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mkyongmkyong
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java 19
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Lines changed: 290 additions & 9 deletions

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‎java-18/src/main/java/com/mkyong/java18/HelloApp.java‎

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‎java-19/pom.xml‎

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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
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http://maven.apache.org/xsd/maven-4.0.0.xsd">
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<modelVersion>4.0.0</modelVersion>
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<groupId>com.mkyong</groupId>
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<artifactId>java19</artifactId>
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<version>1.0</version>
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<name>java-19</name>
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<url>https://mkyong.com</url>
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<properties>
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<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
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<maven.compiler.source>19</maven.compiler.source>
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<maven.compiler.target>19</maven.compiler.target>
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<java.version>19</java.version>
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</properties>
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<dependencies>
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</dependencies>
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<build>
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<finalName>java19</finalName>
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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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<version>3.8.1</version>
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<configuration>
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<source>19</source>
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<target>19</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>

‎java-19/src/main/java/com/mkyong/java19/jep405/JEP405.java‎

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package com.mkyong.java19.jep405;
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public class JEP405 {
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record Point(int x, int y) {
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}
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static void printSum(Object o) {
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if (o instanceof Point p) {
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int x = p.x(); // get x()
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int y = p.y(); // get y()
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System.out.println(x + y);
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}
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}
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static void printSumNew(Object o) {
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if (o instanceof Point(int x,int y)) { // record pattern
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System.out.println(x + y);
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}
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}
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public static void main(String[] args) {
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printSumNew(new Point(10, 20)); // output 30
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}
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}

‎java-19/src/main/java/com/mkyong/java19/jep405/JEP405_1.java‎

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package com.mkyong.java19.jep405;
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public class JEP405_1 {
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record Point(int x, int y) {
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}
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record Total(Point p1, Point p2) {
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}
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static void printSum(Object o) {
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// record nested pattern
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if (o instanceof Total(Point(int x,int y),Point(int x2,int y2))) {
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System.out.println(x + y + x2 + y2);
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}
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}
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public static void main(String[] args) {
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printSum(new Total(new Point(10, 5), new Point(2, 3)));
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}
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}

‎java-19/src/main/java/com/mkyong/java19/jep424/JEP424_SORT.java‎

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package com.mkyong.java19.jep424;
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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.MemoryAddress;
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import java.lang.foreign.MemorySegment;
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import java.lang.foreign.SegmentAllocator;
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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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import static java.lang.foreign.ValueLayout.*;
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public class JEP424_SORT {
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public static void main(String[] args) throws Throwable {
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// 1. Find foreign function on the C library path
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Linker linker = Linker.nativeLinker();
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SymbolLookup stdlib = linker.defaultLookup();
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// 2. Allocate on-heap memory to store strings
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String[] javaStrings = {"d", "z", "b", "c", "a"};
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// 3. Allocate off-heap memory to store pointers
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SegmentAllocator allocator = SegmentAllocator.implicitAllocator();
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MemorySegment offHeap = allocator.allocateArray(ValueLayout.ADDRESS, javaStrings.length);
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// 4. Copy the strings from on-heap to off-heap
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for (int i = 0; i < javaStrings.length; i++) {
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// Allocate a string off-heap, then store a pointer to it
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MemorySegment cString = allocator.allocateUtf8String(javaStrings[i]);
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offHeap.setAtIndex(ValueLayout.ADDRESS, i, cString);
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}
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MethodHandle radixSort = linker.downcallHandle(
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stdlib.lookup("radixsort").orElseThrow(),
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FunctionDescriptor.ofVoid(ADDRESS, JAVA_INT, ADDRESS, JAVA_CHAR));
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// 5. Sort the off-heap data by calling the foreign function
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radixSort.invoke(offHeap, javaStrings.length, MemoryAddress.NULL, '\0');
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// 6. Copy the (reordered) strings from off-heap to on-heap
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for (int i = 0; i < javaStrings.length; i++) {
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MemoryAddress cStringPtr = offHeap.getAtIndex(ValueLayout.ADDRESS, i);
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javaStrings[i] = cStringPtr.getUtf8String(0);
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}
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//print sort result
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for (String javaString : javaStrings) {
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System.out.println(javaString);
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}
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}
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}

