Merge branch 'eugenp:master' into master

core-java-modules/core-java-16/README.md

@@ -1,3 +1,4 @@
 ### Relevant articles:
 
 - [Collect a Java Stream to an Immutable Collection](https://www.baeldung.com/java-stream-immutable-collection)
+- [Guide to mapMulti in Stream API](https://www.baeldung.com/java-mapmulti)

core-java-modules/core-java-arrays-operations-advanced/README.md

@@ -10,3 +10,4 @@ This module contains articles about advanced operations on arrays in Java. They
 - [Intersection Between two Integer Arrays](https://www.baeldung.com/java-array-intersection)
 - [Comparing Arrays in Java](https://www.baeldung.com/java-comparing-arrays)
 - [Concatenate Two Arrays in Java](https://www.baeldung.com/java-concatenate-arrays)
+- [Performance of System.arraycopy() vs. Arrays.copyOf()](https://www.baeldung.com/java-system-arraycopy-arrays-copyof-performance)

core-java-modules/core-java-arrays-operations-advanced/pom.xml

@@ -26,10 +26,50 @@
             <version>${assertj-core.version}</version>
             <scope>test</scope>
         </dependency>
+
+        <dependency>
+            <groupId>org.openjdk.jmh</groupId>
+            <artifactId>jmh-core</artifactId>
+            <version>${jmh.version}</version>
+        </dependency>
+
+        <dependency>
+            <groupId>org.openjdk.jmh</groupId>
+            <artifactId>jmh-generator-annprocess</artifactId>
+            <version>${jmh.version}</version>
+        </dependency>
     </dependencies>
 
     <properties>
         <assertj-core.version>3.10.0</assertj-core.version>
+        <jmh.version>1.33</jmh.version>
     </properties>
 
+    <build>
+        <plugins>
+            <plugin>
+                <artifactId>maven-assembly-plugin</artifactId>
+                <configuration>
+                    <descriptorRefs>
+                        <descriptorRef>jar-with-dependencies</descriptorRef>
+                    </descriptorRefs>
+                    <archive>
+                        <manifest>
+                            <mainClass>com.baeldung.copyarraymethodsperformance.BenchmarkRunner</mainClass>
+                        </manifest>
+                    </archive>
+                </configuration>
+                <executions>
+                    <execution>
+                        <id>make-assembly</id>
+                        <phase>package</phase>
+                        <goals>
+                            <goal>single</goal>
+                        </goals>
+                    </execution>
+                </executions>
+            </plugin>
+        </plugins>
+    </build>
+
 </project>

core-java-modules/core-java-arrays-operations-advanced/src/main/java/com/baeldung/copyarraymethodsperformance/BenchmarkRunner.java

@@ -0,0 +1,11 @@
+package com.baeldung.copyarraymethodsperformance;
+
+public class BenchmarkRunner {
+
+    public static void main(String[] args) throws Exception {
+
+        org.openjdk.jmh.Main.main(args);
+
+    }
+
+}

core-java-modules/core-java-arrays-operations-advanced/src/main/java/com/baeldung/copyarraymethodsperformance/ObjectsCopyBenchmark.java

@@ -0,0 +1,42 @@
+package com.baeldung.copyarraymethodsperformance;
+
+import org.openjdk.jmh.annotations.*;
+
+import java.util.Arrays;
+import java.util.Random;
+import java.util.concurrent.TimeUnit;
+
+@BenchmarkMode(Mode.AverageTime)
+@State(Scope.Thread)
+@OutputTimeUnit(TimeUnit.NANOSECONDS)
+@Warmup(iterations = 10)
+@Fork(1)
+@Measurement(iterations = 100)
+public class ObjectsCopyBenchmark {
+
+    @Param({ "10", "1000000" })
+    public int SIZE;
+    Integer[] src;
+
+    @Setup
+    public void setup() {
+        Random r = new Random();
+        src = new Integer[SIZE];
+
+        for (int i = 0; i < SIZE; i++) {
+            src[i] = r.nextInt();
+        }
+    }
+
+    @Benchmark
+    public Integer[] systemArrayCopyBenchmark() {
+        Integer[] target = new Integer[SIZE];
+        System.arraycopy(src, 0, target, 0, SIZE);
+        return target;
+    }
+
+    @Benchmark
+    public Integer[] arraysCopyOfBenchmark() {
+        return Arrays.copyOf(src, SIZE);
+    }
+}

core-java-modules/core-java-arrays-operations-advanced/src/main/java/com/baeldung/copyarraymethodsperformance/PrimitivesCopyBenchmark.java

