Update README.md

core-java-modules/core-java/.gitignore

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+*.class
+
+0.*
+
+#folders#
+/target
+/neoDb*
+/data
+/src/main/webapp/WEB-INF/classes
+*/META-INF/*
+.resourceCache
+
+# Packaged files #
+*.jar
+*.war
+*.ear
+
+# Files generated by integration tests
+backup-pom.xml
+/bin/
+/temp
+
+#IntelliJ specific
+.idea/
+*.iml

core-java-modules/core-java/README.md

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+## Core Java Cookbooks and Examples
+
+### Relevant Articles: 
+- [Java Timer](http://www.baeldung.com/java-timer-and-timertask)
+- [A Guide To Java Regular Expressions API](http://www.baeldung.com/regular-expressions-java)
+- [Getting Started with Java Properties](http://www.baeldung.com/java-properties)
+- [How to Create an Executable JAR with Maven](http://www.baeldung.com/executable-jar-with-maven)
+- [Introduction to Nashorn](http://www.baeldung.com/java-nashorn)
+- [Java Money and the Currency API](http://www.baeldung.com/java-money-and-currency)
+- [JVM Log Forging](http://www.baeldung.com/jvm-log-forging)
+- [How to Find all Getters Returning Null](http://www.baeldung.com/java-getters-returning-null)
+- [How to Get a Name of a Method Being Executed?](http://www.baeldung.com/java-name-of-executing-method)
+- [Introduction to Java Serialization](http://www.baeldung.com/java-serialization)
+- [Guide to UUID in Java](http://www.baeldung.com/java-uuid)
+- [Guide to Escaping Characters in Java RegExps](http://www.baeldung.com/java-regexp-escape-char)
+- [Creating a Java Compiler Plugin](http://www.baeldung.com/java-build-compiler-plugin)
+- [Quick Guide to Java Stack](http://www.baeldung.com/java-stack)
+- [Compiling Java *.class Files with javac](http://www.baeldung.com/javac)
+- [Introduction to Javadoc](http://www.baeldung.com/javadoc)
+- [Guide to the Externalizable Interface in Java](http://www.baeldung.com/java-externalizable)
+- [ASCII Art in Java](http://www.baeldung.com/ascii-art-in-java)
+- [What is the serialVersionUID?](http://www.baeldung.com/java-serial-version-uid)
+- [A Guide to the ResourceBundle](http://www.baeldung.com/java-resourcebundle)
+- [Importance of Main Manifest Attribute in a Self-Executing JAR](http://www.baeldung.com/java-jar-executable-manifest-main-class)
+- [Java Global Exception Handler](http://www.baeldung.com/java-global-exception-handler)
+- [How to Get the Size of an Object in Java](http://www.baeldung.com/java-size-of-object)
+- [Common Java Exceptions](http://www.baeldung.com/java-common-exceptions)
+- [Throw Exception in Optional in Java 8](https://www.baeldung.com/java-optional-throw-exception)
+- [Merging java.util.Properties Objects](https://www.baeldung.com/java-merging-properties)
+- [Java – Try with Resources](https://www.baeldung.com/java-try-with-resources)
+- [Abstract Classes in Java](https://www.baeldung.com/java-abstract-class)
+- [Guide to Character Encoding](https://www.baeldung.com/java-char-encoding)
+- [Graphs in Java](https://www.baeldung.com/java-graphs)
+- [Read and Write User Input in Java](http://www.baeldung.com/java-console-input-output)
+- [Formatting with printf() in Java](https://www.baeldung.com/java-printstream-printf)
+- [Retrieve Fields from a Java Class Using Reflection](https://www.baeldung.com/java-reflection-class-fields)
+- [Introduction to Basic Syntax in Java](https://www.baeldung.com/java-syntax)
+- [Using Curl in Java](https://www.baeldung.com/java-curl)
+- [Finding Leap Years in Java](https://www.baeldung.com/java-leap-year)
+- [Java Bitwise Operators](https://www.baeldung.com/java-bitwise-operators)
+- [Guide to Creating and Running a Jar File in Java](https://www.baeldung.com/java-create-jar)
+- [Making a JSON POST Request With HttpURLConnection](https://www.baeldung.com/httpurlconnection-post)
+- [How to Find an Exception’s Root Cause in Java](https://www.baeldung.com/java-exception-root-cause)
+- [Convert Hex to ASCII in Java](https://www.baeldung.com/java-convert-hex-to-ascii)

