Added: ExecutorService and CompletableFuture examples

Author: nilandev

src/com/stacktips/threads/WebScraper.java

@@ -1,19 +1,31 @@
 package com.stacktips.threads;
 
 import java.io.IOException;
-import java.net.URL;
+import java.net.URI;
+import java.net.URISyntaxException;
+import java.net.http.HttpClient;
+import java.net.http.HttpRequest;
+import java.net.http.HttpResponse;
 
 public class WebScraper {
 
     String scrapeWebsite(String urlString) {
-        try {
-            URL url = new URL(urlString);
-            try (var stream = url.openStream()) {
-                int contentLength = stream.readAllBytes().length;
-                return String.format("URL: %s, Content Length: %d bytes", urlString, contentLength);
-            }
+        try (HttpClient client = HttpClient.newHttpClient()) {
+            HttpRequest request = HttpRequest.newBuilder()
+                    .uri(new URI(urlString))
+                    .build();
+            HttpResponse<String> response = client.send(request, HttpResponse.BodyHandlers.ofString());
+
+            return String.format("URL: %s, Content Length: %d bytes", urlString, response.body().length());
+
+        } catch (URISyntaxException e) {
+            System.out.println("URI Syntax Exception: " + e.getMessage());
         } catch (IOException e) {
-            return "Error scraping " + urlString + ": " + e.getMessage();
+            System.out.println("URI Syntax Exception: " + e.getMessage());
+        } catch (InterruptedException e) {
+            System.out.println("URI Syntax Exception: " + e.getMessage());
         }
+
+        return "Error: Unable to scrape website.";
     }
 }

src/com/stacktips/threads/WebScraperUsingCompletableFuture.java

@@ -1,7 +1,10 @@
 package com.stacktips.threads;
 
 import java.util.List;
-import java.util.concurrent.*;
+import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.TimeUnit;
 
 public class WebScraperUsingCompletableFuture {
 
@@ -15,18 +18,16 @@ public WebScraperUsingCompletableFuture(int nThreads) {
 
     public List<String> scrapeWebsites(List<String> urls) {
         List<CompletableFuture<String>> futures = urls.stream()
-            .map(url -> CompletableFuture.supplyAsync(() -> webScraper.scrapeWebsite(url), executorService)
-                .orTimeout(30, TimeUnit.SECONDS)
-                .exceptionally(e -> "Error: " + e.getMessage()))
-            .toList();
+                .map(url -> CompletableFuture.supplyAsync(() -> webScraper.scrapeWebsite(url), executorService)
+                        .orTimeout(30, TimeUnit.SECONDS)
+                        .exceptionally(e -> "Error: " + e.getMessage()))
+                .toList();
 
         return futures.stream()
-            .map(CompletableFuture::join)
-            .toList();
+                .map(CompletableFuture::join)
+                .toList();
     }
 
-
-
     public void shutdown() {
         executorService.shutdown();
         try {
@@ -40,11 +41,11 @@ public void shutdown() {
 
     public static void main(String[] args) {
         List<String> urls = List.of(
-            "https://www.example.com",
-            "https://www.github.com",
-            "https://www.stackoverflow.com",
-            "https://www.java.com",
-            "https://www.spring.io"
+                "https://www.example.com",
+                "https://www.github.com",
+                "https://www.stackoverflow.com",
+                "https://www.java.com",
+                "https://www.spring.io"
         );
 
         WebScraperUsingCompletableFuture scraper = new WebScraperUsingCompletableFuture(3);