diff --git a/dev/codeserver/javatests/com/google/gwt/dev/codeserver/RecompilerTest.java b/dev/codeserver/javatests/com/google/gwt/dev/codeserver/RecompilerTest.java
index 03abc05fd71..33a8830c5d2 100644
--- a/dev/codeserver/javatests/com/google/gwt/dev/codeserver/RecompilerTest.java
+++ b/dev/codeserver/javatests/com/google/gwt/dev/codeserver/RecompilerTest.java
@@ -28,13 +28,13 @@
 import com.google.gwt.thirdparty.guava.common.base.Charsets;
 import com.google.gwt.thirdparty.guava.common.collect.ImmutableMap;
 import com.google.gwt.thirdparty.guava.common.collect.Lists;
-import com.google.gwt.thirdparty.guava.common.io.Files;
 
 import junit.framework.TestCase;
 
 import java.io.File;
 import java.io.FilenameFilter;
 import java.io.IOException;
+import java.nio.file.Files;
 import java.util.Arrays;
 import java.util.Comparator;
 import java.util.HashMap;
@@ -68,7 +68,7 @@ private static void writeResourcesTo(List<MockResource> resources, File dir) thr
       File resourceFile =
           new File(dir.getAbsolutePath() + File.separator + applicationResource.getPath());
       resourceFile.getParentFile().mkdirs();
-      Files.write(applicationResource.getContent(), resourceFile, Charsets.UTF_8);
+      Files.write(resourceFile.toPath(), List.of(applicationResource.getContent()), Charsets.UTF_8);
     }
   }
 
@@ -163,7 +163,7 @@ public void testIncrementalRecompile_compileErrorDoesntCorruptMinimalRebuildCach
     PrintWriterTreeLogger logger = new PrintWriterTreeLogger();
     logger.setMaxDetail(TreeLogger.ERROR);
 
-    File sourcePath = Files.createTempDir();
+    File sourcePath = createTempDir();
     // Setup options to perform a per-file compile and compile the given module.
     Options options = new Options();
     options.parseArgs(new String[] {
@@ -175,12 +175,12 @@ public void testIncrementalRecompile_compileErrorDoesntCorruptMinimalRebuildCach
         fooResource);
     writeResourcesTo(originalResources, sourcePath);
 
-    File baseCacheDir = Files.createTempDir();
+    File baseCacheDir = createTempDir();
     UnitCache unitCache = UnitCacheSingleton.get(
         logger, null, baseCacheDir, new CompilerOptionsImpl(options));
     MinimalRebuildCacheManager minimalRebuildCacheManager =
         new MinimalRebuildCacheManager(logger, baseCacheDir, ImmutableMap.<String, String>of());
-    Recompiler recompiler = new Recompiler(OutboxDir.create(Files.createTempDir(), logger), null,
+    Recompiler recompiler = new Recompiler(OutboxDir.create(createTempDir(), logger), null,
         moduleName, options, unitCache, minimalRebuildCacheManager);
     Outbox outbox = new Outbox("Transactional Cache", recompiler, options, logger);
     OutboxTable outboxTable = new OutboxTable();
@@ -211,7 +211,7 @@ public void testIncrementalRecompile_modulePropertyEditsWork() throws UnableToCo
     PrintWriterTreeLogger logger = new PrintWriterTreeLogger();
     logger.setMaxDetail(TreeLogger.ERROR);
 
-    File sourcePath = Files.createTempDir();
+    File sourcePath = createTempDir();
     // Setup options to perform a per-file compile and compile the given module.
     Options options = new Options();
     options.parseArgs(new String[] {
@@ -223,12 +223,12 @@ public void testIncrementalRecompile_modulePropertyEditsWork() throws UnableToCo
         fooResource);
     writeResourcesTo(originalResources, sourcePath);
 