@@ -0,0 +1,43 @@
+package com.baeldung.copyarraymethodsperformance;
+
+import org.openjdk.jmh.annotations.*;
+
+import java.util.Arrays;
+import java.util.Random;
+import java.util.concurrent.TimeUnit;
+
+@BenchmarkMode(Mode.AverageTime)
+@State(Scope.Thread)
+@OutputTimeUnit(TimeUnit.NANOSECONDS)
+@Warmup(iterations = 10)
+@Fork(1)
+@Measurement(iterations = 100)
+public class PrimitivesCopyBenchmark {
+
+    @Param({ "10", "1000000" })
+    public int SIZE;
+
+    int[] src;
+
+    @Setup
+    public void setup() {
+        Random r = new Random();
+        src = new int[SIZE];
+
+        for (int i = 0; i < SIZE; i++) {
+            src[i] = r.nextInt();
+        }
+    }
+
+    @Benchmark
+    public int[] systemArrayCopyBenchmark() {
+        int[] target = new int[SIZE];
+        System.arraycopy(src, 0, target, 0, SIZE);
+        return target;
+    }
+
+    @Benchmark
+    public int[] arraysCopyOfBenchmark() {
+        return Arrays.copyOf(src, SIZE);
+    }
+}

core-java-modules/core-java-networking-3/README.md

@@ -8,4 +8,5 @@ This module contains articles about networking in Java
 - [Downloading Email Attachments in Java](https://www.baeldung.com/java-download-email-attachments)
 - [Connection Timeout vs. Read Timeout for Java Sockets](https://www.baeldung.com/java-socket-connection-read-timeout)
 - [Find Whether an IP Address Is in the Specified Range or Not in Java](https://www.baeldung.com/java-check-ip-address-range)
+- [Find the IP Address of a Client Connected to a Server](https://www.baeldung.com/java-client-get-ip-address)
 - [[<-- Prev]](/core-java-modules/core-java-networking-2)

core-java-modules/core-java-networking-3/src/main/java/com/baeldung/clientaddress/ApplicationClient.java

@@ -0,0 +1,39 @@
+package com.baeldung.clientaddress;
+
+import java.io.BufferedReader;
+import java.io.IOException;
+import java.io.InputStreamReader;
+import java.io.PrintWriter;
+import java.net.Socket;
+
+public class ApplicationClient {
+
+    private Socket clientSocket;
+    private PrintWriter out;
+    private BufferedReader in;
+
+    public void connect(String ip, int port) throws IOException {
+        clientSocket = new Socket(ip, port);
+        out = new PrintWriter(clientSocket.getOutputStream(), true);
+        in = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));
+    }
+
+    public void sendGreetings(String msg) throws IOException {
+        out.println(msg);
+        String reply = in.readLine();
+        System.out.println("Reply received from the server :: " + reply);
+    }
+
+    public void disconnect() throws IOException {
+        in.close();
+        out.close();
+        clientSocket.close();
+    }
+
+    public static void main(String[] args) throws IOException {
+        ApplicationClient client = new ApplicationClient();
+        client.connect(args[0], Integer.parseInt(args[1])); // IP address and port number of the server
+        client.sendGreetings(args[2]); // greetings message
+        client.disconnect();
+    }
+}

core-java-modules/core-java-networking-3/src/main/java/com/baeldung/clientaddress/ApplicationServer.java

