add toFuture method

futur-api/src/main/java/dev/tommyjs/futur/promise/AbstractPromise.java

@@ -10,10 +10,7 @@ import org.jetbrains.annotations.Nullable;
 import org.slf4j.Logger;
 
 import java.util.Collection;
-import java.util.concurrent.CancellationException;
+import java.util.concurrent.*;
-import java.util.concurrent.ConcurrentLinkedQueue;
-import java.util.concurrent.TimeUnit;
-import java.util.concurrent.TimeoutException;
 import java.util.concurrent.atomic.AtomicReference;
 import java.util.function.Consumer;
 
@@ -438,4 +435,16 @@ public abstract class AbstractPromise<T, F> implements Promise<T> {
         return completion.get();
     }
 
+    @Override
+    public @NotNull CompletableFuture<T> toFuture() {
+        CompletableFuture<T> future = new CompletableFuture<>();
+        this.addDirectListener(future::complete, future::completeExceptionally);
+        future.whenComplete((res, e) -> {
+            if (e instanceof CancellationException) {
+                this.cancel();
+            }
+        });
+        return future;
+    }
+
 }

futur-api/src/main/java/dev/tommyjs/futur/promise/Promise.java

@@ -8,6 +8,7 @@ import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 
 import java.util.concurrent.CancellationException;
+import java.util.concurrent.CompletableFuture;
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.TimeoutException;
 import java.util.concurrent.atomic.AtomicReference;
@@ -128,4 +129,6 @@ public interface Promise<T> {
 
     boolean isCompleted();
 
+    @NotNull CompletableFuture<T> toFuture();
+
 }

futur-api/src/test/java/dev/tommyjs/futur/PromiseTests.java

@@ -48,6 +48,21 @@ public final class PromiseTests {
         assert !finished.get();
     }
 
+    @Test
+    public void testToFuture() throws InterruptedException {
+        assert pfac.resolve(true).toFuture().getNow(false);
+        assert pfac.error(new Exception("Test")).toFuture().isCompletedExceptionally();
+
+        var finished = new AtomicBoolean();
+        pfac.start()
+            .thenRunDelayedAsync(() -> finished.set(true), 50, TimeUnit.MILLISECONDS)
+            .toFuture()
+            .cancel(true);
+
+        Thread.sleep(100L);
+        assert !finished.get();
+    }
+
     @Test
     public void testCombineUtil() throws TimeoutException {
         pfac.all(