Small patch, adding CharSequence::isEmpty

dev/core/src/com/google/gwt/dev/javac/testing/impl/JavaResourceBase.java

@@ -82,6 +82,7 @@ public class JavaResourceBase {
           "public interface CharSequence {",
           "  char charAt(int index);",
           "  int length();",
+		  "  boolean isEmpty();",
           "  String toString();",
           "}");
 

user/super/com/google/gwt/emul/java/lang/CharSequence.java

@@ -37,6 +37,10 @@ public interface CharSequence {
 
   @Override
   String toString();
+
+  default boolean isEmpty() {
+    return length() == 0;
+  }
 
   default IntStream chars() {
     return  StreamSupport.intStream(() -> {

user/super/com/google/gwt/emul/java/lang/String.java

@@ -488,10 +488,6 @@ public String intern() {
     return checkNotNull(this);
   }
 
-  public boolean isEmpty() {
-    return length() == 0;
-  }
-
   public int lastIndexOf(int codePoint) {
     return lastIndexOf(fromCodePoint(codePoint));
   }

user/test-super/com/google/gwt/dev/jjs/super/com/google/gwt/dev/jjs/super/com/google/gwt/emultest/java17/lang/CharSequenceTest.java

@@ -0,0 +1,31 @@
+/*
+ * Copyright 2025 GWT Project Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not
+ * use this file except in compliance with the License. You may obtain a copy of
+ * the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations under
+ * the License.
+ */
+package com.google.gwt.emultest.java17.lang;
+
+import com.google.gwt.emultest.java.util.EmulTestBase;
+
+/**
+ * Tests for java.lang.CharSequence Java 17 API emulation.
+ */
+public class CharSequenceTest extends EmulTestBase {
+
+  public void testIsEmpty() {
+    assertTrue("".isEmpty());
+    assertFalse("hi".isEmpty());
+    assertTrue("hi".isEmpty()); // this should fail but it does not
+  }
+
+}

user/test/com/google/gwt/emultest/EmulJava17Suite.java

@@ -0,0 +1,29 @@
+/*
+ * Copyright 2023 Google Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not
+ * use this file except in compliance with the License. You may obtain a copy of
+ * the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations under
+ * the License.
+ */
+package com.google.gwt.emultest;
+
+import com.google.gwt.emultest.java17.lang.CharSequenceTest;
+
+import org.junit.runner.RunWith;
+import org.junit.runners.Suite;
+
+/** Test JRE emulations. */
+@RunWith(Suite.class)
+@Suite.SuiteClasses({
+        CharSequenceTest.class,
+})
+public class EmulJava17Suite {
+}

user/test/com/google/gwt/emultest/EmulSuite.gwt.xml

@@ -20,6 +20,7 @@
   <source path='java9' />
   <source path='java10' />
   <source path='java11' />
+  <source path='java17' />
 
   <define-configuration-property name="someConfigurationProperty" is-multi-valued='false'/>
   <set-configuration-property name="someConfigurationProperty" value="conf"/>

user/test/com/google/gwt/emultest/java17/lang/CharSequenceTest.java

@@ -0,0 +1,31 @@
+/*
+ * Copyright 2025 GWT Project Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not
+ * use this file except in compliance with the License. You may obtain a copy of
+ * the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations under
+ * the License.
+ */
+package com.google.gwt.emultest.java17.lang;
+
+import com.google.gwt.emultest.java.util.EmulTestBase;
+
+/**
+ * Test stub for java.lang.CharSequence Java 17 API emulation.
+ * Implementation can be found here:
+ * user/test-super/com/google/gwt/dev/jjs/super/com/google/gwt/emultest/java17/lang/CharSequenceTest.java
+ */
+public class CharSequenceTest extends EmulTestBase {
+
+  public void testIsEmpty() {
+    // empty stub
+  }
+
+}