[BAEL-10840] - Create a libraries-apache-commons module

2018-12-08 15:29:38 +05:30
parent 5072291b32
commit d737e15c6b
88 changed files with 161 additions and 90 deletions
@@ -0,0 +1,35 @@
+package com.baeldung.commons.beanutils;
+
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+public class Course {
+    private String name;
+    private List<String> codes;
+    private Map<String, Student> enrolledStudent = new HashMap<String, Student>();
+
+    public String getName() {
+        return name;
+    }
+
+    public void setName(String name) {
+        this.name = name;
+    }
+
+    public List<String> getCodes() {
+        return codes;
+    }
+
+    public void setCodes(List<String> codes) {
+        this.codes = codes;
+    }
+
+    public void setEnrolledStudent(String enrolledId, Student student) {
+        enrolledStudent.put(enrolledId, student);
+    }
+
+    public Student getEnrolledStudent(String enrolledId) {
+        return enrolledStudent.get(enrolledId);
+    }
+}
@@ -0,0 +1,35 @@
+package com.baeldung.commons.beanutils;
+
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+public class CourseEntity {
+    private String name;
+    private List<String> codes;
+    private Map<String, Student> students = new HashMap<String, Student>();
+
+    public String getName() {
+        return name;
+    }
+
+    public void setName(String name) {
+        this.name = name;
+    }
+
+    public List<String> getCodes() {
+        return codes;
+    }
+
+    public void setCodes(List<String> codes) {
+        this.codes = codes;
+    }
+
+    public void setStudent(String id, Student student) {
+        students.put(id, student);
+    }
+
+    public Student getStudent(String enrolledId) {
+        return students.get(enrolledId);
+    }
+}
@@ -0,0 +1,34 @@
+package com.baeldung.commons.beanutils;
+
+import java.lang.reflect.InvocationTargetException;
+import java.util.List;
+
+import org.apache.commons.beanutils.BeanUtils;
+import org.apache.commons.beanutils.PropertyUtils;
+
+public class CourseService {
+
+    public static void setValues(Course course, String name, List<String> codes) throws IllegalAccessException, InvocationTargetException, NoSuchMethodException {
+        // Setting the simple properties
+        PropertyUtils.setSimpleProperty(course, "name", name);
+        PropertyUtils.setSimpleProperty(course, "codes", codes);
+    }
+
+    public static void setIndexedValue(Course course, int codeIndex, String code) throws IllegalAccessException, InvocationTargetException, NoSuchMethodException {
+        // Setting the indexed properties
+        PropertyUtils.setIndexedProperty(course, "codes[" + codeIndex + "]", code);
+    }
+
+    public static void setMappedValue(Course course, String enrollId, Student student) throws IllegalAccessException, InvocationTargetException, NoSuchMethodException {
+        // Setting the mapped properties
+        PropertyUtils.setMappedProperty(course, "enrolledStudent(" + enrollId + ")", student);
+    }
+
+    public static String getNestedValue(Course course, String enrollId, String nestedPropertyName) throws IllegalAccessException, InvocationTargetException, NoSuchMethodException {
+        return (String) PropertyUtils.getNestedProperty(course, "enrolledStudent(" + enrollId + ")." + nestedPropertyName);
+    }
+
+    public static void copyProperties(Course course, CourseEntity courseEntity) throws IllegalAccessException, InvocationTargetException {
+        BeanUtils.copyProperties(course, courseEntity);
+    }
+}
@@ -0,0 +1,13 @@
+package com.baeldung.commons.beanutils;
+
+public class Student {
+    private String name;
+
+    public String getName() {
+        return name;
+    }
+
+    public void setName(String name) {
+        this.name = name;
+    }
+}
@@ -0,0 +1,23 @@
+package com.baeldung.commons.chain;
+
+import org.apache.commons.chain.Command;
+import org.apache.commons.chain.Context;
+