‎java-19/src/main/java/com/mkyong/java19/jep424/JEP424_STRLEN.java‎

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package com.mkyong.java19.jep424;
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import java.lang.foreign.*;
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import java.lang.invoke.MethodHandle;
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import static java.lang.foreign.ValueLayout.ADDRESS;
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import static java.lang.foreign.ValueLayout.JAVA_LONG;
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public class JEP424_STRLEN {
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public static void main(String[] args) throws Throwable {
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String input = "Hello World";
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// 1. Find foreign function on the C library path
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SymbolLookup stdlib = Linker.nativeLinker().defaultLookup();
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// 2. Get a handle to the "strlen" function in the C standard library
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MethodHandle methodHandle = Linker.nativeLinker().downcallHandle(
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stdlib.lookup("strlen").orElseThrow(),
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FunctionDescriptor.of(JAVA_LONG, ADDRESS));
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// 3. Allocate off-heap memory to store strings
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MemorySegment memorySegment = SegmentAllocator
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.implicitAllocator().allocateUtf8String(input);
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// 4. Runs the foreign function "strlen"
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long length = (long) methodHandle.invoke(memorySegment);
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System.out.println("length = " + length);
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}
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}

‎java-19/src/main/java/com/mkyong/java19/jep425/JEP425.java‎

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package com.mkyong.java19.jep425;
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import java.time.Duration;
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import java.util.concurrent.Executors;
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import java.util.stream.IntStream;
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public class JEP425 {
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public static void main(String[] args) {
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try (var executor = Executors.newVirtualThreadPerTaskExecutor()) {
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IntStream.range(0, 10_000).forEach(i -> {
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executor.submit(() -> {
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Thread.sleep(Duration.ofSeconds(1));
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return i;
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});
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});
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} // executor.close() is called implicitly, and waits
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/*try (var executor = Executors.newFixedThreadPool(20)) {
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IntStream.range(0, 10_000).forEach(i -> {
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executor.submit(() -> {
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Thread.sleep(Duration.ofSeconds(1));
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return i;
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});
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});
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}*/
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System.out.println("Done");
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}
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}

‎java-19/src/main/java/com/mkyong/java19/jep427/JEP427.java‎

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package com.mkyong.java19.jep427;
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public class JEP427 {
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public static void main(String[] args) {
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testJava19("mkyong");
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testJava19("mkyongmkyong");
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}
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/* Old guarded pattern
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static void test(Object o) {
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switch (o) {
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case String s && s.length() > 6 -> System.out.println("String's length longer than 10!");
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case String s -> System.out.println("String's length is " + s.length());
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default -> {
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}
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}
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}*/
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//Guarded patterns are replaced with when clauses in switch blocks.
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static void testJava19(Object o) {
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switch (o) {
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case String s
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when s.length() > 10 -> System.out.println("String's length longer than 10!");
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case String s -> System.out.println("String's length is " + s.length());
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default -> {}
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}
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}
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}

‎java-19/src/main/java/com/mkyong/java19/jep428/JEP428.java‎

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package com.mkyong.java19.jep428;
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import java.time.Duration;
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import java.util.concurrent.ExecutionException;
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import java.util.concurrent.Executors;
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import java.util.concurrent.Future;
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public class JEP428 {
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public static void main(String[] args) throws ExecutionException, InterruptedException {
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JEP428 obj = new JEP428();
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obj.handleUnStructureAPI();
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}
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Response handleUnStructureAPI() throws ExecutionException, InterruptedException {
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try (var executor = Executors.newFixedThreadPool(10)) {
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Future<String> user = executor.submit(this::findUser);
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Future<Integer> order = executor.submit(this::fetchOrder);
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String theUser = user.get(); // Join findUser
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int theOrder = order.get(); // Join fetchOrder
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return new Response(theUser, theOrder);
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}
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}
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/*Response handleStructureAPI() throws ExecutionException, InterruptedException {
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try (var scope = new StructuredTaskScope.ShutdownOnFailure()) {
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Future<String> user = scope.fork(this::findUser);
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Future<Integer> order = scope.fork(this::fetchOrder);
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scope.join(); // Join both forks
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scope.throwIfFailed(); // ... and propagate errors
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// Here, both forks have succeeded, so compose their results
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return new Response(user.resultNow(), order.resultNow());
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}
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}*/
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private String findUser() throws InterruptedException {
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Thread.sleep(Duration.ofSeconds(1));
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return "mkyong";
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}
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private Integer fetchOrder() throws InterruptedException {
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Thread.sleep(Duration.ofSeconds(1));
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return 1;
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}
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record Response(String x, int y) {
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}
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}

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