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bhaskar16bhaskar16
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[BAEL-7817] Java 22 intro (#16454)
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+341
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lines changed

‎core-java-modules/core-java-22/pom.xml

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<?xml version="1.0" encoding="UTF-8"?>
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<project xmlns="http://maven.apache.org/POM/4.0.0"
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xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
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xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
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<modelVersion>4.0.0</modelVersion>
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<parent>
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<groupId>com.baeldung.core-java-modules</groupId>
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<artifactId>core-java-modules</artifactId>
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<version>0.0.1-SNAPSHOT</version>
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</parent>
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<artifactId>core-java-22</artifactId>
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<properties>
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<maven.compiler.source>22</maven.compiler.source>
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<maven.compiler.target>22</maven.compiler.target>
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<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
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<java.version>22</java.version>
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</properties>
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<build>
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<plugins>
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<plugin>
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<groupId>org.apache.maven.plugins</groupId>
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<artifactId>maven-compiler-plugin</artifactId>
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<configuration>
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<source>22</source>
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<target>22</target>
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<compilerArgs>--enable-preview</compilerArgs>
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</configuration>
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</plugin>
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</plugins>
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</build>
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</project>

‎core-java-modules/core-java-22/src/main/java/com/baeldung/javafeatures/ImplicitClassDeclaration.java

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void main() {
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System.out.println("This is an implicitly declared class without any constructs");
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int x = 165;
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int y = 100;
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System.out.println(y + x);
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}

‎core-java-modules/core-java-22/src/main/java/com/baeldung/javafeatures/MainApp.java

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package com.baeldung.javafeatures;
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public class MainApp {
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public static void main(String[] args) {
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System.out.println("Hello");
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MultiFileExample mm = new MultiFileExample();
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mm.ping(args[0]);
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}
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}

‎core-java-modules/core-java-22/src/main/java/com/baeldung/javafeatures/MemoryAPIExample.java

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package com.baeldung.javafeatures;
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import static java.lang.foreign.FunctionDescriptor.*;
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import java.lang.foreign.Arena;
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import java.lang.foreign.FunctionDescriptor;
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import java.lang.foreign.Linker;
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import java.lang.foreign.MemorySegment;
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import java.lang.foreign.SymbolLookup;
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import java.lang.foreign.ValueLayout;
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import java.lang.invoke.MethodHandle;
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public class MemoryAPIExample {
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public long getLengthUsingNativeMethod(String string) throws Throwable {
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SymbolLookup stdlib = Linker.nativeLinker().defaultLookup();
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MethodHandle strlen =
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Linker.nativeLinker()
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.downcallHandle(
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stdlib.find("strlen").orElseThrow(),
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of(ValueLayout.JAVA_LONG, ValueLayout.ADDRESS));
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try (Arena offHeap = Arena.ofConfined()) {
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MemorySegment str = offHeap.allocateFrom(string);
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long len = (long) strlen.invoke(str);
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System.out.println("Finding String length using strlen function: " + len);
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return len;
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}
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}
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}

‎core-java-modules/core-java-22/src/main/java/com/baeldung/javafeatures/MultiFileExample.java

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package com.baeldung.javafeatures;
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public class MultiFileExample {
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public void ping(String s) {
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System.out.println("Ping from Second File " + s);
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}
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}

‎core-java-modules/core-java-22/src/main/java/com/baeldung/javafeatures/ScopedValueExample.java

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package com.baeldung.javafeatures;
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import java.util.Random;
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public class ScopedValueExample {
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public final static ScopedValue<User> LOGGED_IN_USER = ScopedValue.newInstance();
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public void serve(Request request) {
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User loggedInUser = authenticateUser(request);
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ScopedValue.where(LOGGED_IN_USER, loggedInUser)
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.run(() -> processRequest(request));
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}
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private User authenticateUser(Request request) {
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return new User(new Random().nextInt(100), STR."User\{new Random().nextInt()}");
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}
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private void processRequest(Request request) {
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System.out.println("Processing request :: " + ScopedValueExample.LOGGED_IN_USER.get()
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.toString());
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}
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}
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class User {
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private int id;
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private String userName;
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public User(int id, String userName) {
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this.id = id;
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this.userName = userName;
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}
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public String toString() {
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return STR."User :: \{this.id}";
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}
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}
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class Request {
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}

‎core-java-modules/core-java-22/src/main/java/com/baeldung/javafeatures/StreamGatherersExample.java

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package com.baeldung.javafeatures;
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import java.util.List;
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import java.util.stream.Gatherers;
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public class StreamGatherersExample {
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public List<List<String>> gatherIntoWindows(List<String> countries) {
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List<List<String>> windows = countries.stream()
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.gather(Gatherers.windowSliding(3))
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.toList();
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return windows;
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}
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}

‎core-java-modules/core-java-22/src/main/java/com/baeldung/javafeatures/UnnamedExpressions.java