+import static com.baeldung.commons.chain.AtmConstants.AMOUNT_LEFT_TO_BE_WITHDRAWN;
+
+public abstract class AbstractDenominationDispenser implements Command {
+
+    @Override
+    public boolean execute(Context context) throws Exception {
+        int amountLeftToBeWithdrawn = (int) context.get(AMOUNT_LEFT_TO_BE_WITHDRAWN);
+        if (amountLeftToBeWithdrawn >= getDenominationValue()) {
+            context.put(getDenominationString(), amountLeftToBeWithdrawn / getDenominationValue());
+            context.put(AMOUNT_LEFT_TO_BE_WITHDRAWN, amountLeftToBeWithdrawn % getDenominationValue());
+        }
+        return false;
+    }
+
+    protected abstract String getDenominationString();
+
+    protected abstract int getDenominationValue();
+}
@@ -0,0 +1,13 @@
+package com.baeldung.commons.chain;
+
+import org.apache.commons.chain.impl.CatalogBase;
+
+import static com.baeldung.commons.chain.AtmConstants.ATM_WITHDRAWAL_CHAIN;
+
+public class AtmCatalog extends CatalogBase {
+
+    public AtmCatalog() {
+        super();
+        addCommand(ATM_WITHDRAWAL_CHAIN, new AtmWithdrawalChain());
+    }
+}
@@ -0,0 +1,10 @@
+package com.baeldung.commons.chain;
+
+public class AtmConstants {
+    public static final String TOTAL_AMOUNT_TO_BE_WITHDRAWN = "totalAmountToBeWithdrawn";
+    public static final String AMOUNT_LEFT_TO_BE_WITHDRAWN = "amountLeftToBeWithdrawn";
+    public static final String NO_OF_HUNDREDS_DISPENSED = "noOfHundredsDispensed";
+    public static final String NO_OF_FIFTIES_DISPENSED = "noOfFiftiesDispensed";
+    public static final String NO_OF_TENS_DISPENSED = "noOfTensDispensed";
+    public static final String ATM_WITHDRAWAL_CHAIN = "atmWithdrawalChain";
+}
@@ -0,0 +1,52 @@
+package com.baeldung.commons.chain;
+
+import org.apache.commons.chain.impl.ContextBase;
+
+public class AtmRequestContext extends ContextBase {
+
+    int totalAmountToBeWithdrawn;
+    int noOfHundredsDispensed;
+    int noOfFiftiesDispensed;
+    int noOfTensDispensed;
+    int amountLeftToBeWithdrawn;
+
+    public int getTotalAmountToBeWithdrawn() {
+        return totalAmountToBeWithdrawn;
+    }
+
+    public void setTotalAmountToBeWithdrawn(int totalAmountToBeWithdrawn) {
+        this.totalAmountToBeWithdrawn = totalAmountToBeWithdrawn;
+    }
+
+    public int getNoOfHundredsDispensed() {
+        return noOfHundredsDispensed;
+    }
+
+    public void setNoOfHundredsDispensed(int noOfHundredsDispensed) {
+        this.noOfHundredsDispensed = noOfHundredsDispensed;
+    }
+
+    public int getNoOfFiftiesDispensed() {
+        return noOfFiftiesDispensed;
+    }
+
+    public void setNoOfFiftiesDispensed(int noOfFiftiesDispensed) {
+        this.noOfFiftiesDispensed = noOfFiftiesDispensed;
+    }
+
+    public int getNoOfTensDispensed() {
+        return noOfTensDispensed;
+    }
+
+    public void setNoOfTensDispensed(int noOfTensDispensed) {
+        this.noOfTensDispensed = noOfTensDispensed;
+    }
+
+    public int getAmountLeftToBeWithdrawn() {
+        return amountLeftToBeWithdrawn;
+    }
+
+    public void setAmountLeftToBeWithdrawn(int amountLeftToBeWithdrawn) {
+        this.amountLeftToBeWithdrawn = amountLeftToBeWithdrawn;
+    }
+}
@@ -0,0 +1,14 @@
+package com.baeldung.commons.chain;
+
+import org.apache.commons.chain.impl.ChainBase;
+
+public class AtmWithdrawalChain extends ChainBase {
+
+    public AtmWithdrawalChain() {
+        super();
+        addCommand(new HundredDenominationDispenser());
+        addCommand(new FiftyDenominationDispenser());
+        addCommand(new TenDenominationDispenser());
+        addCommand(new AuditFilter());
+    }
+}
@@ -0,0 +1,18 @@
+package com.baeldung.commons.chain;
+
+import org.apache.commons.chain.Context;
+import org.apache.commons.chain.Filter;
+
+public class AuditFilter implements Filter {
+
+    @Override
+    public boolean postprocess(Context context, Exception exception) {
+        // Send notification to customer & bank.
