Log warning message for unsupported action with Java

src/Cli/func/Actions/LocalActions/CreateFunctionAction.cs

@@ -309,6 +309,13 @@ public async Task UpdateLanguageAndRuntime()
                     throw new CliException("Selected language doesn't match worker set in local.settings.json." +
                         $"Selected worker is: {_workerRuntime} and selected language is: {workerRuntimeSelected}");
                 }
+
+                if (workerRuntimeSelected == WorkerRuntime.Java)
+                {
+                    ColoredConsole
+                        .WriteLine($"This action is not supported when using the core tools directly. Please use one of the supported environments to test {workerRuntimeSelected} apps locally as specified by" +
+                        $"https://learn.microsoft.com/en-us/azure/azure-functions/functions-develop-local?pivots=programming-language-java");
+                }
             }
             else if (string.IsNullOrWhiteSpace(Language))
             {

test/Cli/Func.UnitTests/ActionsTests/CreateFunctionActionTests.cs

@@ -0,0 +1,62 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the MIT License. See LICENSE in the project root for license information.
+
+using Azure.Functions.Cli.Actions.LocalActions;
+using Azure.Functions.Cli.Helpers;
+using Azure.Functions.Cli.Interfaces;
+using Moq;
+using Xunit;
+
+namespace Azure.Functions.Cli.UnitTests.ActionsTests
+{
+    public class CreateFunctionActionTests
+    {
+        [Fact]
+        public async Task UpdateLanguageAndRuntime_ThrowsCliException_ForJavaWorkerRuntime()
+        {
+            // Arrange
+            var templatesManager = new Mock<ITemplatesManager>();
+            var secretsManager = new Mock<ISecretsManager>();
+            var contextHelpManager = new Mock<IContextHelpManager>();
+            var action = new CreateFunctionAction(templatesManager.Object, secretsManager.Object, contextHelpManager.Object)
+            {
+                Language = "java"
+            };
+
+            // Set the current worker runtime to Java, mocking the behavior where func init has already been run
+            GlobalCoreToolsSettings.CurrentWorkerRuntime = WorkerRuntime.Java;
+
+            // Ensure local.settings.json exists in the current directory
+            var localSettingsPath = Path.Combine(Environment.CurrentDirectory, "local.settings.json");
+            File.WriteAllText(localSettingsPath, "{}"); // Write a minimal valid JSON
+
+            // Simulate worker runtime is Java
+            typeof(CreateFunctionAction)
+                .GetField("_workerRuntime", System.Reflection.BindingFlags.NonPublic | System.Reflection.BindingFlags.Instance)
+                .SetValue(action, WorkerRuntime.Java);
+
+            var stringWriter = new StringWriter();
+            var originalOut = Console.Out;
+            Console.SetOut(stringWriter);
+
+            try
+            {
+                // make sure no error is thrown
+                await action.UpdateLanguageAndRuntime();
+
+                // Assert
+                var output = stringWriter.ToString();
+                Assert.Contains("This action is not supported", output);
+                Assert.Contains("Java", output);
+            }
+            finally
+            {
+                Console.SetOut(originalOut);
+                if (File.Exists(localSettingsPath))
+                {
+                    File.Delete(localSettingsPath);
+                }
+            }
+        }
+    }
+}