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package com.baeldung.javafeatures;
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import static java.lang.StringTemplate.STR;
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import java.sql.Connection;
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import java.sql.DriverManager;
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import java.sql.SQLException;
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import java.util.ArrayList;
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import java.util.HashMap;
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import java.util.List;
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import java.util.Map;
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import java.util.logging.Logger;
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public class UnnamedExpressions {
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private Logger LOGGER = Logger.getLogger(String.valueOf(UnnamedExpressions.class));
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public int unnamedExpressionExampleUsingException(int someNumber) {
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int divided = 0;
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try {
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divided = someNumber / 0;
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} catch (ArithmeticException _) {
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System.err.println("Division by zero");
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}
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return divided;
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}
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public Object unnamedExpressionsExampleUsingSwitch(Object obj) {
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switch (obj) {
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case Integer _ -> System.out.println("Is an integer");
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case Float _ -> System.out.println("Is a float");
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case String _ -> System.out.println("Is a String");
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default -> System.out.println("Default");
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}
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;
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return obj;
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}
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public boolean unnamedExpressionForTryWithResources() {
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String url = "localhost";
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String user = "user";
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String pwd = "password";
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try (Connection _ = DriverManager.getConnection(url, user, pwd)) {
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LOGGER.info(STR."""
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DB Connection successful
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URL = \{url}
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usr = \{user}
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pwd = \{pwd}""");
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} catch (SQLException e) {
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LOGGER.warning("Exception");
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}
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return true;
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}
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public Map<String, List<String>> unnamedExpressionForLambda() {
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Map<String, List<String>> map = new HashMap<>();
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map.computeIfAbsent("v1", _ -> new ArrayList<>())
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.add("0.1");
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return map;
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}
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}
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‎core-java-modules/core-java-22/src/main/java/com/baeldung/javafeatures/classfile/ClassFileDriver.java

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package com.baeldung.javafeatures.classfile;
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import java.io.IOException;
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import java.lang.classfile.ClassElement;
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import java.lang.classfile.ClassFile;
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import java.lang.classfile.ClassModel;
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import java.lang.classfile.MethodModel;
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import java.nio.file.Files;
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import java.nio.file.Path;
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public class ClassFileDriver {
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public Path updateClass() throws IOException {
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final String PREFIX = "test_";
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final Path PATH = Path.of("src/main/java/com/baeldung/javafeatures/classfile/ClassFileExample.class");
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ClassFile cf = ClassFile.of();
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ClassModel classModel = cf.parse(PATH);
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byte[] newBytes = cf.build(classModel.thisClass().asSymbol(), classBuilder -> {
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for (ClassElement ce : classModel) {
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if (!(ce instanceof MethodModel mm && mm.methodName()
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.stringValue()
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.startsWith(PREFIX))) {
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classBuilder.with(ce);
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}
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}
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});
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return Files.write(PATH, newBytes);
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}
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}

‎core-java-modules/core-java-22/src/main/java/com/baeldung/javafeatures/classfile/ClassFileExample.java

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package com.baeldung.javafeatures.classfile;
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public class ClassFileExample {
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public void doSomething() {
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System.out.println("Do something here");
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}
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public void doSomething2() {
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System.out.println("Do something here as well");
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}
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public void test_something() {
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System.out.println("Test method");
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}
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}

‎core-java-modules/core-java-22/src/main/java/com/baeldung/javafeatures/shapes/Circle.java

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package com.baeldung.javafeatures.shapes;
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public class Circle extends Shape {
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int sides;
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int length;
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Circle(int sides, int length) {
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if (sides != 0 && length > 0) {
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throw new IllegalArgumentException("Cannot form circle");
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}
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super(sides, length);
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}
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@Override
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int getArea() {
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return (int) (this.length * this.length * 3.14);
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}
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}

‎core-java-modules/core-java-22/src/main/java/com/baeldung/javafeatures/shapes/Shape.java

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package com.baeldung.javafeatures.shapes;
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public abstract class Shape {
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private int sides;
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private int length;
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Shape(int sides, int length) {
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this.sides = sides;
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this.length = length;
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}
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abstract int getArea();
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}

‎core-java-modules/core-java-22/src/main/java/com/baeldung/javafeatures/shapes/Square.java

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package com.baeldung.javafeatures.shapes;
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public class Square extends Shape {
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int sides;
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int length;
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public Square(int sides, int length) {
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if (sides != 4 && length <= 0) {
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throw new IllegalArgumentException("Cannot form Square");
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}
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super(sides, length);
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}
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@Override
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int getArea() {
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return 4 * length;
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}
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public String whoAmI() {
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return "I am a square";
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}
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}

‎core-java-modules/core-java-22/src/test/java/com/baeldung/javafeatures/Java22ExamplesUnitTest.java

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package com.baeldung.javafeatures;
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import java.io.IOException;
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import java.util.List;
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import org.junit.Assert;
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import org.junit.Test;
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import com.baeldung.javafeatures.classfile.ClassFileDriver;
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public class Java22ExamplesUnitTest {
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@Test
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public void givenJava22_whenUsingLanguagePatterns_thenReturnResult() {
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UnnamedExpressions um = new UnnamedExpressions();
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Assert.assertEquals(0, um.unnamedExpressionExampleUsingException(100));
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Assert.assertEquals(123, um.unnamedExpressionsExampleUsingSwitch(123));
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Assert.assertTrue(um.unnamedExpressionForTryWithResources());
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Assert.assertNotNull(um.unnamedExpressionForLambda());
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}
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@Test
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public void givenJava22_whenUsingClassFileAPI_thenReturnUpdatedClass() throws IOException {
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ClassFileDriver classFileDriver = new ClassFileDriver();
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Assert.assertNotNull(classFileDriver.updateClass());
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}
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@Test
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public void givenJava22_whenUsingForeignAPI_thenReturnLengthUsingCFunction() throws Throwable {
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MemoryAPIExample mp = new MemoryAPIExample();
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Assert.assertEquals(11, mp.getLengthUsingNativeMethod("Hello world"));
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}
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@Test
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public void givenJava22_whenUsingStreamGatherer_thenReturnCustomList() {
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Assert.assertNotNull(new StreamGatherersExample().gatherIntoWindows(List.of("India", "Poland", "UK", "Australia", "USA", "Netherlands")));
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}
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}

‎core-java-modules/pom.xml

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<module>java-spi</module>
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<module>java-websocket</module>
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<module>core-java-8-datetime-3</module>
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<!--<module>core-java-22</module>--> <!-- requires JDK 22 -->
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</modules>
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<dependencies>

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