+        return false;
+    }
+
+    @Override
+    public boolean execute(Context context) throws Exception {
+        return false;
+    }
+}
@@ -0,0 +1,15 @@
+package com.baeldung.commons.chain;
+
+import static com.baeldung.commons.chain.AtmConstants.NO_OF_FIFTIES_DISPENSED;
+
+public class FiftyDenominationDispenser extends AbstractDenominationDispenser {
+    @Override
+    protected String getDenominationString() {
+        return NO_OF_FIFTIES_DISPENSED;
+    }
+
+    @Override
+    protected int getDenominationValue() {
+        return 50;
+    }
+}
@@ -0,0 +1,15 @@
+package com.baeldung.commons.chain;
+
+import static com.baeldung.commons.chain.AtmConstants.NO_OF_HUNDREDS_DISPENSED;
+
+public class HundredDenominationDispenser extends AbstractDenominationDispenser {
+    @Override
+    protected String getDenominationString() {
+        return NO_OF_HUNDREDS_DISPENSED;
+    }
+
+    @Override
+    protected int getDenominationValue() {
+        return 100;
+    }
+}
@@ -0,0 +1,15 @@
+package com.baeldung.commons.chain;
+
+import static com.baeldung.commons.chain.AtmConstants.NO_OF_TENS_DISPENSED;
+
+public class TenDenominationDispenser extends AbstractDenominationDispenser {
+    @Override
+    protected String getDenominationString() {
+        return NO_OF_TENS_DISPENSED;
+    }
+
+    @Override
+    protected int getDenominationValue() {
+        return 10;
+    }
+}
@@ -0,0 +1,47 @@
+package com.baeldung.commons.collectionutil;
+
+public class Address {
+
+    private String locality;
+    private String city;
+    private String zip;
+
+    public String getLocality() {
+        return locality;
+    }
+
+    public void setLocality(String locality) {
+        this.locality = locality;
+    }
+
+    public String getCity() {
+        return city;
+    }
+
+    public void setCity(String city) {
+        this.city = city;
+    }
+
+    public String getZip() {
+        return zip;
+    }
+
+    public void setZip(String zip) {
+        this.zip = zip;
+    }
+
+    @Override
+    public String toString() {
+        StringBuilder builder = new StringBuilder();
+        builder.append("Address [locality=").append(locality).append(", city=").append(city).append(", zip=").append(zip).append("]");
+        return builder.toString();
+    }
+
+    public Address(String locality, String city, String zip) {
+        super();
+        this.locality = locality;
+        this.city = city;
+        this.zip = zip;
+    }
+
+}
@@ -0,0 +1,118 @@
+package com.baeldung.commons.collectionutil;
+
+public class Customer implements Comparable<Customer> {
+
+    private Integer id;
+    private String name;
+    private Long phone;
+    private String locality;
+    private String city;
+    private String zip;
+
+    public Integer getId() {
+        return id;
+    }
+
+    public void setId(Integer id) {
+        this.id = id;
+    }
+
+    public String getName() {
+        return name;
+    }
+
+    public void setName(String name) {
+        this.name = name;
+    }
+
+    public Long getPhone() {
+        return phone;
+    }
+
+    public void setPhone(Long phone) {
+        this.phone = phone;
+    }
+
+    public String getLocality() {
+        return locality;
+    }
+
+    public void setLocality(String locality) {
+        this.locality = locality;
+    }
+
+    public String getCity() {
+        return city;
+    }
+
+    public void setCity(String city) {
+        this.city = city;
+    }
+
+    public String getZip() {
+        return zip;
+    }
+
+    public void setZip(String zip) {
+        this.zip = zip;
+    }
+
+    public Customer(Integer id, String name, Long phone, String locality, String city, String zip) {
+        super();
+        this.id = id;
+        this.name = name;
+        this.phone = phone;
+        this.locality = locality;
+        this.city = city;
+        this.zip = zip;
+    }
+
+    public Customer(Integer id, String name, Long phone) {
+        super();
+        this.id = id;
+        this.name = name;
+        this.phone = phone;
+    }
+
+    public Customer(String name) {
+        super();
+        this.name = name;
+    }
+
+    @Override