@@ -0,0 +1,51 @@
+package com.baeldung.clientaddress;
+
+import java.io.BufferedReader;
+import java.io.IOException;
+import java.io.InputStreamReader;
+import java.io.PrintWriter;
+import java.net.InetSocketAddress;
+import java.net.ServerSocket;
+import java.net.Socket;
+
+public class ApplicationServer {
+
+    private ServerSocket serverSocket;
+    private Socket connectedSocket;
+    private PrintWriter out;
+    private BufferedReader in;
+
+    public void startServer(int port) throws IOException {
+        serverSocket = new ServerSocket(port);
+        connectedSocket = serverSocket.accept();
+
+        InetSocketAddress socketAddress = (InetSocketAddress) connectedSocket.getRemoteSocketAddress();
+        String clientIpAddress = socketAddress.getAddress()
+            .getHostAddress();
+        System.out.println("IP address of the connected client :: " + clientIpAddress);
+
+        out = new PrintWriter(connectedSocket.getOutputStream(), true);
+        in = new BufferedReader(new InputStreamReader(connectedSocket.getInputStream()));
+        String msg = in.readLine();
+        System.out.println("Message received from the client :: " + msg);
+        out.println("Hello Client !!");
+
+        closeIO();
+        stopServer();
+    }
+
+    private void closeIO() throws IOException {
+        in.close();
+        out.close();
+    }
+
+    private void stopServer() throws IOException {
+        connectedSocket.close();
+        serverSocket.close();
+    }
+
+    public static void main(String[] args) throws IOException {
+        ApplicationServer server = new ApplicationServer();
+        server.startServer(5000);
+    }
+}

core-java-modules/core-java-os/src/main/java/com/baeldung/java9/process/ProcessAPIEnhancements.java

@@ -0,0 +1,101 @@
+package com.baeldung.java9.process;
+
+import java.io.IOException;
+import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.ExecutionException;
+import java.util.stream.Stream;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+public class ProcessAPIEnhancements {
+
+    static Logger log = LoggerFactory.getLogger(ProcessAPIEnhancements.class);
+
+    public static void main(String[] args) throws IOException, InterruptedException, ExecutionException {
+        infoOfCurrentProcess();
+        infoOfLiveProcesses();
+        infoOfSpawnProcess();
+        infoOfExitCallback();
+        infoOfChildProcess();
+    }
+
+    private static void infoOfCurrentProcess() {
+        ProcessHandle processHandle = ProcessHandle.current();
+        ProcessHandle.Info processInfo = processHandle.info();
+
+        log.info("PID: " + processHandle.pid());
+        log.info("Arguments: " + processInfo.arguments());
+        log.info("Command: " + processInfo.command());
+        log.info("Instant: " + processInfo.startInstant());
+        log.info("Total CPU duration: " + processInfo.totalCpuDuration());
+        log.info("User: " + processInfo.user());
+    }
+
+    private static void infoOfSpawnProcess() throws IOException {
+
+        String javaCmd = ProcessUtils.getJavaCmd().getAbsolutePath();
+        ProcessBuilder processBuilder = new ProcessBuilder(javaCmd, "-version");
+        Process process = processBuilder.inheritIO().start();
+        ProcessHandle processHandle = process.toHandle();
+        ProcessHandle.Info processInfo = processHandle.info();
+
+        log.info("PID: " + processHandle.pid());
+        log.info("Arguments: " + processInfo.arguments());
+        log.info("Command: " + processInfo.command());
+        log.info("Instant: " + processInfo.startInstant());
+        log.info("Total CPU duration: " + processInfo.totalCpuDuration());
+        log.info("User: " + processInfo.user());
+    }
+
+    private static void infoOfLiveProcesses() {
+        Stream<ProcessHandle> liveProcesses = ProcessHandle.allProcesses();
+        liveProcesses.filter(ProcessHandle::isAlive)
+            .forEach(ph -> {
+                log.info("PID: " + ph.pid());
+                log.info("Instance: " + ph.info().startInstant());
+                log.info("User: " + ph.info().user());
+            });
+    }
+
+    private static void infoOfChildProcess() throws IOException {
+        int childProcessCount = 5;
+        for (int i = 0; i < childProcessCount; i++) {
+            String javaCmd = ProcessUtils.getJavaCmd()
+              .getAbsolutePath();
+            ProcessBuilder processBuilder
+              = new ProcessBuilder(javaCmd, "-version");
+            processBuilder.inheritIO().start();
+        }
+
+        Stream<ProcessHandle> children = ProcessHandle.current()
+          .children();
+        children.filter(ProcessHandle::isAlive)
+          .forEach(ph -> log.info("PID: {}, Cmd: {}", ph.pid(), ph.info()
+            .command()));
+        Stream<ProcessHandle> descendants = ProcessHandle.current()
+          .descendants();
+        descendants.filter(ProcessHandle::isAlive)
+          .forEach(ph -> log.info("PID: {}, Cmd: {}", ph.pid(), ph.info()
+            .command()));
+    }
+
+    private static void infoOfExitCallback() throws IOException, InterruptedException, ExecutionException {
+        String javaCmd = ProcessUtils.getJavaCmd()
+          .getAbsolutePath();
+        ProcessBuilder processBuilder
+          = new ProcessBuilder(javaCmd, "-version");
+        Process process = processBuilder.inheritIO()
+          .start();
+        ProcessHandle processHandle = process.toHandle();
+
+        log.info("PID: {} has started", processHandle.pid());
+        CompletableFuture<ProcessHandle> onProcessExit = processHandle.onExit();
+        onProcessExit.get();
+        log.info("Alive: " + processHandle.isAlive());
+        onProcessExit.thenAccept(ph -> {
+            log.info("PID: {} has stopped", ph.pid());
+        });
+    }
+
+}