core-java-modules/core-java/customers.xml

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+<?xml version="1.0"?>
+<webRowSet xmlns="http://java.sun.com/xml/ns/jdbc" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+xsi:schemaLocation="http://java.sun.com/xml/ns/jdbc http://java.sun.com/xml/ns/jdbc/webrowset.xsd">
+  <properties>
+    <command>SELECT * FROM customers</command>
+    <concurrency>1008</concurrency>
+    <datasource><null/></datasource>
+    <escape-processing>true</escape-processing>
+    <fetch-direction>1000</fetch-direction>
+    <fetch-size>0</fetch-size>
+    <isolation-level>2</isolation-level>
+    <key-columns>
+    </key-columns>
+    <map>
+    </map>
+    <max-field-size>0</max-field-size>
+    <max-rows>0</max-rows>
+    <query-timeout>0</query-timeout>
+    <read-only>true</read-only>
+    <rowset-type>ResultSet.TYPE_SCROLL_INSENSITIVE</rowset-type>
+    <show-deleted>false</show-deleted>
+    <table-name>customers</table-name>
+    <url>jdbc:h2:mem:testdb</url>
+    <sync-provider>
+      <sync-provider-name>com.sun.rowset.providers.RIOptimisticProvider</sync-provider-name>
+      <sync-provider-vendor>Oracle Corporation</sync-provider-vendor>
+      <sync-provider-version>1.0</sync-provider-version>
+      <sync-provider-grade>2</sync-provider-grade>
+      <data-source-lock>1</data-source-lock>
+    </sync-provider>
+  </properties>
+  <metadata>
+    <column-count>2</column-count>
+    <column-definition>
+      <column-index>1</column-index>
+      <auto-increment>false</auto-increment>
+      <case-sensitive>true</case-sensitive>
+      <currency>false</currency>
+      <nullable>0</nullable>
+      <signed>true</signed>
+      <searchable>true</searchable>
+      <column-display-size>11</column-display-size>
+      <column-label>ID</column-label>
+      <column-name>ID</column-name>
+      <schema-name>PUBLIC</schema-name>
+      <column-precision>10</column-precision>
+      <column-scale>0</column-scale>
+      <table-name>CUSTOMERS</table-name>
+      <catalog-name>TESTDB</catalog-name>
+      <column-type>4</column-type>
+      <column-type-name>INTEGER</column-type-name>
+    </column-definition>
+    <column-definition>
+      <column-index>2</column-index>
+      <auto-increment>false</auto-increment>
+      <case-sensitive>true</case-sensitive>
+      <currency>false</currency>
+      <nullable>0</nullable>
+      <signed>true</signed>
+      <searchable>true</searchable>
+      <column-display-size>50</column-display-size>
+      <column-label>NAME</column-label>
+      <column-name>NAME</column-name>
+      <schema-name>PUBLIC</schema-name>
+      <column-precision>50</column-precision>
+      <column-scale>0</column-scale>
+      <table-name>CUSTOMERS</table-name>
+      <catalog-name>TESTDB</catalog-name>
+      <column-type>12</column-type>
+      <column-type-name>VARCHAR</column-type-name>
+    </column-definition>
+  </metadata>
+  <data>
+    <currentRow>
+      <columnValue>1</columnValue>
+      <columnValue>Customer1</columnValue>
+    </currentRow>
+    <currentRow>
+      <columnValue>2</columnValue>
+      <columnValue>Customer2</columnValue>
+    </currentRow>
+    <currentRow>
+      <columnValue>3</columnValue>
+      <columnValue>Customer3</columnValue>
+    </currentRow>
+    <currentRow>
+      <columnValue>4</columnValue>
+      <columnValue>Customer4</columnValue>
+    </currentRow>
+    <currentRow>
+      <columnValue>5</columnValue>
+      <columnValue>Customer5</columnValue>
+    </currentRow>
+  </data>
+</webRowSet>

core-java-modules/core-java/src/main/java/com/baeldung/.gitignore

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+*.class
+
+#folders#
+/target
+/neoDb*
+/data
+/src/main/webapp/WEB-INF/classes
+*/META-INF/*
+
+# Packaged files #
+*.jar
+*.war
+*.ear

core-java-modules/core-java/src/main/java/com/baeldung/abstractclasses/application/Application.java