+    public int hashCode() {
+        final int prime = 31;
+        int result = 1;
+        result = prime * result + ((name == null) ? 0 : name.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;
+        Customer other = (Customer) obj;
+        if (name == null) {
+            if (other.name != null)
+                return false;
+        } else if (!name.equals(other.name))
+            return false;
+        return true;
+    }
+
+    public int compareTo(Customer o) {
+        return this.name.compareTo(o.getName());
+    }
+
+    @Override
+    public String toString() {
+        StringBuilder builder = new StringBuilder();
+        builder.append("Customer [id=").append(id).append(", name=").append(name).append(", phone=").append(phone).append("]");
+        return builder.toString();
+    }
+
+}
@@ -0,0 +1,37 @@
+package com.baeldung.commons.dbutils;
+
+public class Email {
+    private Integer id;
+    private Integer employeeId;
+    private String address;
+
+    public Integer getId() {
+        return id;
+    }
+
+    public void setId(Integer id) {
+        this.id = id;
+    }
+
+    public Integer getEmployeeId() {
+        return employeeId;
+    }
+
+    public void setEmployeeId(Integer employeeId) {
+        this.employeeId = employeeId;
+    }
+
+    public String getAddress() {
+        return address;
+    }
+
+    public void setAddress(String address) {
+        this.address = address;
+    }
+
+    @Override
+    public String toString() {
+        return "Email{" + "id=" + id + ", address=" + address + '}';
+    }
+
+}
@@ -0,0 +1,67 @@
+package com.baeldung.commons.dbutils;
+
+import java.util.Date;
+import java.util.List;
+
+public class Employee {
+    private Integer id;
+    private String firstName;
+    private String lastName;
+    private Double salary;
+    private Date hiredDate;
+    private List<Email> emails;
+
+    public Integer getId() {
+        return id;
+    }
+
+    public void setId(Integer id) {
+        this.id = id;
+    }
+
+    public String getFirstName() {
+        return firstName;
+    }
+
+    public void setFirstName(String firstName) {
+        this.firstName = firstName;
+    }
+
+    public String getLastName() {
+        return lastName;
+    }
+
+    public void setLastName(String lastName) {
+        this.lastName = lastName;
+    }
+
+    public Double getSalary() {
+        return salary;
+    }
+
+    public void setSalary(Double salary) {
+        this.salary = salary;
+    }
+
+    public Date getHiredDate() {
+        return hiredDate;
+    }
+
+    public void setHiredDate(Date hiredDate) {
+        this.hiredDate = hiredDate;
+    }
+
+    public List<Email> getEmails() {
+        return emails;
+    }
+
+    public void setEmails(List<Email> emails) {
+        this.emails = emails;
+    }
+
+    @Override
+    public String toString() {
+        return "Employee{" + "id=" + id + ", firstName=" + firstName + ", lastName=" + lastName + ", salary=" + salary + ", hiredDate=" + hiredDate + '}';
+    }
+
+}
@@ -0,0 +1,45 @@
+package com.baeldung.commons.dbutils;
+
+import java.sql.Connection;
+import java.sql.ResultSet;
+import java.sql.SQLException;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import org.apache.commons.dbutils.BasicRowProcessor;
+import org.apache.commons.dbutils.BeanProcessor;
+
+import org.apache.commons.dbutils.QueryRunner;
+import org.apache.commons.dbutils.handlers.BeanListHandler;
+
+public class EmployeeHandler extends BeanListHandler<Employee> {
+
+    private Connection connection;
+
+    public EmployeeHandler(Connection con) {
+        super(Employee.class, new BasicRowProcessor(new BeanProcessor(getColumnsToFieldsMap())));
+        this.connection = con;
+    }
+
+    @Override
+    public List<Employee> handle(ResultSet rs) throws SQLException {
+        List<Employee> employees = super.handle(rs);
+
+        QueryRunner runner = new QueryRunner();
+        BeanListHandler<Email> handler = new BeanListHandler<>(Email.class);
+        String query = "SELECT * FROM email WHERE employeeid = ?";
+        for (Employee employee : employees) {
