
    public void start(Stage primaryStage) {
        Button btnLoad = new Button("Load");
        btnLoad.setOnAction(btnLoadEventListener);
         
        myImageView = new ImageView();        
         
        VBox rootBox = new VBox();
        rootBox.getChildren().addAll(btnLoad, myImageView);
         
        Scene scene = new Scene(rootBox, 300, 300);
         
        primaryStage.setTitle("java-buddy.blogspot.com");
        primaryStage.setScene(scene);
        primaryStage.show();
    }

    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {
        launch(args);
    }
    
    EventHandler<ActionEvent> btnLoadEventListener
    = new EventHandler<ActionEvent>(){
 
        @Override
        public void handle(ActionEvent t) {
            FileChooser fileChooser = new FileChooser();
             
            //Set extension filter
            FileChooser.ExtensionFilter extFilterJPG = 
                    new FileChooser.ExtensionFilter("JPG files (*.JPG)", "*.JPG");
            FileChooser.ExtensionFilter extFilterjpg = 
                    new FileChooser.ExtensionFilter("jpg files (*.jpg)", "*.jpg");
            FileChooser.ExtensionFilter extFilterPNG = 
                    new FileChooser.ExtensionFilter("PNG files (*.PNG)", "*.PNG");
            FileChooser.ExtensionFilter extFilterpng = 
                    new FileChooser.ExtensionFilter("png files (*.png)", "*.png");
            fileChooser.getExtensionFilters()
                    .addAll(extFilterJPG, extFilterjpg, extFilterPNG, extFilterpng);

            //Show open file dialog
            File file = fileChooser.showOpenDialog(null);
            
            try {
                BufferedImage bufferedImage = ImageIO.read(file);
                Image image = SwingFXUtils.toFXImage(bufferedImage, null);
                myImageView.setImage(image);
            } catch (IOException ex) {
                Logger.getLogger(JavaFxPixel.class.getName()).log(Level.SEVERE, null, ex);
            }
        }
    };
}

Query InterNIC server's whois

2015-11-11T12:17:00.000-08:00

Last example show Java example using WhoisClient class to query whois. Alternatively, we can query InterNIC server's whois without WhoisClient class.

package javawhois;

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.Socket;
import java.util.logging.Level;
import java.util.logging.Logger;

/**
 * @web http://java-buddy.blogspot.com/
 */
public class JavaWhoIs {
    
    private final static String WHO ="google.com";

    private final static String WHOIS_HOST = "whois.internic.net";
    private final static int WHOIS_PORT = 43;

    public static void main(String[] args) {
        int c;
        Socket socket = null; 

        String query = "=" + WHO + "\r\n";
        byte buf[] = query.getBytes();
        
        try {
            socket = new Socket(WHOIS_HOST, WHOIS_PORT);
            InputStream in = socket.getInputStream();
            OutputStream out = socket.getOutputStream(); 

            out.write(buf); 
            out.flush();
            while ((c = in.read()) != -1) { 
                System.out.print((char) c); 
            } 
            System.out.print("\nDone\n");
        } catch (IOException ex) {
            Logger.getLogger(JavaWhoIs.class.getName()).log(Level.SEVERE, null, ex);
            System.out.print(ex.getMessage());
        } finally {
            if(socket != null){
                try {
                    socket.close();
                } catch (IOException ex) {
                    Logger.getLogger(JavaWhoIs.class.getName()).log(Level.SEVERE, null, ex);
                }
            }
        }
    }
    
}

Java example using WhoisClient class

2015-11-08T21:48:00.002-08:00

The WhoisClient class implements the client side of the Internet Whois Protocol defined in RFC 954. To query a host you create a WhoisClient instance, connect to the host, query the host, and finally disconnect from the host. If the whois service you want to query is on a non-standard port, connect to the host at that port.
~ org.apache.commons.net.whois.WhoisClient

Example:

package javawhoisclient;

import java.io.IOException;
import org.apache.commons.net.whois.WhoisClient;

/**
 *
 * @web http://java-buddy.blogspot.com/
 */
public class JavaWhoisClient {

    public static void main(String[] args) {
        WhoisClient whois;

        whois = new WhoisClient();

        try {
            whois.connect(WhoisClient.DEFAULT_HOST);
            System.out.println(whois.query("=google.com"));
            whois.disconnect();
        } catch (IOException e) {
            System.err.println("Error I/O exception: " + e.getMessage());
            return;
        }
    }

}

To use WhoisClient class in your program, you have to include library commons-net-3.3 in your code, it can be download here: https://commons.apache.org/proper/commons-net/index.html

This video show how to download and add library commons-net-3.3 to NetBeans IDE.

