如何检查Java中的文本字段是否为空并包含整数值？

Question

I have a GUI which stores the Bank Account number, during validation, I need to check if the user has entered the account number.

For string fields, isEmpty() method can be used, but what about Integer field account number.

Integer.parseInt(jTextField1.getText()).isEmpty()

would give an error, How to check for null fields when its an Integer?

Answer 1

Check is Empty before parsing it into integer like

if(!jTextField1.getText().isEmpty()){

Integer.parseInt(jTextField1.getText());

}

Answer 2

You should rather try the following code

if(!(jTextField1.getText().isEmpty()))
    {
        int accountNumber=Integer.parseInt(jTextField1.getText());
    }

Answer 3

Class Integer is just an wrapper on top of primitive int type. So it can either be null or store a valid integer value. There is no obvious "empty" definition for it.

If you just compare Integer against empty String , you''ll get false as a result. Always. See Integer.equals(Object o) implementation:

public boolean equals(Object obj) {
    if (obj instanceof Integer) {
        return value == ((Integer)obj).intValue();
    }
    return false;
}

First of all, you can get a NumberFormatException during parsing integer in the line:

Integer accountNumber = Integer.parseInt(jTextField1.getText())

And you are getting it, since For input string: "" looks like a NumberFormatExpection message.

In your example you should either check whether the "accountNumber" attribute value is a number (assume it's a string) and then parse it, or parse it as is and catch NumberFormatException that Integer.parseInt() throws on incorrect argument.

First solution:

if(!jTextField1.getText().isEmpty() && jTextField1.getText().matches("\\d+")){ //null-check and regex check to make sure the string contains only 
     Integer accountNumber = Integer.parseInt(jTextField1.getText());                 
}

Second solution:

try{
     Integer accountNumber = Integer.parseInt(jTextField1.getText());                 
}catch (NumberFormatException e) {
// handle error

}

Hope this should help you.

PS If you use Java of version 7 or higher, consider use try-with-resources to manage Connection and PreparedStatement .