Kiview ftpclient (#4456)

* Add example for FTP client

Using Apache Commons Net

* Add missing resource

* Fix wrong file download in integration test

* Add example for using FTP support in JDK

* Close input stream after copy

* Fix test name

libraries/src/main/java/com/baeldung/ftp/FtpClient.java

@@ -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);
+    }
+}