+            List<Email> emails = runner.query(connection, query, handler, employee.getId());
+            employee.setEmails(emails);
+        }
+        return employees;
+    }
+
+    public static Map<String, String> getColumnsToFieldsMap() {
+        Map<String, String> columnsToFieldsMap = new HashMap<>();
+        columnsToFieldsMap.put("FIRST_NAME", "firstName");
+        columnsToFieldsMap.put("LAST_NAME", "lastName");
+        columnsToFieldsMap.put("HIRED_DATE", "hiredDate");
+        return columnsToFieldsMap;
+    }
+}
@@ -0,0 +1,43 @@
+package com.baeldung.commons.io;
+
+import org.apache.commons.io.FileUtils;
+import org.apache.commons.io.monitor.FileAlterationListener;
+import org.apache.commons.io.monitor.FileAlterationListenerAdaptor;
+import org.apache.commons.io.monitor.FileAlterationMonitor;
+import org.apache.commons.io.monitor.FileAlterationObserver;
+
+import java.io.File;
+
+public class FileMonitor {
+
+    public static void main(String[] args) throws Exception {
+        File folder = FileUtils.getTempDirectory();
+        startFileMonitor(folder);
+    }
+
+    /**
+     * @param folder
+     * @throws Exception
+     */
+    public static void startFileMonitor(File folder) throws Exception {
+        FileAlterationObserver observer = new FileAlterationObserver(folder);
+        FileAlterationMonitor monitor = new FileAlterationMonitor(5000);
+
+        FileAlterationListener fal = new FileAlterationListenerAdaptor() {
+
+            @Override
+            public void onFileCreate(File file) {
+                // on create action
+            }
+
+            @Override
+            public void onFileDelete(File file) {
+                // on delete action
+            }
+        };
+
+        observer.addListener(fal);
+        monitor.addObserver(observer);
+        monitor.start();
+    }
+}
@@ -0,0 +1,87 @@
+package com.baeldung.commons.lang3;
+
+import org.apache.commons.lang3.builder.EqualsBuilder;
+import org.apache.commons.lang3.builder.HashCodeBuilder;
+import org.apache.commons.lang3.builder.ToStringBuilder;
+import org.apache.commons.lang3.concurrent.ConcurrentException;
+import org.apache.commons.lang3.concurrent.BackgroundInitializer;
+
+public class BuilderMethods {
+
+    private final int intValue;
+    private final String strSample;
+
+    public BuilderMethods(final int newId, final String newName) {
+        this.intValue = newId;
+        this.strSample = newName;
+    }
+
+    public int getId() {
+        return this.intValue;
+    }
+
+    public String getName() {
+        return this.strSample;
+    }
+
+    @Override
+    public int hashCode() {
+        return new HashCodeBuilder().append(this.intValue).append(this.strSample).toHashCode();
+    }
+
+    @Override
+    public boolean equals(Object obj) {
+        if (obj instanceof BuilderMethods == false) {
+            return false;
+        }
+        if (this == obj) {
+            return true;
+        }
+        final BuilderMethods otherObject = (BuilderMethods) obj;
+
+        return new EqualsBuilder().append(this.intValue, otherObject.intValue).append(this.strSample, otherObject.strSample).isEquals();
+    }
+
+    @Override
+    public String toString() {
+        return new ToStringBuilder(this).append("INTVALUE", this.intValue).append("STRINGVALUE", this.strSample).toString();
+    }
+
+    public static void main(final String[] arguments) {
+        final BuilderMethods simple1 = new BuilderMethods(1, "The First One");
+        System.out.println(simple1.getName());
+        System.out.println(simple1.hashCode());
+        System.out.println(simple1.toString());
+
+        SampleLazyInitializer sampleLazyInitializer = new SampleLazyInitializer();
+
+        try {
+            sampleLazyInitializer.get();
+        } catch (ConcurrentException e1) {
+            // TODO Auto-generated catch block
+            e1.printStackTrace();
+        }
+
+        SampleBackgroundInitializer sampleBackgroundInitializer = new SampleBackgroundInitializer();
+        sampleBackgroundInitializer.start();
+
+        // Proceed with other tasks instead of waiting for the SampleBackgroundInitializer task to finish.
