[java] CompletableFuture

README.md

@@ -14,6 +14,8 @@
 
 [设计模式](design-pattern/)
 
+[Java](java/)
+
 [机器学习](ML/)
 
 [Spring Boot](spring-boot-demo/)

java/.gitignore

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+.idea/
+target/
+.DS_Store

java/pom.xml

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+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+
+    <groupId>ml.sun</groupId>
+    <artifactId>demo</artifactId>
+    <version>1.0-SNAPSHOT</version>
+
+    <properties>
+        <maven.compiler.source>21</maven.compiler.source>
+        <maven.compiler.target>21</maven.compiler.target>
+        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
+        <!-- -->
+        <junit.version>5.11.0</junit.version>
+    </properties>
+
+    <dependencies>
+        <dependency>
+            <groupId>org.junit.jupiter</groupId>
+            <artifactId>junit-jupiter</artifactId>
+            <version>${junit.version}</version>
+            <scope>test</scope>
+        </dependency>
+    </dependencies>
+</project>

java/src/main/java/juc/MemberService.java

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+package juc;
+
+import java.util.Collections;
+import java.util.Map;
+
+public class MemberService {
+    public Map<?, ?> search() {
+        System.out.println("MemberService.search();");
+        try {
+            Thread.sleep(300);
+        } catch (InterruptedException e) {
+            throw new RuntimeException(e);
+        }
+        return Collections.emptyMap();
+    }
+}

java/src/main/java/juc/OrderService.java

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+package juc;
+
+import java.util.Collections;
+import java.util.List;
+
+public class OrderService {
+    public List<?> search() {
+        System.out.println("OrderService.search();");
+        try {
+            Thread.sleep(400);
+        } catch (InterruptedException e) {
+            throw new RuntimeException(e);
+        }
+        return Collections.emptyList();
+    }
+}

java/src/main/java/juc/ProductService.java

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+package juc;
+
+import java.util.Collections;
+import java.util.List;
+
+public class ProductService {
+    public List<?> search() {
+        System.out.println("ProductService.search();");
+        try {
+            Thread.sleep(500);
+        } catch (InterruptedException e) {
+            throw new RuntimeException(e);
+        }
+        return Collections.emptyList();
+    }
+}

java/src/main/java/juc/ServiceRunner.java

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+package juc;
+
+import java.util.List;
+import java.util.Map;
+import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.ExecutionException;
+
+public class ServiceRunner {
+    private static final MemberService MEMBER_SERVICE = new MemberService();
+    private static final OrderService ORDER_SERVICE = new OrderService();
+    private static final ProductService PRODUCT_SERVICE = new ProductService();
+
+    public static void sequence() {
+        MEMBER_SERVICE.search();
+        ORDER_SERVICE.search();
+        PRODUCT_SERVICE.search();
+    }
+
+    public static void parallel() {
+        CompletableFuture<?> member = CompletableFuture.supplyAsync(MEMBER_SERVICE::search);
+        CompletableFuture<?> order = CompletableFuture.supplyAsync(ORDER_SERVICE::search);
+        CompletableFuture<?> product = CompletableFuture.supplyAsync(PRODUCT_SERVICE::search);
+        CompletableFuture.allOf(member, order, product).join();
+        try {
+            member.get();
+            order.get();
+            product.get();
+        } catch (ExecutionException | InterruptedException e) {
+            throw new RuntimeException(e);
+        }
+    }
+
+    /**
+     * member
+     * / \
+     * order product
+     */
+    public static void preorder() {
+        CompletableFuture.completedFuture(MEMBER_SERVICE.search()).join();
+        //
+        CompletableFuture<?> order = CompletableFuture.supplyAsync(ORDER_SERVICE::search);
+        CompletableFuture<?> product = CompletableFuture.supplyAsync(PRODUCT_SERVICE::search);
+        CompletableFuture.allOf(order, product).join();
+    }
+
+    /**
+     * member
+     * product - order
+     */
+    public static void event() {
+        CompletableFuture<?> member = CompletableFuture.supplyAsync(MEMBER_SERVICE::search);
+        CompletableFuture<?> product = CompletableFuture.supplyAsync(PRODUCT_SERVICE::search);
+        CompletableFuture<?> order = product.thenApply((products) -> ORDER_SERVICE.search());
+        CompletableFuture.allOf(member, order).join();
+    }
+}

java/src/test/java/juc/ServiceRunnerTest.java

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+package juc;
+
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+
+public class ServiceRunnerTest {
+    @Test
+    public void test() {
+        Assertions.assertEquals(12, run("sequence", ServiceRunner::sequence) / 100);
+        Assertions.assertEquals(5, run("parallel", ServiceRunner::parallel) / 100);
+        Assertions.assertEquals(8, run("preorder", ServiceRunner::preorder) / 100);
+        Assertions.assertEquals(9, run("event", ServiceRunner::event) / 100);
+    }
+
+    public long run(String name, Runnable runnable) {
+        long startTime = System.currentTimeMillis();
+        runnable.run();
+        long endTime = System.currentTimeMillis();
+        long duration = endTime - startTime;
+        System.out.println(name + " total time: " + duration + "ms\n");
+        return duration;
+    }
+}