-    File baseCacheDir = Files.createTempDir();
+    File baseCacheDir = createTempDir();
     UnitCache unitCache = UnitCacheSingleton.get(
         logger, null, baseCacheDir, new CompilerOptionsImpl(options));
     MinimalRebuildCacheManager minimalRebuildCacheManager =
         new MinimalRebuildCacheManager(logger, baseCacheDir, ImmutableMap.<String, String>of());
-    Recompiler recompiler = new Recompiler(OutboxDir.create(Files.createTempDir(), logger), null,
+    Recompiler recompiler = new Recompiler(OutboxDir.create(createTempDir(), logger), null,
         moduleName, options, unitCache, minimalRebuildCacheManager);
     Outbox outbox = new Outbox("Transactional Cache", recompiler, options, logger);
     OutboxTable outboxTable = new OutboxTable();
@@ -276,4 +276,8 @@ private Result compileWithChanges(TreeLogger logger, JobRunner runner, Outbox ou
     runner.submit(job);
     return job.waitForResult();
   }
+
+  private static File createTempDir() throws IOException {
+    return Files.createTempDirectory("RecompilerTest").toFile();
+  }
 }
diff --git a/dev/core/test/com/google/gwt/dev/CompilerTest.java b/dev/core/test/com/google/gwt/dev/CompilerTest.java
index 57e32447d9a..1161e3aac0a 100644
--- a/dev/core/test/com/google/gwt/dev/CompilerTest.java
+++ b/dev/core/test/com/google/gwt/dev/CompilerTest.java
@@ -37,10 +37,10 @@
 import com.google.gwt.thirdparty.guava.common.collect.ImmutableList;
 import com.google.gwt.thirdparty.guava.common.collect.Lists;
 import com.google.gwt.thirdparty.guava.common.collect.Sets;
-import com.google.gwt.thirdparty.guava.common.io.Files;
 
 import java.io.File;
 import java.io.IOException;
+import java.nio.file.Files;
 import java.util.Arrays;
 import java.util.HashSet;
 import java.util.List;
@@ -976,7 +976,7 @@ public void testSourceLevelHighestVersion() {
    */
   public void testGwtCreateJsTypeRebindResult() throws Exception {
     CompilerOptions compilerOptions = new CompilerOptionsImpl();
-    compileToJs(compilerOptions, Files.createTempDir(), "com.foo.SimpleModule",
+    compileToJs(compilerOptions, createTempDir(), "com.foo.SimpleModule",
         Lists.newArrayList(simpleModuleResource, gwtCreateEntryPointResource),
         new MinimalRebuildCache(), emptySet, JsOutputOption.OBFUSCATED);
   }
@@ -1032,7 +1032,7 @@ public void testReferenceThroughJsFunction() throws Exception {
             "</module>");
 
     CompilerOptions compilerOptions = new CompilerOptionsImpl();
-    String js = compileToJs(compilerOptions, Files.createTempDir(), testEntryPoint.getTypeName(),
+    String js = compileToJs(compilerOptions, createTempDir(), testEntryPoint.getTypeName(),
         Lists.newArrayList(moduleResource, testEntryPoint, someJsFunction,
             jsFunctionInterfaceImplementation, someInterface),
         new MinimalRebuildCache(), emptySet, JsOutputOption.DETAILED);
@@ -1340,7 +1340,7 @@ public void testChangeJsIgnore() throws Exception {
 
   public void testJsInteropNameCollision() throws Exception {
     MinimalRebuildCache minimalRebuildCache = new MinimalRebuildCache();
-    File applicationDir = Files.createTempDir();
+    File applicationDir = Files.createTempDirectory("JsInteropNameCollision").toFile();
     CompilerOptions compilerOptions = new CompilerOptionsImpl();
     compilerOptions.setGenerateJsInteropExports(true);
 
@@ -1368,7 +1368,7 @@ Lists.<MockResource> newArrayList(complexDialogResourceWithExport), minimalRebui
 
   public void testGwtCreateJsoRebindResult() throws Exception {
     try {
-      compileToJs(Files.createTempDir(), "com.foo.SimpleModule",
+      compileToJs(createTempDir(), "com.foo.SimpleModule",
           Lists.newArrayList(simpleModuleResource, brokenGwtCreateEntryPointResource),
           new MinimalRebuildCache(), emptySet, JsOutputOption.OBFUSCATED);
       fail("Compile should have failed");
@@ -1399,7 +1399,7 @@ public void testNonZeroArgConstructorEntryPoint() throws Exception {
             "}");
 