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+package com.baeldung.abstractclasses.application;
+
+import com.baeldung.abstractclasses.filereaders.BaseFileReader;
+import com.baeldung.abstractclasses.filereaders.LowercaseFileReader;
+import com.baeldung.abstractclasses.filereaders.UppercaseFileReader;
+import java.io.IOException;
+import java.net.URISyntaxException;
+import java.nio.file.Path;
+import java.nio.file.Paths;
+
+public class Application {
+
+    public static void main(String[] args) throws IOException, URISyntaxException {
+
+        Application application = new Application();
+        Path path = application.getPathFromResourcesFile("files/test.txt");
+        BaseFileReader lowercaseFileReader = new LowercaseFileReader(path);
+        lowercaseFileReader.readFile().forEach(line -> System.out.println(line));
+        
+        BaseFileReader uppercaseFileReader = new UppercaseFileReader(path);
+        uppercaseFileReader.readFile().forEach(line -> System.out.println(line));
+
+    }
+    
+    private Path getPathFromResourcesFile(String filePath) throws URISyntaxException {
+        return Paths.get(getClass().getClassLoader().getResource(filePath).toURI());
+         
+    }
+}

core-java-modules/core-java/src/main/java/com/baeldung/abstractclasses/filereaders/BaseFileReader.java

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+package com.baeldung.abstractclasses.filereaders;
+
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.List;
+import java.util.stream.Collectors;
+
+public abstract class BaseFileReader {
+    
+    protected Path filePath;
+    
+    protected BaseFileReader(Path filePath) {
+        this.filePath = filePath;
+    }
+    
+    public Path getFilePath() {
+        return filePath;
+    }
+    
+    public List<String> readFile() throws IOException {
+        return Files.lines(filePath)
+            .map(this::mapFileLine).collect(Collectors.toList());
+    }
+    
+    protected abstract String mapFileLine(String line);
+}

core-java-modules/core-java/src/main/java/com/baeldung/abstractclasses/filereaders/LowercaseFileReader.java

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+package com.baeldung.abstractclasses.filereaders;
+
+import java.nio.file.Path;
+
+public class LowercaseFileReader extends BaseFileReader {
+
+    public LowercaseFileReader(Path filePath) {
+        super(filePath);
+    }
+
+    @Override
+    public String mapFileLine(String line) {
+        return line.toLowerCase();
+    }   
+}

core-java-modules/core-java/src/main/java/com/baeldung/abstractclasses/filereaders/UppercaseFileReader.java

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+package com.baeldung.abstractclasses.filereaders;
+
+import java.nio.file.Path;
+
+public class UppercaseFileReader extends BaseFileReader {
+
+    public UppercaseFileReader(Path filePath) {
+        super(filePath);
+    }
+
+    @Override
+    public String mapFileLine(String line) {
+        return line.toUpperCase();
+    }
+}

core-java-modules/core-java/src/main/java/com/baeldung/asciiart/AsciiArt.java

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+package com.baeldung.asciiart;
+
+import java.awt.Font;
+import java.awt.Graphics;
+import java.awt.Graphics2D;
+import java.awt.RenderingHints;
+import java.awt.image.BufferedImage;
+
+public class AsciiArt {
+
+    public AsciiArt() {
+    }
+
+    public void drawString(String text, String artChar, Settings settings) {
+        BufferedImage image = getImageIntegerMode(settings.width, settings.height);
+
+        Graphics2D graphics2D = getGraphics2D(image.getGraphics(), settings);
+        graphics2D.drawString(text, 6, ((int) (settings.height * 0.67)));
+
+        for (int y = 0; y < settings.height; y++) {
+            StringBuilder stringBuilder = new StringBuilder();
+
+            for (int x = 0; x < settings.width; x++) {
+                stringBuilder.append(image.getRGB(x, y) == -16777216 ? " " : artChar);
+            }
+
+            if (stringBuilder.toString()
+                .trim()
+                .isEmpty()) {
+                continue;
+            }
+
+            System.out.println(stringBuilder);
+        }
+
+    }
+
+    private BufferedImage getImageIntegerMode(int width, int height) {
+        return new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
+    }
+
+    private Graphics2D getGraphics2D(Graphics graphics, Settings settings) {
+        graphics.setFont(settings.font);
+
+        Graphics2D graphics2D = (Graphics2D) graphics;
+        graphics2D.setRenderingHint(RenderingHints.KEY_TEXT_ANTIALIASING, RenderingHints.VALUE_TEXT_ANTIALIAS_ON);
+
+        return graphics2D;
+    }
+
+    public class Settings {
+        public Font font;
+        public int width;
+        public int height;
+
+        public Settings(Font font, int width, int height) {
+            this.font = font;
+            this.width = width;
+            this.height = height;
+        }
+    }
+}

core-java-modules/core-java/src/main/java/com/baeldung/basicsyntax/SimpleAddition.java

