How do validate a JtextField which will ensure that the maximum numbers typed should only be 8?

i also want to know how to add maximum number of elements foe jtextfield. but i know the code for add only integers for field


String HpNo = jTextFieldHpNo.getText();

try {
int HpNo1=Integer.parseInt(HpNo);
jOtherTextField.requestFocusInWindow();//this is what do you want if adding things are all integers. i put go to other text field
} catch (Exception e) {
JOptionPane.showMessageDialog(null, "Data Type is not correct.\n"+"Plese contact System Administrator or recheck the details", "ERROR", JOptionPane.ERROR_MESSAGE);
jTextFieldHpNo.setText("");
jTextFieldHpNo.requestFocusInWindow();
}

in this example if you add things that all are not in int type it give error message and if we select ok then clear that field and cursor is that field