Java消息框不会弹出

Question

我是Java的新手，在满足条件tempTable.size() == 1时会有以下代码，然后会弹出消息框，但它不起作用，代码停在System.out.println("Print Message No search result");行。任何人都可以帮助我为什么消息框没有弹出？

public boolean Report()throws DocumentException, IOException {

Document document = new Document(PageSize.A4, LEFT_MARGIN, RIGHT_MARGIN, TOP_MARGIN, BOTTOM_MARGIN);

    PdfPTable tempTable = constructTable();
    System.out.println("Document size is " + tempTable.size());
    if (tempTable.size() == 1) {

            try {
                System.out.println("Print Message No search result");
                JOptionPane.showMessageDialog(null, "No Search Result");
                System.out.println("Finish Print Message No search result");

            }  catch (Exception e){
                e.printStackTrace(); 
                System.out.println("throw exception on try show msgbox: "); 

            }


    }else{...}