diff --git a/.github/workflows/ci.yaml b/.github/workflows/ci.yaml
index f6279504..37ca6345 100644
--- a/.github/workflows/ci.yaml
+++ b/.github/workflows/ci.yaml
@@ -7,7 +7,7 @@ jobs:
   test:
     # https://docs.github.com/en/actions/using-workflows/workflow-syntax-for-github-actions#choosing-github-hosted-runners
     runs-on: ubuntu-latest
-    timeout-minutes: 10
+    timeout-minutes: 15
     name: CI by multiply java versions
 
     steps:
@@ -26,7 +26,6 @@ jobs:
             21
             22
           distribution: zulu
-          # only first java setup need enable cache
           cache: maven
 
       - name: Run integration test
diff --git a/.github/workflows/fast_ci.yaml b/.github/workflows/fast_ci.yaml
index 6ee48d24..bb046d3a 100644
--- a/.github/workflows/fast_ci.yaml
+++ b/.github/workflows/fast_ci.yaml
@@ -23,24 +23,6 @@ jobs:
         with:
           java-version: 21
           distribution: microsoft
-          # only first java setup need enable cache
           cache: maven
       - name: Build and test with Java 21
         run: ./mvnw -V --no-transfer-progress clean install
-
-      - name: Setup Java 8
-        uses: actions/setup-java@v4
-        with:
-          java-version: 8
-          distribution: zulu
-      - name: Test with Java 8
-        run: ./mvnw -V --no-transfer-progress surefire:test
-
-      - name: 'Remove self maven install files(OS: *nix)'
-        run: rm -rf $HOME/.m2/repository/io/foldright/cffu*
-        # https://docs.github.com/en/actions/learn-github-actions/expressions
-        # https://docs.github.com/en/actions/learn-github-actions/variables#detecting-the-operating-system
-        if: runner.os != 'Windows'
-      - name: 'Remove self maven install files(OS: Windows)'
-        run: Remove-Item -Recurse -Force $home/.m2/repository/io/foldright/cffu*
-        if: runner.os == 'Windows'
diff --git a/cffu-core/src/main/java/io/foldright/cffu/CffuFactory.java b/cffu-core/src/main/java/io/foldright/cffu/CffuFactory.java
index dbcd53d2..d7050fee 100644
--- a/cffu-core/src/main/java/io/foldright/cffu/CffuFactory.java
+++ b/cffu-core/src/main/java/io/foldright/cffu/CffuFactory.java
@@ -33,7 +33,6 @@
  * About factory methods conventions of {@link CffuFactory}:
  * <ul>
  *   <li>factory methods return {@link Cffu} instead of {@link CompletableFuture}.
- *   <li>new methods, aka. no equivalent method in {@link CompletableFuture}, prefix method name with {@code cffu}.
  *   <li>only provide varargs methods for multiply Cffu/CF input arguments;
  *     if you have {@code List} input, use static util methods {@link #cffuListToArray(List)}
  *     or {@link #completableFutureListToArray(List)} to convert it to array first.
@@ -293,11 +292,11 @@ public final <T> Cffu<T>[] asCffuArray(CompletionStage<T>... stages) {
     }
 
     ////////////////////////////////////////////////////////////////////////////////
-    //# allOf / anyOf methods, without return result type enhancement
+    //# allOf / anyOf methods
     //  - allOf*, return Cffu<Void>, equivalent to same name methods:
     //    - CompletableFuture.allOf()
     //    - CompletableFutureUtils.allOfFastFail()
-    //  - anyOf*, return Cffu<Object>, equivalent to same name methods:
+    //  - anyOf*, equivalent to same name methods:
     //    - CompletableFuture.anyOf()
     //    - CompletableFutureUtils.anyOfSuccess()
     ////////////////////////////////////////////////////////////////////////////////
@@ -567,10 +566,7 @@ public Executor delayedExecutor(long delay, TimeUnit unit, Executor executor) {
     }
 
     ////////////////////////////////////////////////////////////////////////////////
-    //# New type-safe allOf/anyOf Factory Methods
-    //    method name prefix with `cffu`
-    //
-    //    - allResultsOf
+    //# New allResultsOf* Factory Methods
     ////////////////////////////////////////////////////////////////////////////////
 
