refactor: add null annotations in appropriate places

core/src/main/java/com/google/adk/agents/ActiveStreamingTool.java

@@ -22,8 +22,8 @@
 
 /** Manages streaming tool related resources during invocation. */
 public class ActiveStreamingTool {
-  @Nullable private Disposable task;
-  @Nullable private LiveRequestQueue stream;
+  private @Nullable Disposable task;
+  private @Nullable LiveRequestQueue stream;
 
   public ActiveStreamingTool(Disposable task) {
     this(task, null);
@@ -41,8 +41,7 @@ public ActiveStreamingTool(Disposable task, LiveRequestQueue stream) {
   public ActiveStreamingTool() {}
 
   /** Returns the active task of this streaming tool. */
-  @Nullable
-  public Disposable task() {
+  public @Nullable Disposable task() {
     return task;
   }
 
@@ -52,8 +51,7 @@ public void task(@Nullable Disposable task) {
   }
 
   /** Returns the active stream of this streaming tool. */
-  @Nullable
-  public LiveRequestQueue stream() {
+  public @Nullable LiveRequestQueue stream() {
     return stream;
   }
 

core/src/main/java/com/google/adk/agents/LlmAgent.java

@@ -129,10 +129,10 @@ protected LlmAgent(Builder builder) {
         requireNonNullElse(builder.globalInstruction, new Instruction.Static(""));
     this.generateContentConfig = Optional.ofNullable(builder.generateContentConfig);
     this.includeContents = requireNonNullElse(builder.includeContents, IncludeContents.DEFAULT);
-    this.planning = builder.planning != null && builder.planning;
+    this.planning = requireNonNullElse(builder.planning, false);
     this.maxSteps = Optional.ofNullable(builder.maxSteps);
-    this.disallowTransferToParent = builder.disallowTransferToParent;
-    this.disallowTransferToPeers = builder.disallowTransferToPeers;
+    this.disallowTransferToParent = requireNonNullElse(builder.disallowTransferToParent, false);
+    this.disallowTransferToPeers = requireNonNullElse(builder.disallowTransferToPeers, false);
     this.beforeModelCallback = requireNonNullElse(builder.beforeModelCallback, ImmutableList.of());
     this.afterModelCallback = requireNonNullElse(builder.afterModelCallback, ImmutableList.of());
     this.onModelErrorCallback =
@@ -566,8 +566,7 @@ public Builder codeExecutor(BaseCodeExecutor codeExecutor) {
       return this;
     }
 
-    @Nullable
-    private static <B, A> ImmutableList<A> convertCallbacks(
+    private static <B, A> @Nullable ImmutableList<A> convertCallbacks(
         @Nullable List<? extends B> callbacks, Function<B, A> converter, String callbackType) {
       return Optional.ofNullable(callbacks)
           .map(

core/src/main/java/com/google/adk/apps/App.java

@@ -40,8 +40,8 @@ public class App {
   private final String name;
   private final BaseAgent rootAgent;
   private final ImmutableList<? extends Plugin> plugins;
-  @Nullable private final EventsCompactionConfig eventsCompactionConfig;
-  @Nullable private final ContextCacheConfig contextCacheConfig;
+  private final @Nullable EventsCompactionConfig eventsCompactionConfig;
+  private final @Nullable ContextCacheConfig contextCacheConfig;
 
   private App(
       String name,

core/src/main/java/com/google/adk/events/Event.java

@@ -348,7 +348,7 @@ public static class Builder {
     private String invocationId;
     private String author;
     private @Nullable Content content;
-    private EventActions actions;
+    private @Nullable EventActions actions;
     private @Nullable Set<String> longRunningToolIds;
     private @Nullable Boolean partial;
     private @Nullable Boolean turnComplete;
@@ -399,7 +399,7 @@ public Builder content(@Nullable Content value) {
 
     @CanIgnoreReturnValue
     @JsonProperty("actions")
-    public Builder actions(EventActions value) {
+    public Builder actions(@Nullable EventActions value) {
       this.actions = value;
       return this;
     }

core/src/main/java/com/google/adk/events/EventActions.java

@@ -281,7 +281,7 @@ private Builder(EventActions eventActions) {
 
     @CanIgnoreReturnValue
     @JsonProperty("skipSummarization")
-    public Builder skipSummarization(boolean skipSummarization) {
+    public Builder skipSummarization(@Nullable Boolean skipSummarization) {
       this.skipSummarization = skipSummarization;
       return this;
     }
@@ -324,7 +324,7 @@ public Builder transferToAgent(@Nullable String agentId) {
 
     @CanIgnoreReturnValue
     @JsonProperty("escalate")
-    public Builder escalate(boolean escalate) {
+    public Builder escalate(@Nullable Boolean escalate) {
       this.escalate = escalate;
       return this;
     }