refactor: Using computeIfAbsent to not create unnecessary instances

core/src/main/java/com/google/adk/artifacts/InMemoryArtifactService.java

@@ -48,11 +48,8 @@ public InMemoryArtifactService() {
   public Single<Integer> saveArtifact(
       String appName, String userId, String sessionId, String filename, Part artifact) {
     List<Part> versions =
-        artifacts
-            .computeIfAbsent(appName, k -> new HashMap<>())
-            .computeIfAbsent(userId, k -> new HashMap<>())
-            .computeIfAbsent(sessionId, k -> new HashMap<>())
-            .computeIfAbsent(filename, k -> new ArrayList<>());
+        getArtifactsMap(appName, userId, sessionId)
+            .computeIfAbsent(filename, unused -> new ArrayList<>());
     versions.add(artifact);
     return Single.just(versions.size() - 1);
   }
@@ -66,11 +63,8 @@ public Single<Integer> saveArtifact(
   public Maybe<Part> loadArtifact(
       String appName, String userId, String sessionId, String filename, Optional<Integer> version) {
     List<Part> versions =
-        artifacts
-            .getOrDefault(appName, new HashMap<>())
-            .getOrDefault(userId, new HashMap<>())
-            .getOrDefault(sessionId, new HashMap<>())
-            .getOrDefault(filename, new ArrayList<>());
+        getArtifactsMap(appName, userId, sessionId)
+            .computeIfAbsent(filename, unused -> new ArrayList<>());
 
     if (versions.isEmpty()) {
       return Maybe.empty();
@@ -97,13 +91,7 @@ public Single<ListArtifactsResponse> listArtifactKeys(
       String appName, String userId, String sessionId) {
     return Single.just(
         ListArtifactsResponse.builder()
-            .filenames(
-                ImmutableList.copyOf(
-                    artifacts
-                        .getOrDefault(appName, new HashMap<>())
-                        .getOrDefault(userId, new HashMap<>())
-                        .getOrDefault(sessionId, new HashMap<>())
-                        .keySet()))
+            .filenames(ImmutableList.copyOf(getArtifactsMap(appName, userId, sessionId).keySet()))
             .build());
   }
 
@@ -115,11 +103,7 @@ public Single<ListArtifactsResponse> listArtifactKeys(
   @Override
   public Completable deleteArtifact(
       String appName, String userId, String sessionId, String filename) {
-    artifacts
-        .getOrDefault(appName, new HashMap<>())
-        .getOrDefault(userId, new HashMap<>())
-        .getOrDefault(sessionId, new HashMap<>())
-        .remove(filename);
+    getArtifactsMap(appName, userId, sessionId).remove(filename);
     return Completable.complete();
   }
 
@@ -132,15 +116,19 @@ public Completable deleteArtifact(
   public Single<ImmutableList<Integer>> listVersions(
       String appName, String userId, String sessionId, String filename) {
     int size =
-        artifacts
-            .getOrDefault(appName, new HashMap<>())
-            .getOrDefault(userId, new HashMap<>())
-            .getOrDefault(sessionId, new HashMap<>())
-            .getOrDefault(filename, new ArrayList<>())
+        getArtifactsMap(appName, userId, sessionId)
+            .computeIfAbsent(filename, unused -> new ArrayList<>())
             .size();
     if (size == 0) {
       return Single.just(ImmutableList.of());
     }
     return Single.just(IntStream.range(0, size).boxed().collect(toImmutableList()));
   }
+
+  private Map<String, List<Part>> getArtifactsMap(String appName, String userId, String sessionId) {
+    return artifacts
+        .computeIfAbsent(appName, unused -> new HashMap<>())
+        .computeIfAbsent(userId, unused -> new HashMap<>())
+        .computeIfAbsent(sessionId, unused -> new HashMap<>());
+  }
 }

core/src/main/java/com/google/adk/codeexecutors/CodeExecutorContext.java

@@ -89,7 +89,8 @@ public void setExecutionId(String sessionId) {
    * @return A list of processed file names in the code executor context.
    */
   public List<String> getProcessedFileNames() {
-    return (List<String>) this.context.getOrDefault(PROCESSED_FILE_NAMES_KEY, new ArrayList<>());
+    return (List<String>)
+        this.context.computeIfAbsent(PROCESSED_FILE_NAMES_KEY, unused -> new ArrayList<>());
   }
 
   /**
@@ -100,7 +101,7 @@ public List<String> getProcessedFileNames() {
   public void addProcessedFileNames(List<String> fileNames) {
     List<String> processedFileNames =
         (List<String>)
-            this.context.computeIfAbsent(PROCESSED_FILE_NAMES_KEY, k -> new ArrayList<>());
+            this.context.computeIfAbsent(PROCESSED_FILE_NAMES_KEY, unused -> new ArrayList<>());
     processedFileNames.addAll(fileNames);
   }
 
@@ -126,7 +127,7 @@ public List<File> getInputFiles() {
   public void addInputFiles(List<File> inputFiles) {
     List<Map<String, Object>> fileMaps =
         (List<Map<String, Object>>)
-            this.sessionState.computeIfAbsent(INPUT_FILE_KEY, k -> new ArrayList<>());
+            this.sessionState.computeIfAbsent(INPUT_FILE_KEY, unused -> new ArrayList<>());
     for (File inputFile : inputFiles) {
       fileMaps.add(
           objectMapper.convertValue(inputFile, new TypeReference<Map<String, Object>>() {}));
@@ -166,7 +167,7 @@ public int getErrorCount(String invocationId) {
   public void incrementErrorCount(String invocationId) {
     Map<String, Integer> errorCounts =
         (Map<String, Integer>)
-            this.sessionState.computeIfAbsent(ERROR_COUNT_KEY, k -> new HashMap<>());
+            this.sessionState.computeIfAbsent(ERROR_COUNT_KEY, unused -> new HashMap<>());
     errorCounts.put(invocationId, getErrorCount(invocationId) + 1);
   }
 