Next:
- query InterNIC server's whois without WhoisClient class.

Install Netbeans 8.1 0n Ubuntu 15.10

2015-11-08T02:46:00.001-08:00

Netbeans IDE 8.1 just released.

This video show how to download and install Netbeans IDE 8.1 on Ubuntu-GNOME 15.10

To install Ubuntu 8.1 on Ubuntu:

- Visit https://netbeans.org/ to download installer-file.

- chmod +x <installer-file-name>.

- run it with command:

./<installer-file-name> to run the installer.

The only special is to select correct path to JDK, 1:40 in the above video.

My JDK was installed with ppa:webupd8team, it's on "/usr/lib/jvm/java-8-oracle".

If you missed the setting JDK path, you still run edit netbeans.conf, to specify netbeans_jdkhome, or run netbeans with --jdkhome option. (ref: http://wiki.netbeans.org/FaqRunningOnJre)

netbeans.conf to set netbeans_jdkhome:

run netbeans with --jdkhome option:

JavaOne Keynote Highlights 10-25-2015

2015-11-05T21:35:00.000-08:00

JavaOne Keynote Highlights 10-25-2015 from Oracle

Java I/O, NIO and NIO.2

2015-11-05T20:19:00.003-08:00

Java I/O, NIO and NIO.2

Java I/O, NIO, and NIO.2 is a power-packed book that accelerates your mastery of Java's various I/O APIs. In this book, you'll learn about classic I/O APIs (File, RandomAccessFile, the stream classes and related types, and the reader/writer classes). Next, you'll learn about NIO's buffer, channel, selector, regular expression, charset, and formatter APIs. Finally, you'll discover NIO.2's offerings in terms of an improved file system interface, asynchronous I/O, and the completion of socket channel functionality.

After reading and using thi book, you'll gain the accelerated knowledge and skill level to really build applications with efficient data access, especially for today's cloud computing streaming data needs.

What you’ll learn

How to set permissions and more with the classic File class
How to build a flat file database with RandomAccessFile
Get to know the byte array, file, filter, and other kinds of streams
Master serialization and externalization
Discover character streams and their associated writers/readers
Tour the buffer APIs
Work with channels to transfer buffers to and from I/O services
Find out about selectors and readiness selection
Master regular expressions
Discover charsets and their association with Java's String< class
Take advantage of the formatter API to create formatted output
How to customize the formatter API
Explore the improved file system interface
Discover asynchronous I/O and its association with futures and completion handlers
Encounter socket channel improvements, including multicasting

Who this book is for
This book is for those experienced with Java, beyond the fundamentals.

Table of Contents
Part 1: Getting Started with I/O
Chapter 1: I/O Basics and APIs
Part 2: Classic I/O APIs
Chapter 2: File
Chapter 3: RandomAccessFile
Chapter 4: Streams
Chapter 5: Writers and Readers
Part 3: New I/O APIs
Chapter 6: Buffers
Chapter 7: Channels
Chapter 8: Selectors
Chapter 9: Regular Expressions
Chapter 10: Charsets
Chapter 11: Formatter and Scanner
Part 4: More New I/O APIs
Chapter 12: File System APIs
Chapter 13: Asynchronous I/O
Chapter 14: Additional NIO.2 APIs
Appendix A: Answers to Review Exercises

Install java-gnome on Ubuntu 15.10, and first try.

2015-10-29T21:16:00.000-07:00

The java-gnome User Interface Library is a Java bindings for GTK and GNOME. To install it on Ubuntu, enter the command in Terminal:
$ sudo apt-get install libjava-gnome-java

(reference: http://java-gnome.sourceforge.net/get/ubuntu.php)

First try:

Create a my first example ExamplePressMe.java (copt from HERE), under trial directory ~/java-gnome-works.