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+package com.baeldung.basicsyntax;
+
+public class SimpleAddition {
+
+    public static void main(String[] args) {
+        int a = 10;
+        int b = 5;
+        double c = a + b;
+        System.out.println( a + " + " + b + " = " + c);
+    }
+}

core-java-modules/core-java/src/main/java/com/baeldung/console/ConsoleConsoleClass.java

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+package com.baeldung.console;
+
+import java.io.Console;
+
+public class ConsoleConsoleClass {
+
+    public static void main(String[] args) {
+        Console console = System.console();
+
+        if (console == null) {
+            System.out.print("No console available");
+            return;
+        }
+
+        String progLanguauge = console.readLine("Enter your favourite programming language: ");
+        console.printf(progLanguauge + " is very interesting!");
+
+        char[] pass = console.readPassword("To finish, enter password: ");
+        
+        if ("BAELDUNG".equals(pass.toString().toUpperCase()))
+            console.printf("Good! Regards!");
+        else 
+            console.printf("Nice try. Regards.");
+
+    }
+}

core-java-modules/core-java/src/main/java/com/baeldung/console/ConsoleScannerClass.java

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+package com.baeldung.console;
+
+import java.io.BufferedReader;
+import java.io.IOException;
+import java.io.InputStreamReader;
+import java.util.Scanner;
+import java.util.regex.Pattern;
+
+public class ConsoleScannerClass {
+
+    public static void main(String[] args) {
+        System.out.println("Please enter your name and surname: ");
+
+        Scanner scanner = new Scanner(System.in);
+
+        String nameSurname = scanner.nextLine();
+
+        System.out.println("Please enter your gender: ");
+
+        char gender = scanner.next().charAt(0);
+
+        System.out.println("Please enter your age: ");
+
+        int age = scanner.nextInt();
+
+        System.out.println("Please enter your height in meters: ");
+
+        double height = scanner.nextDouble();
+
+        System.out.println(nameSurname + ", " + age + ", is a great " + (gender == 'm' ? "guy" : "girl") + " with " + height + " meters height" + " and " + (gender == 'm' ? "he" : "she") + " reads Baeldung.");
+
+        System.out.print("Have a good");
+        System.out.print(" one!");
+
+        System.out.println("\nPlease enter number of years of experience as a developer: ");
+
+        BufferedReader buffReader = new BufferedReader(new InputStreamReader(System.in));
+
+        int i = 0;
+
+        try {
+            i = Integer.parseInt(buffReader.readLine());
+        } catch (NumberFormatException e) {
+            // TODO Auto-generated catch block
+            e.printStackTrace();
+        } catch (IOException e) {
+            // TODO Auto-generated catch block
+            e.printStackTrace();
+        }
+
+        System.out.println("You are a " + (i > 5 ? "great" : "good") + " developer!");
+
+        int sum = 0, count = 0;
+
+        System.out.println("Please enter your college degrees. To finish, enter baeldung website url");
+
+        while (scanner.hasNextInt()) {
+            int nmbr = scanner.nextInt();
+            sum += nmbr;
+            count++;
+        }
+        int mean = sum / count;
+
+        System.out.println("Your average degree is " + mean);
+
+        if (scanner.hasNext(Pattern.compile("www.baeldung.com")))
+            System.out.println("Correct!");
+        else
+            System.out.println("Baeldung website url is www.baeldung.com");
+
+        if (scanner != null)
+            scanner.close();
+
+    }
+
+}

core-java-modules/core-java/src/main/java/com/baeldung/deserialization/AppleProduct.java

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+package com.baeldung.deserialization;
+
+import java.io.Serializable;
+
+public class AppleProduct implements Serializable {
+
+    private static final long serialVersionUID = 1234567L; // user-defined (i.e. not default or generated)
+    // private static final long serialVersionUID = 7654321L; // user-defined (i.e. not default or generated)
+
+    public String headphonePort;
+    public String thunderboltPort;
+    public String lightningPort;
+
+    public String getHeadphonePort() {
+        return headphonePort;
+    }
+
+    public String getThunderboltPort() {
+        return thunderboltPort;
+    }
+
+    public static long getSerialVersionUID() {
+        return serialVersionUID;
+    }
+
+    public String getLightningPort() {
+        return lightningPort;
+    }
+
+}

core-java-modules/core-java/src/main/java/com/baeldung/deserialization/DeserializationUtility.java