+
+        try {
+            Object result = sampleBackgroundInitializer.get();
+        } catch (ConcurrentException e) {
+            e.printStackTrace();
+        }
+    }
+}
+
+class SampleBackgroundInitializer extends BackgroundInitializer<String> {
+
+    @Override
+    protected String initialize() throws Exception {
+        return null;
+    }
+
+    // Any complex task that takes some time
+
+}
@@ -0,0 +1,11 @@
+package com.baeldung.commons.lang3;
+
+import org.apache.commons.lang3.concurrent.LazyInitializer;
+
+public class SampleLazyInitializer extends LazyInitializer<SampleObject> {
+
+    @Override
+    protected SampleObject initialize() {
+        return new SampleObject();
+    }
+}
@@ -0,0 +1,7 @@
+package com.baeldung.commons.lang3;
+
+public class SampleObject {
+
+    // Ignored
+
+}
@@ -0,0 +1,8 @@
+package com.baeldung.commons.lang3.application;
+
+public class Application {
+    
+    public static void main(String[] args) {
+        
+    }
+}
@@ -0,0 +1,25 @@
+package com.baeldung.commons.lang3.beans;
+
+public class User {
+
+    private final String name;
+    private final String email;
+
+    public User(String name, String email) {
+        this.name = name;
+        this.email = email;
+    }
+
+    public String getName() {
+        return name;
+    }
+
+    public String getEmail() {
+        return email;
+    }
+
+    @Override
+    public String toString() {
+        return "User{" + "name=" + name + ", email=" + email + '}';
+    }
+}
@@ -0,0 +1,11 @@
+package com.baeldung.commons.lang3.beans;
+
+import org.apache.commons.lang3.concurrent.LazyInitializer;
+
+public class UserInitializer extends LazyInitializer<User> {
+
+    @Override
+    protected User initialize() {
+        return new User("John", "john@domain.com");
+    }
+}
@@ -0,0 +1,97 @@
+package com.baeldung.commons.math3;
+
+import org.apache.commons.math3.stat.Frequency;
+import org.knowm.xchart.CategoryChart;
+import org.knowm.xchart.CategoryChartBuilder;
+import org.knowm.xchart.SwingWrapper;
+import org.knowm.xchart.style.Styler;
+
+import java.util.*;
+
+public class Histogram {
+
+    private Map distributionMap;
+    private int classWidth;
+
+    public Histogram() {
+
+        distributionMap = new TreeMap();
+        classWidth = 10;
+        Map distributionMap = processRawData();
+        List yData = new ArrayList();
+        yData.addAll(distributionMap.values());
+        List xData = Arrays.asList(distributionMap.keySet().toArray());
+
+        CategoryChart chart = buildChart(xData, yData);
+        new SwingWrapper<>(chart).displayChart();
+
+    }
+
+    private CategoryChart buildChart(List xData, List yData) {
+
+        // Create Chart
+        CategoryChart chart = new CategoryChartBuilder().width(800).height(600)
+                .title("Age Distribution")
+                .xAxisTitle("Age Group")
+                .yAxisTitle("Frequency")
+                .build();
+
+        chart.getStyler().setLegendPosition(Styler.LegendPosition.InsideNW);
+        chart.getStyler().setAvailableSpaceFill(0.99);
+        chart.getStyler().setOverlapped(true);
+
+        chart.addSeries("age group", xData, yData);
+
+        return chart;
+    }
+
+    private Map processRawData() {
+
+        List<Integer> datasetList = Arrays.asList(
+          36, 25, 38, 46, 55, 68, 72,
+          55, 36, 38, 67, 45, 22, 48,
+          91, 46, 52, 61, 58, 55);
+        Frequency frequency = new Frequency();
+        datasetList.forEach(d -> frequency.addValue(Double.parseDouble(d.toString())));
+
+        datasetList.stream()
+          .map(d -> Double.parseDouble(d.toString()))
+          .distinct()