     /**
diff --git a/cffu-core/src/test/java/io/foldright/showcases/CompletableFutureUsageShowcaseTest.kt b/cffu-core/src/test/java/io/foldright/showcases/CompletableFutureUsageShowcaseTest.kt
index 2aaf749d..145c0b7a 100644
--- a/cffu-core/src/test/java/io/foldright/showcases/CompletableFutureUsageShowcaseTest.kt
+++ b/cffu-core/src/test/java/io/foldright/showcases/CompletableFutureUsageShowcaseTest.kt
@@ -1,5 +1,3 @@
-@file:OptIn(ExperimentalTime::class)
-
 package io.foldright.showcases
 
 import io.foldright.test_utils.*
@@ -18,7 +16,6 @@ import java.lang.System.currentTimeMillis
 import java.lang.Thread.currentThread
 import java.util.concurrent.*
 import java.util.concurrent.atomic.AtomicBoolean
-import kotlin.time.ExperimentalTime
 
 class CompletableFutureUsageShowcaseTest : FunSpec({
     val n = 42
diff --git a/cffu-kotlin/src/main/java/io/foldright/cffu/kotlin/CffuExtensions.kt b/cffu-kotlin/src/main/java/io/foldright/cffu/kotlin/CffuExtensions.kt
index 678fab42..d0bff955 100644
--- a/cffu-kotlin/src/main/java/io/foldright/cffu/kotlin/CffuExtensions.kt
+++ b/cffu-kotlin/src/main/java/io/foldright/cffu/kotlin/CffuExtensions.kt
@@ -50,10 +50,10 @@ fun <T> Array<out CompletionStage<T>>.asCffu(cffuFactory: CffuFactory): Array<Cf
 ////////////////////////////////////////
 // allOf* methods
 //
+//   - allResultsOfCffu
 //   - allOfCffu
-//   - allOfCffuVoid
+//   - allResultsOfFastFailCffu
 //   - allOfFastFailCffu
-//   - allOfFastFailCffuVoid
 ////////////////////////////////////////
 
 /**
@@ -384,9 +384,7 @@ fun Array<out CompletableFuture<*>>.allOfFastFailCffu(cffuFactory: CffuFactory):
 // anyOf* methods
 //
 //   - anyOfCffu
-//   - anyOfCffuAny
 //   - anyOfSuccessCffu
-//   - anyOfSuccessCffuAny
 ////////////////////////////////////////
 
 /**
diff --git a/cffu-kotlin/src/main/java/io/foldright/cffu/kotlin/CompletableFutureExtensions.kt b/cffu-kotlin/src/main/java/io/foldright/cffu/kotlin/CompletableFutureExtensions.kt
index 5ed95679..c9ae9c5f 100644
--- a/cffu-kotlin/src/main/java/io/foldright/cffu/kotlin/CompletableFutureExtensions.kt
+++ b/cffu-kotlin/src/main/java/io/foldright/cffu/kotlin/CompletableFutureExtensions.kt
@@ -1,3 +1,5 @@
+@file:Suppress("EXTENSION_SHADOWED_BY_MEMBER")
+
 package io.foldright.cffu.kotlin
 
 import io.foldright.cffu.CffuState
@@ -10,6 +12,8 @@ import java.util.concurrent.CompletableFuture
 import java.util.concurrent.CompletionStage
 import java.util.concurrent.Executor
 import java.util.concurrent.TimeUnit
+import java.util.function.Function
+import java.util.function.Supplier
 
 
 ////////////////////////////////////////////////////////////////////////////////
@@ -383,8 +387,6 @@ fun <T1, T2, T3, T4, T5> CompletableFuture<T1>.combineFastFail(
 ////////////////////////////////////////////////////////////////////////////////
 //# Backport CF instance methods
 //  compatibility for low Java version
-//
-//  all methods name prefix with `cffu`
 ////////////////////////////////////////////////////////////////////////////////
 
