optimizations, more comfortable PromiseFactory api and support virtual threaded executors

futur-api/src/main/java/dev/tommyjs/futur/joiner/ResultJoiner.java

@@ -0,0 +1,56 @@
+package dev.tommyjs.futur.joiner;
+
+import dev.tommyjs.futur.promise.Promise;
+import dev.tommyjs.futur.promise.PromiseCompletion;
+import dev.tommyjs.futur.promise.PromiseFactory;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
+
+import java.util.Iterator;
+import java.util.List;
+import java.util.function.BiConsumer;
+
+public class ResultJoiner<T> extends PromiseJoiner<Promise<T>, Void, T, List<T>> {
+
+    private final @Nullable BiConsumer<Integer, Throwable> exceptionHandler;
+    private final ConcurrentResultArray<T> results;
+
+    public ResultJoiner(
+        @NotNull PromiseFactory factory,
+        @NotNull Iterator<Promise<T>> promises,
+        @Nullable BiConsumer<Integer, Throwable> exceptionHandler,
+        int expectedSize, boolean link
+    ) {
+        super(factory);
+        this.exceptionHandler = exceptionHandler;
+        this.results = new ConcurrentResultArray<>(expectedSize);
+        join(promises, link);
+    }
+
+    @Override
+    protected Void getKey(Promise<T> value) {
+        return null;
+    }
+
+    @Override
+    protected @NotNull Promise<T> getPromise(Promise<T> value) {
+        return value;
+    }
+
+    @Override
+    protected @Nullable Throwable onFinish(int index, Void key, @NotNull PromiseCompletion<T> res) {
+        if (res.isError()) {
+            if (exceptionHandler == null) return res.getException();
+            exceptionHandler.accept(index, res.getException());
+        }
+
+        results.set(index, res.getResult());
+        return null;
+    }
+
+    @Override
+    protected List<T> getResult() {
+        return results.toList();
+    }
+
+}