Java当字段为空时抛出异常错误

Question

当文本字段为空时，我遇到此异常，即使我检查其是否为空，它也会抛出异常错误。你能看一下这个方法并告诉我哪里出了问题吗？

private void addStaff()
{
    ControlPanelCtr logCtr = new ControlPanelCtr();
    String username = userField.getText();
    String password = passField.getText();
    int secLevel = Integer.parseInt(secLvField.getText());
    if(userField.getText().equals("") || passField.getText().equals("") || secLvField.getText().equals(""))
    {
        notificationField.setText("All fields must be fullfiled.");
    }
    else
    {
        try{
            Login usrObj = new Login();
            if(usrObj.getUsername().equals(username))
            {

            }
            else
            {
                Login logObj = new Login();
                admLogIdField.setText(String.valueOf(logObj.getId()));
                logCtr.addPeople(username, password, secLevel);
            }
        }
        catch(Exception e)
        {
            notificationField.setText("Username already exists in the database.");
            Toolkit.getDefaultToolkit().beep();
        }
    }
} 

谢谢。

Answer 1

您确实检查了 secLvField 是否为非空，但为时已晚:您在尝试解析该字段以获取整数后检查该字段，这当然会抛出错误，因此支票永远不会到达。

这一行

int secLevel = Integer.parseInt(secLvField.getText());

当secLevel为空或不代表有效整数时将抛出异常。您可以将解析包装在 try/catch block 中以查看是否成功:

int secLevel;
try {
    secLevel = Integer.parseInt(secLvField.getText());
} catch (NumberFormatException nfe) {
    secLevel = -1; // If -1 is valid, pick some invalid value
}
if (secLevel == -1 || userField.getText().equals("") || passField.getText().equals("")) {
    notificationField.setText("All fields must be fullfiled.");
}
...