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+package com.baeldung.deserialization;
+
+import java.io.ByteArrayInputStream;
+import java.io.IOException;
+import java.io.ObjectInputStream;
+import java.util.Base64;
+
+public class DeserializationUtility {
+
+    public static void main(String[] args) throws ClassNotFoundException, IOException {
+
+        String serializedObj = "rO0ABXNyACljb20uYmFlbGR1bmcuZGVzZXJpYWxpemF0aW9uLkFwcGxlUHJvZHVjdAAAAAAAEtaHAgADTAANaGVhZHBob25lUG9ydHQAEkxqYXZhL2xhbmcvU3RyaW5nO0wADWxpZ2h0bmluZ1BvcnRxAH4AAUwAD3RodW5kZXJib2x0UG9ydHEAfgABeHB0ABFoZWFkcGhvbmVQb3J0MjAyMHQAEWxpZ2h0bmluZ1BvcnQyMDIwdAATdGh1bmRlcmJvbHRQb3J0MjAyMA==";
+        System.out.println("Deserializing AppleProduct...");
+        AppleProduct deserializedObj = (AppleProduct) deSerializeObjectFromString(serializedObj);
+        System.out.println("Headphone port of AppleProduct:" + deserializedObj.getHeadphonePort());
+        System.out.println("Thunderbolt port of AppleProduct:" + deserializedObj.getThunderboltPort());
+        System.out.println("LightningPort port of AppleProduct:" + deserializedObj.getLightningPort());
+    }
+
+    public static Object deSerializeObjectFromString(String s) throws IOException, ClassNotFoundException {
+        byte[] data = Base64.getDecoder().decode(s);
+        ObjectInputStream ois = new ObjectInputStream(new ByteArrayInputStream(data));
+        Object o = ois.readObject();
+        ois.close();
+        return o;
+    }
+
+}

core-java-modules/core-java/src/main/java/com/baeldung/deserialization/SerializationUtility.java

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+package com.baeldung.deserialization;
+
+import java.io.ByteArrayOutputStream;
+import java.io.IOException;
+import java.io.ObjectOutputStream;
+import java.io.Serializable;
+import java.util.Base64;
+
+public class SerializationUtility {
+
+    public static void main(String[] args) throws ClassNotFoundException, IOException {
+
+        AppleProduct macBook = new AppleProduct();
+        macBook.headphonePort = "headphonePort2020";
+        macBook.thunderboltPort = "thunderboltPort2020";
+        macBook.lightningPort = "lightningPort2020";
+
+        String serializedObj = serializeObjectToString(macBook);
+        System.out.println("Serialized AppleProduct object to string:");
+        System.out.println(serializedObj);
+    }
+
+    public static String serializeObjectToString(Serializable o) throws IOException {
+        ByteArrayOutputStream baos = new ByteArrayOutputStream();
+        ObjectOutputStream oos = new ObjectOutputStream(baos);
+        oos.writeObject(o);
+        oos.close();
+        return Base64.getEncoder().encodeToString(baos.toByteArray());
+    }
+
+}

core-java-modules/core-java/src/main/java/com/baeldung/encoding/CharacterEncodingExamples.java

@@ -0,0 +1,45 @@
+package com.baeldung.encoding;
+
+import java.io.BufferedReader;
+import java.io.ByteArrayInputStream;
+import java.io.File;
+import java.io.FileInputStream;
+import java.io.IOException;
+import java.io.InputStreamReader;
+import java.io.UnsupportedEncodingException;
+import java.nio.charset.Charset;
+import java.nio.charset.CharsetDecoder;
+import java.nio.charset.CodingErrorAction;
+
+public class CharacterEncodingExamples {
+
+    static String readFile(String filePath, String encoding) throws IOException {
+        File file = new File(filePath);
+        StringBuffer buffer = new StringBuffer();
+        try (InputStreamReader isr = new InputStreamReader(new FileInputStream(file), encoding)) {
+            int data;
+            while ((data = isr.read()) != -1) {
+                buffer.append((char) data);
+            }
+        }
+        return buffer.toString();
+    }
+
+    static String convertToBinary(String input, String encoding) throws UnsupportedEncodingException {
+        byte[] bytes = input.getBytes(encoding);
+        StringBuffer buffer = new StringBuffer();
+        for (int b : bytes) {
+            buffer.append(Integer.toBinaryString((b + 256) % 256));
+            buffer.append(" ");
+        }
+        return buffer.toString();
+    }
+
+    static String decodeText(String input, Charset charset, CodingErrorAction codingErrorAction) throws IOException {
+        CharsetDecoder charsetDecoder = charset.newDecoder();
+        charsetDecoder.onMalformedInput(codingErrorAction);
+        return new BufferedReader(
+          new InputStreamReader(
+            new ByteArrayInputStream(input.getBytes()), charsetDecoder)).readLine();
+    }
+}

core-java-modules/core-java/src/main/java/com/baeldung/executable/ExecutableMavenJar.java