@@ -176,9 +177,6 @@ public void incrementErrorCount(String invocationId) {
    * @param invocationId The invocation ID to reset the error count for.
    */
   public void resetErrorCount(String invocationId) {
-    if (!this.sessionState.containsKey(ERROR_COUNT_KEY)) {
-      return;
-    }
     Map<String, Integer> errorCounts =
         (Map<String, Integer>) this.sessionState.get(ERROR_COUNT_KEY);
     if (errorCounts != null) {
@@ -198,9 +196,10 @@ public void updateCodeExecutionResult(
       String invocationId, String code, String resultStdout, String resultStderr) {
     Map<String, List<Map<String, Object>>> codeExecutionResults =
         (Map<String, List<Map<String, Object>>>)
-            this.sessionState.computeIfAbsent(CODE_EXECUTION_RESULTS_KEY, k -> new HashMap<>());
+            this.sessionState.computeIfAbsent(
+                CODE_EXECUTION_RESULTS_KEY, unused -> new HashMap<>());
     List<Map<String, Object>> resultsForInvocation =
-        codeExecutionResults.computeIfAbsent(invocationId, k -> new ArrayList<>());
+        codeExecutionResults.computeIfAbsent(invocationId, unused -> new ArrayList<>());
     Map<String, Object> newResult = new HashMap<>();
     newResult.put("code", code);
     newResult.put("result_stdout", resultStdout);
@@ -210,6 +209,7 @@ public void updateCodeExecutionResult(
   }
 
   private Map<String, Object> getCodeExecutorContext(Map<String, Object> sessionState) {
-    return (Map<String, Object>) sessionState.computeIfAbsent(CONTEXT_KEY, k -> new HashMap<>());
+    return (Map<String, Object>)
+        sessionState.computeIfAbsent(CONTEXT_KEY, unused -> new HashMap<>());
   }
 }

core/src/main/java/com/google/adk/flows/llmflows/Functions.java

@@ -52,7 +52,6 @@
 import io.reactivex.rxjava3.disposables.Disposable;
 import io.reactivex.rxjava3.functions.Function;
 import java.util.ArrayList;
-import java.util.Collections;
 import java.util.HashMap;
 import java.util.HashSet;
 import java.util.List;
@@ -332,7 +331,7 @@ private static Maybe<Map<String, Object>> processFunctionLive(
           ActiveStreamingTool activeTool =
               invocationContext
                   .activeStreamingTools()
-                  .getOrDefault(tool.name(), new ActiveStreamingTool(subscription));
+                  .computeIfAbsent(tool.name(), unused -> new ActiveStreamingTool(subscription));
           activeTool.task(subscription);
           invocationContext.activeStreamingTools().put(tool.name(), activeTool);
 
@@ -607,12 +606,7 @@ private static Event buildResponseEvent(
               .invocationId(invocationContext.invocationId())
               .author(invocationContext.agent().name())
               .branch(invocationContext.branch())
-              .content(
-                  Optional.of(
-                      Content.builder()
-                          .role("user")
-                          .parts(Collections.singletonList(partFunctionResponse))
-                          .build()))
+              .content(Content.builder().role("user").parts(partFunctionResponse).build())
               .actions(toolContext.eventActions())
               .build();
       Tracing.traceToolResponse(invocationContext, event.id(), event);

tutorials/live-audio-single-agent/src/main/java/com/google/adk/tutorials/LiveAudioSingleAgent.java

@@ -30,13 +30,12 @@ public class LiveAudioSingleAgent {
           .model("gemini-2.0-flash-live-001")
           .description("A helpful weather assistant that provides weather information.")
           .instruction(
-              "You are a friendly weather assistant. When users ask about weather, "
-                  + "you MUST call the getWeather tool with the location name. "
-                  + "Extract the location from the user's question. "
-                  + "ALWAYS use the getWeather tool to get accurate information - never make up weather data. "
-                  + "After getting the tool result, provide a friendly and descriptive response. "
-                  + "For general conversation or greetings, respond naturally and helpfully. "
-                  + "Do NOT use code execution for anything.")
+              "You are a friendly weather assistant. When users ask about weather, you MUST call"
+                  + " the getWeather tool with the location name. Extract the location from the"
+                  + " user's question. ALWAYS use the getWeather tool to get accurate information -"
+                  + " never make up weather data. After getting the tool result, provide a friendly"
+                  + " and descriptive response. For general conversation or greetings, respond"
+                  + " naturally and helpfully. Do NOT use code execution for anything.")
           .tools(FunctionTool.create(LiveAudioSingleAgent.class, "getWeather"))
           .build();
 
@@ -89,16 +88,17 @@ public static Map<String, String> getWeather(
 
     String normalizedLocation = location.toLowerCase().trim();
 
-    return weatherData.getOrDefault(
+    return weatherData.computeIfAbsent(
         normalizedLocation,
-        Map.of(
-            "status",
-            "error",
-            "report",
-            String.format(
-                "Weather information for '%s' is not available. Try New York, London, Tokyo, or"
-                    + " Sydney.",
-                location)));
+        unused ->
+            Map.of(
+                "status",
+                "error",
+                "report",
+                String.format(
+                    "Weather information for '%s' is not available. Try New York, London, Tokyo,"
+                        + " or Sydney.",
+                    location)));
   }
 
   public static void main(String[] args) {