 //# Error Handling methods of CompletionStage
@@ -399,7 +401,7 @@ fun <T1, T2, T3, T4, T5> CompletableFuture<T1>.combineFastFail(
  * if given CompletionStage completed exceptionally
  * @return the new CompletionStage
  */
-fun <T> CompletableFuture<T>.cffuExceptionallyAsync(fn: (Throwable) -> T): CompletableFuture<T> =
+fun <T> CompletableFuture<T>.exceptionallyAsync(fn: Function<Throwable, out T>): CompletableFuture<T> =
     CompletableFutureUtils.exceptionallyAsync(this, fn)
 
 /**
@@ -412,20 +414,22 @@ fun <T> CompletableFuture<T>.cffuExceptionallyAsync(fn: (Throwable) -> T): Compl
  * @param executor the executor to use for asynchronous execution
  * @return the new CompletionStage
  */
-fun <T> CompletableFuture<T>.cffuExceptionallyAsync(fn: (Throwable) -> T, executor: Executor): CompletableFuture<T> =
+fun <T> CompletableFuture<T>.exceptionallyAsync(
+    fn: Function<Throwable, out T>, executor: Executor
+): CompletableFuture<T> =
     CompletableFutureUtils.exceptionallyAsync(this, fn, executor)
 
 //# Timeout Control methods
 
 /**
- * Exceptionally completes this CompletableFuture with a [TimeoutException][java.util.concurrent.TimeoutException]
+ * Exceptionally completes this CompletableFuture with a TimeoutException
  * if not otherwise completed before the given timeout.
  *
  * @param timeout how long to wait before completing exceptionally with a TimeoutException, in units of `unit`
  * @param unit    a `TimeUnit` determining how to interpret the `timeout` parameter
  * @return this CompletableFuture
  */
-fun <T> CompletableFuture<T>.cffuOrTimeout(timeout: Long, unit: TimeUnit): CompletableFuture<T> =
+fun <T> CompletableFuture<T>.orTimeout(timeout: Long, unit: TimeUnit): CompletableFuture<T> =
     CompletableFutureUtils.orTimeout(this, timeout, unit)
 
 /**
@@ -436,7 +440,7 @@ fun <T> CompletableFuture<T>.cffuOrTimeout(timeout: Long, unit: TimeUnit): Compl
  * @param unit    a `TimeUnit` determining how to interpret the `timeout` parameter
  * @return given CompletableFuture
  */
-fun <T> CompletableFuture<T>.cffuCompleteOnTimeout(value: T, timeout: Long, unit: TimeUnit): CompletableFuture<T> =
+fun <T> CompletableFuture<T>.completeOnTimeout(value: T, timeout: Long, unit: TimeUnit): CompletableFuture<T> =
     CompletableFutureUtils.completeOnTimeout(this, value, timeout, unit)
 
 //# Advanced methods of CompletionStage
@@ -449,7 +453,9 @@ fun <T> CompletableFuture<T>.cffuCompleteOnTimeout(value: T, timeout: Long, unit
  *           CompletionStage if given CompletionStage completed exceptionally
  * @return the new CompletionStage
  */
-fun <T> CompletableFuture<T>.cffuExceptionallyCompose(fn: (Throwable) -> CompletionStage<T>): CompletableFuture<T> =
+fun <T> CompletableFuture<T>.exceptionallyCompose(
+    fn: Function<Throwable, out CompletionStage<T>>
+): CompletableFuture<T> =
     CompletableFutureUtils.exceptionallyCompose(this, fn)
 
 /**
@@ -461,8 +467,8 @@ fun <T> CompletableFuture<T>.cffuExceptionallyCompose(fn: (Throwable) -> Complet
  *           CompletionStage if given CompletionStage completed exceptionally
  * @return the new CompletionStage
  */
-fun <T> CompletableFuture<T>.cffuExceptionallyComposeAsync(
-    fn: (Throwable) -> CompletionStage<T>
+fun <T> CompletableFuture<T>.exceptionallyComposeAsync(
+    fn: Function<Throwable, out CompletionStage<T>>
 ): CompletableFuture<T> =
     CompletableFutureUtils.exceptionallyComposeAsync(this, fn)
 