core-java-modules/core-java-os/src/test/java/com/baeldung/java9/process/ProcessAPIEnhancementsUnitTest.java

@@ -1,132 +0,0 @@
-package com.baeldung.java9.process;
-
-import static org.junit.Assert.assertEquals;
-import static org.junit.Assert.assertNotNull;
-import static org.junit.Assert.assertTrue;
-
-import java.io.IOException;
-import java.util.concurrent.CompletableFuture;
-import java.util.stream.Stream;
-
-import org.junit.Test;
-import org.slf4j.Logger;
-import org.slf4j.LoggerFactory;
-
-/**
- * Created by sanaulla on 2/23/2017.
- */
-
-public class ProcessAPIEnhancementsUnitTest {
-
-    Logger log = LoggerFactory.getLogger(ProcessAPIEnhancementsUnitTest.class);
-
-    // @Test
-    // OS / Java version dependent
-    public void givenCurrentProcess_whenInvokeGetInfo_thenSuccess() throws IOException {
-        ProcessHandle processHandle = ProcessHandle.current();
-        ProcessHandle.Info processInfo = processHandle.info();
-        assertNotNull(processHandle.pid());
-        assertEquals(true, processInfo.arguments()
-          .isPresent());
-        assertEquals(true, processInfo.command()
-          .isPresent());
-        assertTrue(processInfo.command()
-          .get()
-          .contains("java"));
-
-        assertEquals(true, processInfo.startInstant()
-          .isPresent());
-        assertEquals(true, processInfo.totalCpuDuration()
-          .isPresent());
-        assertEquals(true, processInfo.user()
-          .isPresent());
-    }
-
-    // @Test
-    // OS / Java version dependent
-    public void givenSpawnProcess_whenInvokeGetInfo_thenSuccess() throws IOException {
-
-        String javaCmd = ProcessUtils.getJavaCmd()
-          .getAbsolutePath();
-        ProcessBuilder processBuilder = new ProcessBuilder(javaCmd, "-version");
-        Process process = processBuilder.inheritIO()
-          .start();
-        ProcessHandle processHandle = process.toHandle();
-        ProcessHandle.Info processInfo = processHandle.info();
-        assertNotNull(processHandle.pid());
-        assertEquals(true, processInfo.arguments()
-          .isPresent());
-        assertEquals(true, processInfo.command()
-          .isPresent());
-        assertTrue(processInfo.command()
-          .get()
-          .contains("java"));
-        assertEquals(true, processInfo.startInstant()
-          .isPresent());
-        assertEquals(false, processInfo.totalCpuDuration()
-          .isPresent());
-        assertEquals(true, processInfo.user()
-          .isPresent());
-    }
-
-    // @Test
-    // OS / Java version dependent
-    public void givenLiveProcesses_whenInvokeGetInfo_thenSuccess() {
-        Stream<ProcessHandle> liveProcesses = ProcessHandle.allProcesses();
-        liveProcesses.filter(ProcessHandle::isAlive)
-            .forEach(ph -> {
-                assertNotNull(ph.pid());
-                assertEquals(true, ph.info()
-                  .startInstant()
-                  .isPresent());