/*
 * ExamplePressMe.java
 *
 * Copyright (c) 2006-2008 Operational Dynamics Consulting Pty Ltd
 *
 * The code in this file, and the library it is a part of, are made available
 * to you by the authors under the terms of the "GNU General Public Licence,
 * version 2" See the LICENCE file for the terms governing usage and
 * redistribution.
 */
package button;

import org.gnome.gdk.Event;
import org.gnome.gtk.Button;
import org.gnome.gtk.Gtk;
import org.gnome.gtk.Label;
import org.gnome.gtk.VBox;
import org.gnome.gtk.Widget;
import org.gnome.gtk.Window;

/**
 * A simple Window with a Label and a Button in it. Demonstrates the basics of
 * initializing GTK, packing Widgets into Containers, and hooking up signals.
 * 
 * This example has been around, in one form or another, since the very
 * beginnings of java-gnome. If you're just starting out with GTK and GNOME
 * don't worry; we started here too.
 * 
 * @author Andrew Cowie
 * @since 4.0.0
 */
public class ExamplePressMe
{
    public static void main(String[] args) {
        final Window w;
        final VBox x;
        final Label l;
        final Button b;

        /*
         * Initialize GTK. You MUST call this to load the library before
         * trying to use any other elements provided by java-gnome.
         */

        Gtk.init(args);

        /*
         * Create a top level Window. It's the Container around which the
         * window manager draws decorations such as a title bar, minimize and
         * close buttons, resize edges, etc.
         */

        w = new Window();

        /*
         * Since a Window is a Bin, it can only have one child Widget. That's
         * probably not very useful in most cases. To take that one slot and
         * turn it into many, we use a VBox, a Container that will stack its
         * children vertically.
         */

        x = new VBox(false, 3);

        /*
         * Create a Label with some text describing the Button that will
         * follow, then add it to the VBox.
         */

        l = new Label("Go ahead:\nMake my day");
        x.add(l);

        /*
         * Create our Button, with a nice explicit bit of text labelling it
         * and what you're to do.
         */

        b = new Button("Press me!");
        x.add(b);

        /*
         * Now the magic part. Just sitting there, the Button won't do
         * anything. You need to hook up a "signal handler" to deal with the
         * 'clicked' signal. This is how we do it in java-gnome.
         * 
         * Button.Clicked is a Java interface. You create an instance of it to
         * do what you want when the callback happens, and then pass it to the
         * Button's connect() method.
         * 
         * The onClicked() method is what is required by the Button.Clicked
         * interface. Most IDEs will prompt you asking if you want to "Add
         * unimplemented methods?" You bet! And ta-da! You have exactly the
         * signature you need to implement a 'clicked' signal handler.
         * 
         * Since we declared b as final we can use it in the anonymous nested
         * class (yet *another* reason that final is worth using). If the
         * situation were otherwise, then the source parameter can be used to
         * find out what Button was clicked.
         */

        b.connect(new Button.Clicked() {
            public void onClicked(Button source) {
                System.out.println("I was clicked: " + b.getLabel());
            }
        });

        /*
         * Now we pack the VBox into our Window, set the Window's title, and
         * invoke the command to realize everything onto the screen.
         */

        w.add(x);
        w.setTitle("Hello World");
        w.showAll();

        /*
         * We would be be done except for one last detail. Closing a Window
         * does not terminate the application. If that's what you want (and we
         * do indeed want that here) then you need to hook up a handler to do
         * something when the 'delete-event' signal is emitted.
         * 
         * Again, the method here implements the interface.
         */

        w.connect(new Window.DeleteEvent() {
            public boolean onDeleteEvent(Widget source, Event event) {
                Gtk.mainQuit();
                return false;
            }
        });

        /*
         * Now we're ready to run the main loop. The signals we've hooked up
         * handlers for above won't be emitted until the user does something,
         * but no events will be processed until the main loop is running;
         * that's where the signals will come from. This call blocks. You have
         * finished setting things up and now it's up to your signal handlers
         * to carry out the program's logic in response to the user's actions;
         * the essence of event-driven programming.
         */

        Gtk.main();
    }
}

Make a tests directory to hold the output.

Enter the command to compile the java code with java-gnome.
$ javac -classpath /usr/share/java/gtk-4.1.jar -d tests ExamplePressMe.java

Run it:
$ java -classpath /usr/share/java/gtk-4.1.jar:tests button.ExamplePressMe

Where /usr/share/java/gtk-4.1.jar is the installed gtk-4.1.jar.

(reference: http://java-gnome.sourceforge.net/README.html)