@@ -475,8 +481,8 @@ fun <T> CompletableFuture<T>.cffuExceptionallyComposeAsync(
  * @param executor the executor to use for asynchronous execution
  * @return the new CompletionStage
  */
-fun <T> CompletableFuture<T>.cffuExceptionallyComposeAsync(
-    fn: (Throwable) -> CompletionStage<T>, executor: Executor
+fun <T> CompletableFuture<T>.exceptionallyComposeAsync(
+    fn: Function<Throwable, out CompletionStage<T>>, executor: Executor
 ): CompletableFuture<T> =
     CompletableFutureUtils.exceptionallyComposeAsync(this, fn, executor)
 
@@ -501,9 +507,8 @@ fun <T> CompletableFuture<T>.cffuExceptionallyComposeAsync(
  * ```
  *
  * <b><i>CAUTION:<br></i></b>
- * if the wait timed out, this method throws an (unchecked) [CompletionException][java.util.concurrent.CompletionException]
- * with the [TimeoutException][java.util.concurrent.TimeoutException] as its cause;
- * NOT throws a (checked) [TimeoutException][java.util.concurrent.TimeoutException] like [CompletableFuture.get].
+ * if the wait timed out, this method throws an (unchecked) CompletionException with the TimeoutException as its cause;
+ * NOT throws a (checked) TimeoutException like [CompletableFuture.get].
  *
  * @param timeout the maximum time to wait
  * @param unit    the time unit of the timeout argument
@@ -530,7 +535,7 @@ fun <T> CompletableFuture<T>.join(timeout: Long, unit: TimeUnit): T =
  * ```
  */
 @Suppress("UNCHECKED_CAST")
-fun <T> CompletableFuture<T>.cffuResultNow(): T =
+fun <T> CompletableFuture<T>.resultNow(): T =
     CompletableFutureUtils.resultNow(this) as T
 
 /**
@@ -543,7 +548,7 @@ fun <T> CompletableFuture<T>.cffuResultNow(): T =
  *                               or the task was cancelled
  * @see CompletableFuture#resultNow()
  */
-fun <T> CompletableFuture<T>.cffuExceptionNow(): Throwable =
+fun <T> CompletableFuture<T>.exceptionNow(): Throwable =
     CompletableFutureUtils.exceptionNow(this)
 
 /**
@@ -566,7 +571,7 @@ fun <T> CompletableFuture<T>.cffuState(): CffuState =
  * @param supplier a function returning the value to be used to complete given CompletableFuture
  * @return given CompletableFuture
  */
-fun <T> CompletableFuture<T>.cffuCompleteAsync(supplier: () -> T): CompletableFuture<T> =
+fun <T> CompletableFuture<T>.completeAsync(supplier: Supplier<out T>): CompletableFuture<T> =
     CompletableFutureUtils.completeAsync(this, supplier)
 
 /**
@@ -577,7 +582,7 @@ fun <T> CompletableFuture<T>.cffuCompleteAsync(supplier: () -> T): CompletableFu
  * @param executor the executor to use for asynchronous execution
  * @return given CompletableFuture
  */
-fun <T> CompletableFuture<T>.cffuCompleteAsync(supplier: () -> T, executor: Executor): CompletableFuture<T> =
+fun <T> CompletableFuture<T>.completeAsync(supplier: Supplier<out T>, executor: Executor): CompletableFuture<T> =
     CompletableFutureUtils.completeAsync(this, supplier, executor)
 
 //# Re-Config methods
@@ -594,7 +599,7 @@ fun <T> CompletableFuture<T>.cffuCompleteAsync(supplier: () -> T, executor: Exec
  *
  * @return the new CompletionStage
  */
-fun <T> CompletableFuture<T>.cffuMinimalCompletionStage(): CompletionStage<T> =
+fun <T> CompletableFuture<T>.minimalCompletionStage(): CompletionStage<T> =
     CompletableFutureUtils.minimalCompletionStage(this)
 