     MinimalRebuildCache minimalRebuildCache = new MinimalRebuildCache();
-    File applicationDir = Files.createTempDir();
+    File applicationDir = createTempDir();
     CompilerOptions compilerOptions = new CompilerOptionsImpl();
 
     UnitTestTreeLogger.Builder builder = new UnitTestTreeLogger.Builder();
@@ -1546,7 +1546,7 @@ public void testIncrementalRecompile_jsPropertyConsistencyCheck()
             "</module>");
 
     MinimalRebuildCache relinkMinimalRebuildCache = new MinimalRebuildCache();
-    File relinkApplicationDir = Files.createTempDir();
+    File relinkApplicationDir = createTempDir();
 
     // Perform a first compile.
     compileToJs(relinkApplicationDir, "com.foo.TestModule",
@@ -1565,7 +1565,7 @@ public void testIncrementalRecompile_jsPropertyConsistencyCheck()
   public void testIncrementalRecompile_invalidatePreamble() throws UnableToCompleteException,
       IOException, InterruptedException {
     MinimalRebuildCache relinkMinimalRebuildCache = new MinimalRebuildCache();
-    File relinkApplicationDir = Files.createTempDir();
+    File relinkApplicationDir = createTempDir();
 
     // Perform a first compile.
     compileToJs(relinkApplicationDir, "com.foo.SimpleModule",
@@ -1593,7 +1593,7 @@ Lists.<MockResource> newArrayList(emptyEntryPointResource), relinkMinimalRebuild
   public void testIncrementalRecompile_bridgeMethodOverrideChain()
       throws UnableToCompleteException, IOException, InterruptedException {
     MinimalRebuildCache relinkMinimalRebuildCache = new MinimalRebuildCache();
-    File relinkApplicationDir = Files.createTempDir();
+    File relinkApplicationDir = createTempDir();
 
     // Perform a first compile.
     compileToJs(relinkApplicationDir, "com.foo.SimpleModule", Lists.newArrayList(
@@ -1699,7 +1699,7 @@ public void testIncrementalRecompile_withErrors()
             "}");
 
     MinimalRebuildCache minimalRebuildCache = new MinimalRebuildCache();
-    File applicationDir = Files.createTempDir();
+    File applicationDir = createTempDir();
     CompilerOptions compilerOptions = new CompilerOptionsImpl();
     compilerOptions.setUseDetailedTypeIds(true);
     compilerOptions.setSourceLevel(SourceLevel.JAVA11);
@@ -1762,7 +1762,7 @@ public void testIncrementalRecompile_representedAsNative()
     logger.setMaxDetail(TreeLogger.ERROR);
 
     MinimalRebuildCache minimalRebuildCache = new MinimalRebuildCache();
-    File applicationDir = Files.createTempDir();
+    File applicationDir = createTempDir();
     CompilerOptions compilerOptions = new CompilerOptionsImpl();
     compilerOptions.setUseDetailedTypeIds(true);
     compilerOptions.setSourceLevel(SourceLevel.JAVA11);
@@ -1920,7 +1920,7 @@ public void testIncrementalRecompile_invalidatedGeneratorOutputRerunsGenerator()
 
     // Compile the app with original files, modify a file and do a per-file recompile.
     MinimalRebuildCache relinkMinimalRebuildCache = new MinimalRebuildCache();
-    File relinkApplicationDir = Files.createTempDir();
+    File relinkApplicationDir = createTempDir();
     compileToJs(compilerOptions, relinkApplicationDir, "com.foo.SimpleModule", originalResources,
         relinkMinimalRebuildCache, emptySet, output);
 
