jextract: Support Java DoubleConsumer func interface

Samples/SwiftAndJavaJarFFMSampleLib/Sources/MySwiftLibrary/MySwiftLibrary.swift

@@ -60,6 +60,10 @@ public func globalCallMeLongConsumer(run: (Int64) -> Void) {
   run(1)
 }
 
+public func globalCallMeDoubleConsumer(run: (Double) -> Void) {
+  run(1.0)
+}
+
 // ==== Internal helpers
 
 func p(_ msg: String, file: String = #fileID, line: UInt = #line, function: String = #function) {

Samples/SwiftAndJavaJarFFMSampleLib/src/test/java/com/example/swift/MySwiftLibraryTest.java

@@ -87,4 +87,9 @@ void call_globalCallMeIntConsumer_noThrow() {
     void call_globalCallMeLongConsumer_noThrow() {
         MySwiftLibrary.globalCallMeLongConsumer((long a) -> { });
     }
+
+    @Test
+    void call_globalCallMeDoubleConsumer_noThrow() {
+        MySwiftLibrary.globalCallMeDoubleConsumer((double a) -> { });
+    }
 }

Samples/SwiftJavaExtractFFMSampleApp/Sources/MySwiftLibrary/MySwiftLibrary.swift

@@ -72,6 +72,10 @@ public func globalCallMeLongConsumer(run: (Int64) -> Void) {
   run(1)
 }
 
+public func globalCallMeDoubleConsumer(run: (Double) -> Void) {
+  run(1.0)
+}
+
 public func globalReceiveRawBuffer(buf: UnsafeRawBufferPointer) -> Int {
   buf.count
 }

Samples/SwiftJavaExtractFFMSampleApp/src/test/java/com/example/swift/MySwiftLibraryTest.java

@@ -199,4 +199,9 @@ void call_globalCallMeIntConsumer_noThrow() {
     void call_globalCallMeLongConsumer_noThrow() {
         MySwiftLibrary.globalCallMeLongConsumer((long a) -> { });
     }
+
+    @Test
+    void call_globalCallMeDoubleConsumer_noThrow() {
+        MySwiftLibrary.globalCallMeDoubleConsumer((double a) -> { });
+    }
 }

Samples/SwiftJavaExtractJNISampleApp/Sources/MySwiftLibrary/Closures.swift

@@ -45,6 +45,10 @@ public func globalCallMeLongConsumer(run: (Int64) -> Void) {
   run(1)
 }
 
+public func globalCallMeDoubleConsumer(run: (Double) -> Void) {
+  run(1.0)
+}
+
 public func closureMultipleArguments(
   input1: Int64,
   input2: Int64,

Samples/SwiftJavaExtractJNISampleApp/src/test/java/com/example/swift/ClosuresTest.java

@@ -81,4 +81,9 @@ void globalCallMeIntConsumer() {
     void globalCallMeLongConsumer() {
         MySwiftLibrary.globalCallMeLongConsumer((long a) -> {});
     }
+
+    @Test
+    void globalCallMeDoubleConsumer() {
+        MySwiftLibrary.globalCallMeDoubleConsumer((double a) -> {});
+    }
 }

Sources/ExampleSwiftLibrary/MySwiftLibrary.swift

@@ -67,6 +67,10 @@ public func globalCallMeLongConsumer(run: (Int64) -> Void) {
   run(1)
 }
 
+public func globalCallMeDoubleConsumer(run: (Double) -> Void) {
+  run(1.0)
+}
+
 public func globalReceiveRawBuffer(buf: UnsafeRawBufferPointer) -> Int {
   buf.count
 }

Sources/JExtractSwiftLib/JavaTypes/JavaType+JDK.swift

@@ -60,6 +60,11 @@ extension JavaType {
     .class(package: "java.util.function", name: "LongConsumer")
   }
 
+  /// The description of the type java.util.function.DoubleConsumer.
+  static var javaUtilFunctionDoubleConsumer: JavaType {
+    .class(package: "java.util.function", name: "DoubleConsumer")
+  }
+
   /// The description of the type java.lang.Class.
   static var javaLangClass: JavaType {
     .class(package: "java.lang", name: "Class")

Sources/JExtractSwiftLib/KnownFunctionalInterfaces.swift

@@ -2,7 +2,7 @@
 //
 // This source file is part of the Swift.org open source project
 //
-// Copyright (c) 2025 Apple Inc. and the Swift.org project authors
+// Copyright (c) 2026 Apple Inc. and the Swift.org project authors
 // Licensed under Apache License v2.0
 //
 // See LICENSE.txt for license information
@@ -71,6 +71,13 @@ struct KnownJavaFunctionalInterface: Sendable {
     result: .void
   )
 
+  static let doubleConsumer = KnownJavaFunctionalInterface(
+    JavaType.javaUtilFunctionDoubleConsumer,
+    method: "accept",
+    parameters: [.double],
+    result: .void
+  )
+
   static let all: [KnownJavaFunctionalInterface] = [
     .runnable,
     .booleanSupplier,
@@ -79,6 +86,7 @@ struct KnownJavaFunctionalInterface: Sendable {
     .doubleSupplier,
     .intConsumer,
     .longConsumer,
+    .doubleConsumer,
   ]
 
   static func find(parameters: [JavaType], result: JavaType) -> KnownJavaFunctionalInterface? {
@@ -131,6 +139,8 @@ struct KnownJavaFunctionalInterface: Sendable {
         intConsumer
       case _ where parameter.isInt64:
         longConsumer
+      case _ where parameter.isDouble:
+        doubleConsumer
       default:
         nil
       }