 /**
@@ -606,7 +611,7 @@ fun <T> CompletableFuture<T>.cffuMinimalCompletionStage(): CompletionStage<T> =
  *
  * @return the new CompletableFuture
  */
-fun <T> CompletableFuture<T>.cffuCopy(): CompletableFuture<T> =
+fun <T> CompletableFuture<T>.copy(): CompletableFuture<T> =
     CompletableFutureUtils.copy(this)
 
 /**
@@ -615,5 +620,5 @@ fun <T> CompletableFuture<T>.cffuCopy(): CompletableFuture<T> =
  * @param <T> the type of the value
  * @return a new CompletableFuture
  */
-fun <T, U> CompletableFuture<T>.cffuNewIncompleteFuture(): CompletableFuture<U> =
+fun <T, U> CompletableFuture<T>.newIncompleteFuture(): CompletableFuture<U> =
     CompletableFutureUtils.newIncompleteFuture(this)
diff --git a/cffu-kotlin/src/test/java/io/foldright/cffu/test/CompletableFutureExtensionsTest.kt b/cffu-kotlin/src/test/java/io/foldright/cffu/test/CompletableFutureExtensionsTest.kt
index f99fcb5d..95ac14fa 100644
--- a/cffu-kotlin/src/test/java/io/foldright/cffu/test/CompletableFutureExtensionsTest.kt
+++ b/cffu-kotlin/src/test/java/io/foldright/cffu/test/CompletableFutureExtensionsTest.kt
@@ -264,61 +264,59 @@ class CompletableFutureExtensionsTest : FunSpec({
     ////////////////////////////////////////////////////////////////////////////////
     //# Backport CF instance methods
     //  compatibility for low Java version
-    //
-    //  all methods name prefix with `cffu`
     ////////////////////////////////////////////////////////////////////////////////
 
     test("exceptionallyAsync") {
         val cf = CompletableFutureUtils.failedFuture<Int>(rte)
-        cf.cffuExceptionallyAsync { n }.get() shouldBe n
-        cf.cffuExceptionallyAsync({ n }, testThreadPoolExecutor).get() shouldBe n
+        cf.exceptionallyAsync { n }.get() shouldBe n
+        cf.exceptionallyAsync({ n }, testThreadPoolExecutor).get() shouldBe n
     }
 
-    test(" test_timeout") {
+    test("test_timeout") {
         var cf = CompletableFuture<Int>()
         shouldThrow<ExecutionException> {
-            cf.cffuOrTimeout(1, TimeUnit.MILLISECONDS).get()
+            cf.orTimeout(1, TimeUnit.MILLISECONDS).get()
         }.cause.shouldBeTypeOf<TimeoutException>()
 
         cf = CompletableFuture()
-        cf.cffuCompleteOnTimeout(n, 1, TimeUnit.MILLISECONDS).get() shouldBe n
+        cf.completeOnTimeout(n, 1, TimeUnit.MILLISECONDS).get() shouldBe n
     }
 
     test("exceptionallyCompose") {
         val cf = CompletableFutureUtils.failedFuture<Int>(rte)
-        cf.cffuExceptionallyCompose { CompletableFuture.completedFuture(n) }.get() shouldBe n
-        cf.cffuExceptionallyComposeAsync { CompletableFuture.completedFuture(n) }.get() shouldBe n
-        cf.cffuExceptionallyComposeAsync({ CompletableFuture.completedFuture(n) }, testThreadPoolExecutor)
+        cf.exceptionallyCompose { CompletableFuture.completedFuture(n) }.get() shouldBe n
+        cf.exceptionallyComposeAsync { CompletableFuture.completedFuture(n) }.get() shouldBe n
+        cf.exceptionallyComposeAsync({ CompletableFuture.completedFuture(n) }, testThreadPoolExecutor)
             .get() shouldBe n
     }
 
-    test("read") {
+    test("read methods") {
         val cf = CompletableFuture.completedFuture(n)
         val ff = CompletableFutureUtils.failedFuture<Int>(rte)
 
         cf.join(1, TimeUnit.MILLISECONDS) shouldBe n
-        cf.cffuResultNow() shouldBe n
-        ff.cffuExceptionNow() shouldBeSameInstanceAs rte
+        cf.resultNow() shouldBe n
+        ff.exceptionNow() shouldBeSameInstanceAs rte
 
         cf.cffuState() shouldBe CffuState.SUCCESS
         ff.cffuState() shouldBe CffuState.FAILED
     }
 
