[LlamaDemo] Replace some tokens

Differential Revision: D74687286

Pull Request resolved: #10863

Author: kirklandsign

examples/demo-apps/android/LlamaDemo/app/src/main/java/com/example/executorchllamademo/MainActivity.java

@@ -90,6 +90,7 @@ public void onResult(String result) {
     if (result.equals(PromptFormat.getStopToken(mCurrentSettingsFields.getModelType()))) {
       return;
     }
+    result = PromptFormat.replaceSpecialToken(mCurrentSettingsFields.getModelType(), result);
     if (result.equals("\n\n") || result.equals("\n")) {
       if (!mResultMessage.getText().isEmpty()) {
         mResultMessage.appendText(result);

examples/demo-apps/android/LlamaDemo/app/src/main/java/com/example/executorchllamademo/PromptFormat.java

@@ -99,6 +99,22 @@ public static String getThinkingModeToken(ModelType modelType, boolean thinkingM
     }
   }
 
+  public static String replaceSpecialToken(ModelType modelType, String token) {
+    switch (modelType) {
+      case QWEN_3:
+        switch (token) {
+          case "<|im_end|>":
+            return "";
+          case "<think>":
+            return "Thinking...\n";
+          case "</think>":
+            return "\nDone thinking";
+        }
+      default:
+        return token;
+    }
+  }
+
   public static String getLlavaPresetPrompt() {
     return "A chat between a curious human and an artificial intelligence assistant. The assistant"
         + " gives helpful, detailed, and polite answers to the human's questions. USER: ";