Tests/JExtractSwiftTests/FuncCallbackImportTests.swift

@@ -41,6 +41,7 @@ final class FuncCallbackImportTests {
 
     public func callMeIntConsumer(callback: (Int32) -> Void)
     public func callMeLongConsumer(callback: (Int64) -> Void)
+    public func callMeDoubleConsumer(callback: (Double) -> Void)
 
     public func callMeMore(callback: (UnsafeRawPointer, Float) -> Int, fn: () -> ())
     public func withBuffer(body: (UnsafeRawBufferPointer) -> Int)
@@ -431,6 +432,49 @@ final class FuncCallbackImportTests {
     )
   }
 
+  @Test("Import: public func callMeDoubleConsumerFunc(callback: (Double) -> Void)")
+  func func_callMeDoubleConsumerFunc_callback() throws {
+    var config = Configuration()
+    config.swiftModule = "__FakeModule"
+    let st = makeSwiftJavaAnalyzer(config: config)
+    st.log.logLevel = .error
+
+    try st.analyze(path: "Fake.swift", text: Self.class_interfaceFile)
+
+    let funcDecl = st.extractedGlobalFuncs.first { $0.name == "callMeDoubleConsumer" }!
+
+    let generator = FFMSwift2JavaGenerator(
+      config: config,
+      translator: st,
+      javaPackage: "com.example.swift",
+      swiftOutputDirectory: "/fake",
+      javaOutputDirectory: "/fake"
+    )
+
+    let output = JavaPrinter.toString { printer in
+      generator.printFunctionDowncallMethods(&printer, funcDecl)
+    }
+
+    assertOutput(
+      output,
+      expectedChunks: [
+        """
+        /**
+         * Downcall to Swift:
+         * {@snippet lang=swift :
+         * public func callMeDoubleConsumer(callback: (Double) -> Void)
+         * }
+         */
+        public static void callMeDoubleConsumer(java.util.function.DoubleConsumer callback) {
+          try(var arena$ = Arena.ofConfined()) {
+            swiftjava___FakeModule_callMeDoubleConsumer_callback.call(callMeDoubleConsumer.$toUpcallStub(callback, arena$));
+          }
+        }
+        """
+      ]
+    )
+  }
+
   @Test("Import: public func callMeMore(callback: (UnsafeRawPointer, Float) -> Int, fn: () -> ())")
   func func_callMeMoreFunc_callback() throws {
     var config = Configuration()

Tests/JExtractSwiftTests/JNI/JNIClosureTests.swift

@@ -27,6 +27,7 @@ struct JNIClosureTests {
 
     public func closureIntConsumer(closure: (Int32) -> Void) {}
     public func closureLongConsumer(closure: (Int64) -> Void) {}
+    public func closureDoubleConsumer(closure: (Double) -> Void) {}
 
     public func closureWithArgumentsAndReturn(closure: (Int64, Bool) -> Int64) {}
     """
@@ -206,6 +207,31 @@ struct JNIClosureTests {
     )
   }
 
+  @Test
+  func closureDoubleConsumer_javaBindings() throws {
+    try assertOutput(
+      input: source,
+      .jni,
+      .java,
+      expectedChunks: [
+        """
+        /**
+         * Downcall to Swift:
+         * {@snippet lang=swift :
+         * public func closureDoubleConsumer(closure: (Double) -> Void)
+         * }
+         */
+        public static void closureDoubleConsumer(java.util.function.DoubleConsumer closure) {
+          SwiftModule.$closureDoubleConsumer(closure);
+        }
+        """,
+        """
+        private static native void $closureDoubleConsumer(java.util.function.DoubleConsumer closure);
+        """,
+      ]
+    )
+  }
+
   @Test
   func emptyClosure_swiftThunks() throws {
     try assertOutput(
@@ -381,6 +407,31 @@ struct JNIClosureTests {
     )
   }
 
+  @Test
+  func closureDoubleConsumer_swiftThunks() throws {
+    try assertOutput(
+      input: source,
+      .jni,
+      .swift,
+      detectChunkByInitialLines: 1,
+      expectedChunks: [
+        """
+        @_cdecl("Java_com_example_swift_SwiftModule__00024closureDoubleConsumer__Ljava_util_function_DoubleConsumer_2")
+        public func Java_com_example_swift_SwiftModule__00024closureDoubleConsumer__Ljava_util_function_DoubleConsumer_2(environment: UnsafeMutablePointer<JNIEnv?>!, thisClass: jclass, closure: jobject?) {
+          SwiftModule.closureDoubleConsumer(closure: {
+            let class$ = environment.interface.GetObjectClass(environment, closure)
+            let methodID$ = environment.interface.GetMethodID(environment, class$, "accept", "(D)V")!
+            environment.interface.DeleteLocalRef(environment, class$)
+            let arguments$: [jvalue] = [_0.getJValue(in: environment)]
+            environment.interface.CallVoidMethodA(environment, closure, methodID$, arguments$)
+          }
+          )
+        }
+        """
+      ]
+    )
+  }
+
   @Test
   func closureWithArgumentsAndReturn_javaBindings() throws {
     try assertOutput(