Java忽略了布尔评估

Question

if (!(portField.getText().equals(""))) {                
    String p = portField.getText();
    CharSequence numbers = "0123456789";

    if (p.contains(numbers)) {

        listener = new ServerSocket(Integer.parseInt(p));

        while (true) {
            Socket socket = listener.accept();
            try {
                PrintWriter out = new PrintWriter(socket.getOutputStream(), true);
                out.println("Hi there, human.");    
            } finally {
                socket.close(); 
            }
    }} else {
        JOptionPane.showMessageDialog(null, "Only numbers are allowed.");
    }
} else {
    JOptionPane.showMessageDialog(null, "Please input a port.");
}

问题是:JOptionPane弹出"只允许数字",即使我把数字放入portField.在CharSequence和我测试过它,只允许数字来输入,因为据我所知的方式,是正确的,和Java忽略了整个街区,并跳转到该else条款.

为什么会这样？我不应该使用else和使用else if吗？

Answer 1

contains意味着包含整体0123456789.例如:"a0123456789b"

请p.matches("[0-9]*");改用.