add: increase download concurrency. According to https://www.bilibili.com/video/av89055581.

HMCL/src/main/java/org/jackhuang/hmcl/setting/DownloadProviders.java

@@ -23,9 +23,12 @@ import javafx.beans.value.ObservableObjectValue;
 import org.jackhuang.hmcl.download.BMCLAPIDownloadProvider;
 import org.jackhuang.hmcl.download.DownloadProvider;
 import org.jackhuang.hmcl.download.MojangDownloadProvider;
+import org.jackhuang.hmcl.task.Schedulers;
+import org.jackhuang.hmcl.ui.FXUtils;
 
 import java.util.Map;
 import java.util.Optional;
+import java.util.concurrent.ThreadPoolExecutor;
 
 import static org.jackhuang.hmcl.setting.ConfigHolder.config;
 import static org.jackhuang.hmcl.util.Lang.mapOf;
@@ -48,6 +51,10 @@ public final class DownloadProviders {
                 () -> Optional.ofNullable(providersById.get(config().getDownloadType()))
                         .orElse(providersById.get(DEFAULT_PROVIDER_ID)),
                 config().downloadTypeProperty());
+
+        FXUtils.onChangeAndOperate(downloadProviderProperty, provider -> {
+            Schedulers.io().setMaximumPoolSize(provider.getConcurrency());
+        });
     }
 
     public static DownloadProvider getDownloadProvider() {

HMCLCore/src/main/java/org/jackhuang/hmcl/download/BMCLAPIDownloadProvider.java

@@ -90,4 +90,8 @@ public class BMCLAPIDownloadProvider implements DownloadProvider {
                 .replace("https://authlib-injector.yushi.moe", apiRoot + "/mirrors/authlib-injector");
     }
 
+    @Override
+    public int getConcurrency() {
+        return Math.max(Runtime.getRuntime().availableProcessors() * 2, 6);
+    }
 }

HMCLCore/src/main/java/org/jackhuang/hmcl/download/DownloadProvider.java

@@ -56,4 +56,10 @@ public interface DownloadProvider {
      * @throws IllegalArgumentException if the version list does not exist
      */
     VersionList<?> getVersionListById(String id);
+
+    /**
+     * The maximum download concurrency that this download provider supports.
+     * @return the maximum download concurrency.
+     */
+    int getConcurrency();
 }

HMCLCore/src/main/java/org/jackhuang/hmcl/download/MojangDownloadProvider.java

@@ -76,4 +76,9 @@ public class MojangDownloadProvider implements DownloadProvider {
     public String injectURL(String baseURL) {
         return baseURL;
     }
+
+    @Override
+    public int getConcurrency() {
+        return 6;
+    }
 }

HMCLCore/src/main/java/org/jackhuang/hmcl/task/Schedulers.java

@@ -22,16 +22,7 @@ import org.jackhuang.hmcl.util.Logging;
 import org.jetbrains.annotations.NotNull;
 
 import javax.swing.*;
-import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.*;
-import java.util.concurrent.ExecutionException;
-import java.util.concurrent.Executor;
-import java.util.concurrent.ExecutorService;
-import java.util.concurrent.Executors;
-import java.util.concurrent.Future;
-import java.util.concurrent.SynchronousQueue;
-import java.util.concurrent.ThreadPoolExecutor;
-import java.util.concurrent.TimeUnit;
-import java.util.concurrent.TimeoutException;
 import java.util.concurrent.atomic.AtomicReference;
 
 /**
@@ -43,9 +34,9 @@ public final class Schedulers {
     private Schedulers() {
     }
 
-    private static volatile ExecutorService CACHED_EXECUTOR;
+    private static volatile ThreadPoolExecutor CACHED_EXECUTOR;
 
-    public static synchronized Executor newThread() {
+    public static synchronized ThreadPoolExecutor newThread() {
         if (CACHED_EXECUTOR == null)
             CACHED_EXECUTOR = new ThreadPoolExecutor(0, Integer.MAX_VALUE,
                     60, TimeUnit.SECONDS, new SynchronousQueue<>(), Executors.defaultThreadFactory());
@@ -53,22 +44,25 @@ public final class Schedulers {
         return CACHED_EXECUTOR;
     }
 
-    private static volatile ExecutorService IO_EXECUTOR;
+    private static volatile ThreadPoolExecutor IO_EXECUTOR;
 
-    public static synchronized Executor io() {
+    public static synchronized ThreadPoolExecutor io() {
         if (IO_EXECUTOR == null)
-            IO_EXECUTOR = Executors.newFixedThreadPool(6, runnable -> {
+            IO_EXECUTOR = new ThreadPoolExecutor(0, 6,
-                Thread thread = Executors.defaultThreadFactory().newThread(runnable);
+                    60L, TimeUnit.SECONDS,
-                thread.setDaemon(true);
+                    new SynchronousQueue<>(),
-                return thread;
+                    runnable -> {
-            });
+                        Thread thread = Executors.defaultThreadFactory().newThread(runnable);
+                        thread.setDaemon(true);
+                        return thread;
+                    });
 
         return IO_EXECUTOR;
     }
 
     private static volatile ExecutorService SINGLE_EXECUTOR;
 
-    public static synchronized Executor computation() {
+    public static synchronized ExecutorService computation() {
         if (SINGLE_EXECUTOR == null)
             SINGLE_EXECUTOR = Executors.newSingleThreadExecutor(runnable -> {
                 Thread thread = Executors.defaultThreadFactory().newThread(runnable);