@@ -0,0 +1,11 @@
+package com.baeldung.executable;
+
+import javax.swing.JOptionPane;
+
+public class ExecutableMavenJar {
+
+    public static void main(String[] args) {
+        JOptionPane.showMessageDialog(null, "It worked!", "Executable Jar with Maven", 1);
+    }
+
+}

core-java-modules/core-java/src/main/java/com/baeldung/externalizable/Community.java

@@ -0,0 +1,23 @@
+package com.baeldung.externalizable;
+
+import java.io.*;
+
+public class Community implements Serializable {
+
+    private int id;
+
+    public int getId() {
+        return id;
+    }
+
+    public void setId(int id) {
+        this.id = id;
+    }
+
+    @Override
+    public String toString() {
+        return "Community{" +
+                "id=" + id +
+                '}';
+    }
+}

core-java-modules/core-java/src/main/java/com/baeldung/externalizable/Country.java

@@ -0,0 +1,62 @@
+package com.baeldung.externalizable;
+
+import java.io.Externalizable;
+import java.io.IOException;
+import java.io.ObjectInput;
+import java.io.ObjectOutput;
+
+public class Country implements Externalizable {
+
+    private static final long serialVersionUID = 1L;
+
+    private String name;
+    private String capital;
+    private int code;
+
+    public String getName() {
+        return name;
+    }
+
+    public void setName(String name) {
+        this.name = name;
+    }
+
+    public String getCapital() {
+        return capital;
+    }
+
+    public void setCapital(String capital) {
+        this.capital = capital;
+    }
+
+    public int getCode() {
+        return code;
+    }
+
+    public void setCode(int code) {
+        this.code = code;
+    }
+
+    @Override
+    public void writeExternal(ObjectOutput out) throws IOException {
+        out.writeUTF(name);
+        out.writeUTF(capital);
+        out.writeInt(code);
+    }
+
+    @Override
+    public void readExternal(ObjectInput in) throws IOException, ClassNotFoundException {
+        this.name = in.readUTF();
+        this.capital = in.readUTF();
+        this.code = in.readInt();
+    }
+
+    @Override
+    public String toString() {
+        return "Country{" +
+                "name='" + name + '\'' +
+                ", capital='" + capital + '\'' +
+                ", code=" + code +
+                '}';
+    }
+}

core-java-modules/core-java/src/main/java/com/baeldung/externalizable/Region.java

@@ -0,0 +1,57 @@
+package com.baeldung.externalizable;
+
+import java.io.Externalizable;
+import java.io.IOException;
+import java.io.ObjectInput;
+import java.io.ObjectOutput;
+
+public class Region extends Country implements Externalizable {
+
+    private static final long serialVersionUID = 1L;
+
+    private String climate;
+    private Double population;
+    private Community community;
+
+    public String getClimate() {
+        return climate;
+    }
+
+    public void setClimate(String climate) {
+        this.climate = climate;
+    }
+
+    public Double getPopulation() {
+        return population;
+    }
+
+    public void setPopulation(Double population) {
+        this.population = population;
+    }
+
+    @Override
+    public void writeExternal(ObjectOutput out) throws IOException {
+        super.writeExternal(out);
+        out.writeUTF(climate);
+        community = new Community();
+        community.setId(5);
+        out.writeObject(community);
+    }
+
+    @Override
+    public void readExternal(ObjectInput in) throws IOException, ClassNotFoundException {
+        super.readExternal(in);
+        this.climate = in.readUTF();
+        community = (Community) in.readObject();
+    }
+
+    @Override
+    public String toString() {
+        return "Region = {" +
+                "country='" + super.toString() + '\'' +
+                "community='" + community.toString() + '\'' +
+                "climate='" + climate + '\'' +
+                ", population=" + population +
+                '}';
+    }
+}

core-java-modules/core-java/src/main/java/com/baeldung/fileparser/BufferedReaderExample.java

