Make JavaIterator a Swift Iterator and Java list a Swift Sequence

We should generalize this to all of the various Java collection types.

Author: DougGregor

Sources/JavaKitCollection/JavaIterator+Iterator.swift

@@ -0,0 +1,27 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2024 Apple Inc. and the Swift.org project authors
+// Licensed under Apache License v2.0
+//
+// See LICENSE.txt for license information
+// See CONTRIBUTORS.txt for the list of Swift.org project authors
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+//===----------------------------------------------------------------------===//
+import JavaKit
+
+extension JavaIterator: IteratorProtocol {
+  public typealias Element = E
+
+  public func next() -> E? {
+    if hasNext() {
+      let nextResult: JavaObject? = next()
+      return nextResult.map { $0.as(E.self)! }
+    }
+
+    return nil
+  }
+}

Sources/JavaKitCollection/List+Sequence.swift

@@ -0,0 +1,23 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2024 Apple Inc. and the Swift.org project authors
+// Licensed under Apache License v2.0
+//
+// See LICENSE.txt for license information
+// See CONTRIBUTORS.txt for the list of Swift.org project authors
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+//===----------------------------------------------------------------------===//
+
+extension List: Sequence {
+  public typealias Element = E
+  public typealias Iterator = JavaIterator<E>
+
+  public func makeIterator() -> Iterator {
+    return self.iterator()!.as(JavaIterator<E>.self)!
+  }
+}
+