将数值变量从HTML传递到Java

Question

This is my java class and I got NumberFormatException . Can anyone help me? I have tried many times but it keeps having that error.

public class HelloFromHTML extends JApplet
{

    String name;
    String age, dimensions1 ,dimensions2;
    int num;
    Font f;

    public void init()
    {   
        f = new Font("TimesRoman", Font.BOLD,30);

        String a = this.getParameter("ageHTML");
        num = Integer.parseInt(a);      

        name = "Hello " + getParameter("nameHTML") + " " + num + " years'"; 
        dimensions1 = "JApplet size is " + getParameter("width") + ", " +  getParameter("height");  
        dimensions2 = "size is " + String.valueOf(getWidth()) + ", " +  String.valueOf(getHeight());
    }

    public void paint(Graphics g)
    {
        super.paint(g);

        g.setFont(f);
        g.setColor(Color.black);

        //////////////////////////////////
        //   Display String
        g.drawString(name,5,50);
        g.drawString(dimensions1,5,100);
        g.drawString(dimensions2,5,200);
    }
}

Answer 1

Since the line num = Integer.parseInt(a); causes that Exception to be thrown, i advice you to surround it with a try-catch block. And also, debug your code to see why a is not a number. It is a good practice to catch any Exception that may be thrown.

try{
    num = Integer.parseInt(a);
}
catch(NumberFormatException e){
   //TODO: what happens when "a" is not a number
}