-    test("write") {
+    test("write methods") {
         val cf = CompletableFuture<Int>()
-        cf.cffuCompleteAsync { n }.get() shouldBe n
-        cf.cffuCompleteAsync({ n }, testThreadPoolExecutor).get() shouldBe n
+        cf.completeAsync { n }.get() shouldBe n
+        cf.completeAsync({ n }, testThreadPoolExecutor).get() shouldBe n
     }
 
     test("re_config") {
-        CompletableFuture.completedFuture(n).cffuMinimalCompletionStage()
+        CompletableFuture.completedFuture(n).minimalCompletionStage()
             .toCompletableFuture().get() shouldBe n
 
         val cf = CompletableFuture<Int>()
-        cf.cffuCopy().complete(n)
+        cf.copy().complete(n)
         cf.isDone.shouldBeFalse()
 
-        val incomplete = cf.cffuNewIncompleteFuture<Int, Any>()
+        val incomplete: CompletableFuture<Int> = cf.newIncompleteFuture()
         incomplete.isDone.shouldBeFalse()
         incomplete.complete(n)
         cf.isDone.shouldBeFalse()
diff --git a/scripts/integration_test b/scripts/integration_test
index e0b15d73..a37f6e65 100755
--- a/scripts/integration_test
+++ b/scripts/integration_test
@@ -74,5 +74,44 @@ for jdk_version in "${JDK_VERSIONS[@]}"; do
 
   kt_version_var_name="KT_VERSION_FOR_JAVA${jdk_version}"
   kt_version_opt="${!kt_version_var_name:+-Dkotlin.version=${!kt_version_var_name}}"
-  mvu::mvn_cmd ${CI_MORE_BEGIN_OPTS:-} dependency:properties surefire:test ${CI_MORE_END_OPTS:-} $kt_version_opt
+
+  pl=
+  if ((jdk_version < default_build_jdk_version)); then
+    pl='-pl cffu-core,cffu-ttl-executor-wrapper'
+  fi
+
+  mvu::mvn_cmd ${pl:-} ${CI_MORE_BEGIN_OPTS:-} dependency:properties surefire:test ${CI_MORE_END_OPTS:-} $kt_version_opt
+done
+
+# test the kotlin extension methods works
+#
+# CAUTION: MUST re-compile the client sources(test codes) by Java 8
+#   Extensions are resolved statically.
+#   If a class has a member function, and an extension function is defined
+#     which has the same receiver type, the same name, and is applicable to given arguments,
+#   the member always wins
+#   https://kotlinlang.org/docs/extensions.html#extensions-are-resolved-statically
+
+jvu::switch_to_jdk 8
+
+cd cffu-kotlin
+
+# recompile cffu-kotlin and run test
+rm -rf target/*test*
+cu::head_line_echo "recompile and test cffu-kotlin with Java 8: $JAVA_HOME"
+mvu::mvn_cmd -P'!gen-git-properties' -Dmaven.main.skip -Denforcer.skip ${CI_MORE_BEGIN_OPTS:-} dependency:properties test-compile surefire:test ${CI_MORE_END_OPTS:-}
+
+for jdk_version in "${JDK_VERSIONS[@]}"; do
+  # skip default jdk, already tested above
+  ((jdk_version == 8)) && continue
+
+  jvu::switch_to_jdk "$jdk_version"
+
+  # just test without build
+  cu::head_line_echo "test cffu-kotlin with Java $jdk_version: $JAVA_HOME"
+
+  kt_version_var_name="KT_VERSION_FOR_JAVA${jdk_version}"
+  kt_version_opt="${!kt_version_var_name:+-Dkotlin.version=${!kt_version_var_name}}"
+
+  mvu::mvn_cmd -Dmaven.main.skip -Denforcer.skip ${CI_MORE_BEGIN_OPTS:-} dependency:properties surefire:test ${CI_MORE_END_OPTS:-} $kt_version_opt
 done