@@ -0,0 +1,24 @@
+package com.baeldung.fileparser;
+
+import java.io.BufferedReader;
+import java.io.FileReader;
+import java.io.IOException;
+import java.util.ArrayList;
+
+public class BufferedReaderExample {
+
+    protected static ArrayList<String> generateArrayListFromFile(String filename) throws IOException {
+
+        ArrayList<String> result = new ArrayList<>();
+
+        try (BufferedReader br = new BufferedReader(new FileReader(filename))) {
+
+            while (br.ready()) {
+                result.add(br.readLine());
+            }
+            return result;
+        }
+
+    }
+
+}

core-java-modules/core-java/src/main/java/com/baeldung/fileparser/FileReaderExample.java

@@ -0,0 +1,31 @@
+package com.baeldung.fileparser;
+
+import java.io.FileReader;
+import java.io.IOException;
+import java.util.ArrayList;
+
+public class FileReaderExample {
+
+    protected static ArrayList<String> generateArrayListFromFile(String filename) throws IOException {
+
+        ArrayList<String> result = new ArrayList<>();
+
+        try (FileReader f = new FileReader(filename)) {
+            StringBuffer sb = new StringBuffer();
+            while (f.ready()) {
+                char c = (char) f.read();
+                if (c == '\n') {
+                    result.add(sb.toString());
+                    sb = new StringBuffer();
+                } else {
+                    sb.append(c);
+                }
+            }
+            if (sb.length() > 0) {
+                result.add(sb.toString());
+            }
+        }
+        
+        return result;
+    }
+}

core-java-modules/core-java/src/main/java/com/baeldung/fileparser/FilesReadLinesExample.java

@@ -0,0 +1,18 @@
+package com.baeldung.fileparser;
+
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Paths;
+import java.util.ArrayList;
+import java.util.List;
+
+public class FilesReadLinesExample {
+
+    protected static ArrayList<String> generateArrayListFromFile(String filename) throws IOException {
+        
+        List<String> result = Files.readAllLines(Paths.get(filename));
+        
+        return (ArrayList<String>) result;
+    }
+
+}

core-java-modules/core-java/src/main/java/com/baeldung/fileparser/ScannerIntExample.java

@@ -0,0 +1,24 @@
+package com.baeldung.fileparser;
+
+import java.io.FileReader;
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.Scanner;
+
+public class ScannerIntExample {
+
+    protected static ArrayList<Integer> generateArrayListFromFile(String filename) throws IOException {
+        
+        ArrayList<Integer> result = new ArrayList<>();
+
+        try (Scanner s = new Scanner(new FileReader(filename))) {
+
+            while (s.hasNext()) {
+                result.add(s.nextInt());
+            }
+            return result;
+        }
+
+    }
+
+}

core-java-modules/core-java/src/main/java/com/baeldung/fileparser/ScannerStringExample.java

@@ -0,0 +1,24 @@
+package com.baeldung.fileparser;
+
+import java.io.FileReader;
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.Scanner;
+
+public class ScannerStringExample {
+
+    protected static ArrayList<String> generateArrayListFromFile(String filename) throws IOException {
+        
+        ArrayList<String> result = new ArrayList<>();
+
+        try (Scanner s = new Scanner(new FileReader(filename))) {
+
+            while (s.hasNext()) {
+                result.add(s.nextLine());
+            }
+            return result;
+        }
+
+    }
+
+}

core-java-modules/core-java/src/main/java/com/baeldung/filesystem/jndi/LookupFSJNDI.java

@@ -0,0 +1,42 @@
+package com.baeldung.filesystem.jndi;
+
+import java.io.File;
+import java.util.Hashtable;
+
+import javax.naming.Context;
+import javax.naming.InitialContext;
+import javax.naming.NamingException;
+
+public class LookupFSJNDI {
+    private InitialContext ctx = null;
+
+    public LookupFSJNDI() throws NamingException {
+        super();
+        init();
+    }
+
+    private void init() throws NamingException {
+        Hashtable<String, String> env = new Hashtable<String, String>();
+
+        env.put(Context.INITIAL_CONTEXT_FACTORY, "com.sun.jndi.fscontext.RefFSContextFactory");
+        // URI to namespace (actual directory)
+        env.put(Context.PROVIDER_URL, "file:./src/test/resources");
+
+        ctx = new InitialContext(env);
+    }
+
+    public InitialContext getCtx() {
+        return ctx;
+    }
+
+    public File getFile(String fileName) {
+        File file;
+        try {
+            file = (File) getCtx().lookup(fileName);
+        } catch (NamingException e) {
+            file = null;
+        }
+        return file;
+    }
+
+}