-                assertEquals(true, ph.info()
-                  .user()
-                  .isPresent());
-            });
-    }
-
-    // @Test
-    // OS / Java version dependent
-    public void givenProcess_whenGetChildProcess_thenSuccess() throws IOException {
-        int childProcessCount = 5;
-        for (int i = 0; i < childProcessCount; i++) {
-            String javaCmd = ProcessUtils.getJavaCmd()
-              .getAbsolutePath();
-            ProcessBuilder processBuilder
-              = new ProcessBuilder(javaCmd, "-version");
-            processBuilder.inheritIO().start();
-        }
-
-        Stream<ProcessHandle> children = ProcessHandle.current()
-          .children();
-        children.filter(ProcessHandle::isAlive)
-          .forEach(ph -> log.info("PID: {}, Cmd: {}", ph.pid(), ph.info()
-            .command()));
-        Stream<ProcessHandle> descendants = ProcessHandle.current()
-          .descendants();
-        descendants.filter(ProcessHandle::isAlive)
-          .forEach(ph -> log.info("PID: {}, Cmd: {}", ph.pid(), ph.info()
-            .command()));
-    }
-
-    // @Test
-    // OS / Java version dependent
-    public void givenProcess_whenAddExitCallback_thenSuccess() throws Exception {
-        String javaCmd = ProcessUtils.getJavaCmd()
-          .getAbsolutePath();
-        ProcessBuilder processBuilder
-          = new ProcessBuilder(javaCmd, "-version");
-        Process process = processBuilder.inheritIO()
-          .start();
-        ProcessHandle processHandle = process.toHandle();
-
-        log.info("PID: {} has started", processHandle.pid());
-        CompletableFuture<ProcessHandle> onProcessExit = processHandle.onExit();
-        onProcessExit.get();
-        assertEquals(false, processHandle.isAlive());
-        onProcessExit.thenAccept(ph -> {
-            log.info("PID: {} has stopped", ph.pid());
-        });
-    }
-
-}

core-java-modules/core-java-security-3/README.md

@@ -5,4 +5,5 @@ This module contains articles about core Java Security
 ### Relevant Articles:
 
 - [Secret Key and String Conversion in Java](https://www.baeldung.com/java-secret-key-to-string)
+- [Enabling Unlimited Strength Cryptography in Java](https://www.baeldung.com/jce-enable-unlimited-strength)
 - More articles: [[<-- prev]](/core-java-modules/core-java-security-2)

core-java-modules/core-java-security-3/src/test/java/com/baeldung/cryptography/CryptographyStrengthUnitTest.java

@@ -0,0 +1,17 @@
+package com.baeldung.cryptography;
+
+import org.junit.Test;
+
+import java.security.NoSuchAlgorithmException;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+public class CryptographyStrengthUnitTest {
+    private static final int UNLIMITED_KEY_SIZE = 2147483647;
+
+    @Test
+    public void whenDefaultCheck_thenUnlimitedReturned() throws NoSuchAlgorithmException {
+        int maxKeySize = javax.crypto.Cipher.getMaxAllowedKeyLength("AES");
+        assertThat(maxKeySize).isEqualTo(UNLIMITED_KEY_SIZE);
+    }
+}