When i click on Build>Clean Project it gives me an error Failed to complete Gradle execution.

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_fun_facts);

    //Declare our View Variables and assign the the Views from the layout file
    final TextView factLabel = (TextView) findViewById(R.id.factTextView);
    Button showFactButton = (Button) findViewById(R.id.showFactButton);
    final RelativeLayout relativeLayout = (RelativeLayout) findViewById(R.id.relativeLayout);

    View.OnClickListener listener = new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            String fact = mFactBook.getFact();
            //update the label with our dynamic fact
            factLabel.setText("fact");
            relativeLayout.setBackgroundColor(Color.RED);
        }
    };
    showFactButton.setOnClickListener(listener);


}

<TextView
    android:text="Did you know?"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:textSize="24sp"
    android:textColor="#80ffffff" />

<TextView
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="The ants stretch when they wake up in the morning."
    android:id="@+id/factTextView"
    android:layout_centerVertical="true"
    android:layout_alignParentLeft="true"
    android:layout_alignParentStart="true"
    android:textSize="24sp"
    android:textColor="@android:color/white" />

<Button
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:text="Show Another Fun Fact"
    android:id="@+id/showFactButton"
    android:layout_alignParentBottom="true"
    android:layout_centerHorizontal="true"
    android:background="@android:color/white" />