GWT client "throws Exception" cause compling problem

I try to use get result from a api called j-calais, and then out put the result on a web page, i write all the code in client, but it cant compile right, dont know why??? please help. the source code like below:

there is no obvious error arise, but it cant be compile successfully..... thanks a lot:

public void onModuleLoad() { // Create table for stock data. stocksFlexTable.setText(0, 0, "Type"); stocksFlexTable.setText(0, 1, "Name");

// Assemble Add Stock panel.
addPanel.add(newSymbolTextBox);
addPanel.add(addStockButton);

// Assemble Main panel.
mainPanel.add(stocksFlexTable);
mainPanel.add(addPanel);
mainPanel.add(lastUpdatedLabel);

// Associate the Main panel with the HTML host page.
RootPanel.get("stockList").add(mainPanel);

// Move cursor focus to the input box.
newSymbolTextBox.setFocus(true);

// Listen for mouse events on the Add button. addStockButton.addClickHandler(new ClickHandler() { public void onClick(ClickEvent event) {

                        try {
                            addStock();
                        } catch (Exception e) {
                            e.printStackTrace();
                        }

  }
});
// Listen for keyboard events in the input box.
newSymbolTextBox.addKeyPressHandler(new KeyPressHandler() {
  public void onKeyPress(KeyPressEvent event) {
    if (event.getCharCode() == KeyCodes.KEY_ENTER) {  
            try {
                addStock();
            } catch (Exception e) {
                e.printStackTrace();
            }
  }
  }
});

}

private void addStock() throws Exception {
  final String url_s = newSymbolTextBox.getText().toUpperCase().trim();
  newSymbolTextBox.setFocus(true);
  newSymbolTextBox.setText("");
  in开发者_如何学编程t row = stocksFlexTable.getRowCount();


  CalaisClient client = new CalaisRestClient("ysw5rx69jkvdnzqf6sgjduqj");
    System.out.print("read success...\n");
     URL url = new URL(url_s);    
     CalaisResponse response = client.analyze(url);         
        for (CalaisObject entity : response.getEntities()) {
            System.out.println(entity.getField("_type") + ":" 
                               + entity.getField("name"));
            stocks.add(entity.getField("_type"));
            stocksFlexTable.setText(row, 0, entity.getField("_type"));
            stocksFlexTable.setText(row, 1, entity.getField("name"));
          }

        for (CalaisObject topic : response.getTopics()) {
            System.out.println(topic.getField("categoryName"));
          }

}

}

GWT only handles unchecked exceptions so you can throw Runtime Exceptions

or write your own Exception that extends from Runtime Exception then it will not cause any compile time problem

void f() throws NullPointerException // will not cause any problem because it is Runtime exception so unchecked

void f() throws IllegalAccessException // it is checked exception so there will be problem at compile time