core-java-modules/core-java/src/main/java/com/baeldung/graph/Graph.java

@@ -0,0 +1,101 @@
+package com.baeldung.graph;
+
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.stream.Collectors;
+
+public class Graph {
+    private Map<Vertex, List<Vertex>> adjVertices;
+
+    Graph() {
+        this.adjVertices = new HashMap<Vertex, List<Vertex>>();
+    }
+
+    void addVertex(String label) {
+        adjVertices.putIfAbsent(new Vertex(label), new ArrayList<>());
+    }
+
+    void removeVertex(String label) {
+        Vertex v = new Vertex(label);
+        adjVertices.values().stream().forEach(e -> e.remove(v));
+        adjVertices.remove(new Vertex(label));
+    }
+
+    void addEdge(String label1, String label2) {
+        Vertex v1 = new Vertex(label1);
+        Vertex v2 = new Vertex(label2);
+        adjVertices.get(v1).add(v2);
+        adjVertices.get(v2).add(v1);
+    }
+
+    void removeEdge(String label1, String label2) {
+        Vertex v1 = new Vertex(label1);
+        Vertex v2 = new Vertex(label2);
+        List<Vertex> eV1 = adjVertices.get(v1);
+        List<Vertex> eV2 = adjVertices.get(v2);
+        if (eV1 != null)
+            eV1.remove(v2);
+        if (eV2 != null)
+            eV2.remove(v1);
+    }
+
+    List<Vertex> getAdjVertices(String label) {
+        return adjVertices.get(new Vertex(label));
+    }
+    
+    String printGraph() {
+        StringBuffer sb = new StringBuffer();
+        for(Vertex v : adjVertices.keySet()) {
+            sb.append(v);
+            sb.append(adjVertices.get(v));
+        }
+        return sb.toString();
+    }
+
+    class Vertex {
+        String label;
+        Vertex(String label) {
+            this.label = label;
+        }
+        
+        @Override
+        public int hashCode() {
+            final int prime = 31;
+            int result = 1;
+            result = prime * result + getOuterType().hashCode();
+            result = prime * result + ((label == null) ? 0 : label.hashCode());
+            return result;
+        }
+        
+        @Override
+        public boolean equals(Object obj) {
+            if (this == obj)
+                return true;
+            if (obj == null)
+                return false;
+            if (getClass() != obj.getClass())
+                return false;
+            Vertex other = (Vertex) obj;
+            if (!getOuterType().equals(other.getOuterType()))
+                return false;
+            if (label == null) {
+                if (other.label != null)
+                    return false;
+            } else if (!label.equals(other.label))
+                return false;
+            return true;
+        }
+
+        @Override
+        public String toString() {
+            return label;
+        }
+
+
+        private Graph getOuterType() {
+            return Graph.this;
+        }
+    }
+}

core-java-modules/core-java/src/main/java/com/baeldung/graph/GraphTraversal.java

@@ -0,0 +1,44 @@
+package com.baeldung.graph;
+
+import java.util.LinkedHashSet;
+import java.util.LinkedList;
+import java.util.Queue;
+import java.util.Set;
+import java.util.Stack;
+
+import com.baeldung.graph.Graph.Vertex;
+
+public class GraphTraversal {
+    static Set<String> depthFirstTraversal(Graph graph, String root) {
+        Set<String> visited = new LinkedHashSet<String>();
+        Stack<String> stack = new Stack<String>();
+        stack.push(root);
+        while (!stack.isEmpty()) {
+            String vertex = stack.pop();
+            if (!visited.contains(vertex)) {
+                visited.add(vertex);
+                for (Vertex v : graph.getAdjVertices(vertex)) {              
+                    stack.push(v.label);
+                }
+            }
+        }
+        return visited;
+    }
+
+    static Set<String> breadthFirstTraversal(Graph graph, String root) {
+        Set<String> visited = new LinkedHashSet<String>();
+        Queue<String> queue = new LinkedList<String>();
+        queue.add(root);
+        visited.add(root);
+        while (!queue.isEmpty()) {
+            String vertex = queue.poll();
+            for (Vertex v : graph.getAdjVertices(vertex)) {
+                if (!visited.contains(v.label)) {
+                    visited.add(v.label);
+                    queue.add(v.label);
+                }
+            }
+        }
+        return visited;
+    }
+}