@@ -1960,7 +1960,7 @@ public void testIncrementalRecompile_invalidatedGeneratorOutputRerunsCascadedGen
 
     // Compile the app with original files.
     MinimalRebuildCache relinkMinimalRebuildCache = new MinimalRebuildCache();
-    File relinkApplicationDir = Files.createTempDir();
+    File relinkApplicationDir = createTempDir();
     compileToJs(compilerOptions, relinkApplicationDir, "com.foo.SimpleModule", originalResources,
         relinkMinimalRebuildCache, emptySet, output);
 
@@ -2009,7 +2009,7 @@ public void testIncrementalRecompile_carriesOverGeneratorArtifacts()
 
     // Compile the app with original files.
     MinimalRebuildCache relinkMinimalRebuildCache = new MinimalRebuildCache();
-    File relinkApplicationDir = Files.createTempDir();
+    File relinkApplicationDir = createTempDir();
     compileToJs(compilerOptions, relinkApplicationDir, "com.foo.SimpleModule", originalResources,
         relinkMinimalRebuildCache, emptySet, output);
 
@@ -2046,7 +2046,7 @@ public void testIncrementalRecompile_unifyASTAssertionRegression()
 
     // Compile the app with original files.
     MinimalRebuildCache relinkMinimalRebuildCache = new MinimalRebuildCache();
-    File relinkApplicationDir = Files.createTempDir();
+    File relinkApplicationDir = createTempDir();
     compileToJs(compilerOptions, relinkApplicationDir, "com.foo.Hello",
         originalResources, relinkMinimalRebuildCache, emptySet, output);
   }
@@ -2054,7 +2054,7 @@ public void testIncrementalRecompile_unifyASTAssertionRegression()
   private void checkIncrementalRecompile_noop(JsOutputOption output) throws UnableToCompleteException,
       IOException, InterruptedException {
     MinimalRebuildCache relinkMinimalRebuildCache = new MinimalRebuildCache();
-    File relinkApplicationDir = Files.createTempDir();
+    File relinkApplicationDir = createTempDir();
 
     String originalJs = compileToJs(relinkApplicationDir, "com.foo.SimpleModule", Lists
         .newArrayList(simpleModuleResource, simpleModelEntryPointResource, simpleModelResource,
@@ -2233,7 +2233,7 @@ public void checkIncrementalRecompile_primitiveClassLiteralReference(JsOutputOpt
   private void checkIncrementalRecompile_dateStampChange(JsOutputOption output)
       throws UnableToCompleteException, IOException, InterruptedException {
     MinimalRebuildCache relinkMinimalRebuildCache = new MinimalRebuildCache();
-    File relinkApplicationDir = Files.createTempDir();
+    File relinkApplicationDir = createTempDir();
 
     String originalJs = compileToJs(relinkApplicationDir, "com.foo.SimpleModule",
         Lists.newArrayList(simpleModuleResource, simpleModelEntryPointResource, simpleModelResource,
@@ -2490,7 +2490,7 @@ private void checkIncrementalRecompile_generatorInputResourceChange(JsOutputOpti
 
   private void assertCompileSucceeds(CompilerOptions options, String moduleName,
       List<MockResource> applicationResources) throws Exception {
-    File compileWorkDir = java.nio.file.Files.createTempDirectory(moduleName).toFile();
+    File compileWorkDir = Files.createTempDirectory(moduleName).toFile();
     final CompilerOptionsImpl compilerOptions = new CompilerOptionsImpl(options);
     PrintWriterTreeLogger logger = new PrintWriterTreeLogger();
     logger.setMaxDetail(TreeLogger.ERROR);
@@ -2499,7 +2499,7 @@ private void assertCompileSucceeds(CompilerOptions options, String moduleName,
         System.setProperty(UnitCacheSingleton.GWT_PERSISTENTUNITCACHE, "false");
     try {
 