+          .forEach(observation -> {
+             long observationFrequency = frequency.getCount(observation);
+             int upperBoundary = (observation > classWidth)
+               ? Math.multiplyExact( (int) Math.ceil(observation / classWidth), classWidth)
+               : classWidth;
+             int lowerBoundary = (upperBoundary > classWidth)
+               ? Math.subtractExact(upperBoundary, classWidth)
+               : 0;
+             String bin = lowerBoundary + "-" + upperBoundary;
+
+             updateDistributionMap(lowerBoundary, bin, observationFrequency);
+
+          });
+
+        return distributionMap;
+    }
+
+    private void updateDistributionMap(int lowerBoundary, String bin, long observationFrequency) {
+
+        int prevLowerBoundary = (lowerBoundary > classWidth) ? lowerBoundary - classWidth : 0;
+        String prevBin = prevLowerBoundary + "-" + lowerBoundary;
+        if(!distributionMap.containsKey(prevBin))
+            distributionMap.put(prevBin, 0);
+
+        if(!distributionMap.containsKey(bin)) {
+            distributionMap.put(bin, observationFrequency);
+        }
+        else {
+            long oldFrequency = Long.parseLong(distributionMap.get(bin).toString());
+            distributionMap.replace(bin, oldFrequency + observationFrequency);
+        }
+    }
+
+    public static void main(String[] args) {
+        new Histogram();
+    }
+
+}
@@ -0,0 +1,63 @@
+package com.baeldung.ftp;
+
+import org.apache.commons.net.PrintCommandListener;
+import org.apache.commons.net.ftp.FTPClient;
+import org.apache.commons.net.ftp.FTPFile;
+import org.apache.commons.net.ftp.FTPReply;
+
+import java.io.*;
+import java.util.Arrays;
+import java.util.Collection;
+import java.util.stream.Collectors;
+
+class FtpClient {
+
+    private final String server;
+    private final int port;
+    private final String user;
+    private final String password;
+    private FTPClient ftp;
+
+    FtpClient(String server, int port, String user, String password) {
+        this.server = server;
+        this.port = port;
+        this.user = user;
+        this.password = password;
+    }
+
+    void open() throws IOException {
+        ftp = new FTPClient();
+
+        ftp.addProtocolCommandListener(new PrintCommandListener(new PrintWriter(System.out)));
+
+        ftp.connect(server, port);
+        int reply = ftp.getReplyCode();
+        if (!FTPReply.isPositiveCompletion(reply)) {
+            ftp.disconnect();
+            throw new IOException("Exception in connecting to FTP Server");
+        }
+
+        ftp.login(user, password);
+    }
+
+    void close() throws IOException {
+        ftp.disconnect();
+    }
+
+    Collection<String> listFiles(String path) throws IOException {
+        FTPFile[] files = ftp.listFiles(path);
+
+        return Arrays.stream(files)
+                .map(FTPFile::getName)
+                .collect(Collectors.toList());
+    }
+
+    void putFileToPath(File file, String path) throws IOException {
+        ftp.storeFile(path, new FileInputStream(file));
+    }
+
+    void downloadFile(String source, String destination) throws IOException {
+        FileOutputStream out = new FileOutputStream(destination);
+        ftp.retrieveFile(source, out);
+    }
+}
@@ -0,0 +1,13 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<configuration>
+    <appender name="STDOUT" class="ch.qos.logback.core.ConsoleAppender">
+        <encoder>
+            <pattern>%d{HH:mm:ss.SSS} [%thread] %-5level %logger{36} - %msg%n
+            </pattern>
+        </encoder>
+    </appender>
+
+    <root level="INFO">
+        <appender-ref ref="STDOUT" />
+    </root>
+</configuration>