-      File applicationDir = Files.createTempDir();
+      File applicationDir = createTempDir();
       Thread.sleep(1001);
       // We might be reusing the same application dir but we want to make sure that the output dir
       // is clean to avoid confusion when returning the output JS.
@@ -2552,8 +2552,8 @@ private void assertDeterministicBuild(String topLevelModule, int optimizationLev
     final CompilerOptionsImpl options = new CompilerOptionsImpl();
     options.setOptimizationLevel(optimizationLevel);
 
-    File firstCompileWorkDir = java.nio.file.Files.createTempDirectory("hellowork").toFile();
-    File secondCompileWorkDir = java.nio.file.Files.createTempDirectory("hellowork").toFile();
+    File firstCompileWorkDir = Files.createTempDirectory("hellowork").toFile();
+    File secondCompileWorkDir = Files.createTempDirectory("hellowork").toFile();
     String oldPersistentUnitCacheValue =
         System.setProperty(UnitCacheSingleton.GWT_PERSISTENTUNITCACHE, "false");
     try {
@@ -2630,7 +2630,7 @@ private void checkRecompiledModifiedApp(
 
     // Compile the app with original files, modify a file and do a per-file recompile.
     MinimalRebuildCache relinkMinimalRebuildCache = new MinimalRebuildCache();
-    File relinkApplicationDir = Files.createTempDir();
+    File relinkApplicationDir = createTempDir();
     String originalAppFromScratchJs = compileToJs(compilerOptions, relinkApplicationDir, moduleName,
         originalResources, relinkMinimalRebuildCache, emptySet, output);
     String modifiedAppRelinkedJs = compileToJs(compilerOptions, relinkApplicationDir, moduleName,
@@ -2639,7 +2639,7 @@ Lists.<MockResource> newArrayList(modifiedResource), relinkMinimalRebuildCache,
 
     // Compile the app from scratch with the modified file.
     MinimalRebuildCache fromScratchMinimalRebuildCache = new MinimalRebuildCache();
-    File fromScratchApplicationDir = Files.createTempDir();
+    File fromScratchApplicationDir = createTempDir();
     String modifiedAppFromScratchJs = compileToJs(compilerOptions, fromScratchApplicationDir,
         moduleName, modifiedResources, fromScratchMinimalRebuildCache, emptySet, output);
 
@@ -2737,7 +2737,11 @@ private String compileToJs(TreeLogger logger, CompilerOptions compilerOptions, F
     if (expectedProcessedStaleTypeNames != null) {
       assertEquals(expectedProcessedStaleTypeNames, getStaleTypeNames(minimalRebuildCache));
     }
-    return Files.toString(outputJsFile, Charsets.UTF_8);
+    return Files.readString(outputJsFile.toPath(), Charsets.UTF_8);
+  }
+
+  private static File createTempDir() throws IOException {
+    return Files.createTempDirectory("CompilerTest").toFile();
   }
 
   private Set<String> getStaleTypeNames(MinimalRebuildCache relinkMinimalRebuildCache) {
@@ -2793,6 +2797,6 @@ private void writeResourceTo(MockResource mockResource, File applicationDir) thr
     File resourceFile =
         new File(applicationDir.getAbsolutePath() + File.separator + mockResource.getPath());
     resourceFile.getParentFile().mkdirs();
-    Files.write(mockResource.getContent(), resourceFile, Charsets.UTF_8);
+    Files.write(resourceFile.toPath(), List.of(mockResource.getContent()), Charsets.UTF_8);
   }
 }
diff --git a/dev/core/test/com/google/gwt/dev/util/arg/SourceLevelTest.java b/dev/core/test/com/google/gwt/dev/util/arg/SourceLevelTest.java
index d13c62ddd73..5c95e4eddc4 100644
--- a/dev/core/test/com/google/gwt/dev/util/arg/SourceLevelTest.java
+++ b/dev/core/test/com/google/gwt/dev/util/arg/SourceLevelTest.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2024 GWT Project Authors
+ * 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
@@ -39,4 +39,4 @@ public void testVersionNumberComparisons() {
     } catch (IllegalArgumentException e) {
     }
   }
-}
\ No newline at end of file
+}