jtextfIELD 只能输入数字

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1 如何选择jtextfield的输入文本的样式

JTextField field = new JFormattedTextField(NumberFormat.getIntegerInstance());

field.setColumns(1);

貌似有很多方法，先记了再说...
1.限制输入数字
用法 textfield.setDocument(new IntegerDocument());   
class IntegerDocument extends PlainDocument
{   
public void insertString(int offset, String s, 
AttributeSet attributeSet) throws BadLocationException
{
      try  
{
    Integer.parseInt(s);
}
catch(Exception ex)
{
   Toolkit.getDefaultToolkit().beep();
    return;
}
super.insertString(offset, s, attributeSet);
}
}
 
2.限制输入数字和长度
public class NumberLenghtLimitedDmt extends PlainDocument {

   private int limit; 
   public NumberLenghtLimitedDmt(int limit) {
    super();
       this.limit = limit;
    } 
   public void insertString
     (int offset, String str, AttributeSet attr)
                                   throws BadLocationException {   
       if (str == null){
        return;
       }
       if ((getLength() + str.length()) <= limit) {
     
       char[] upper = str.toCharArray();
       int length=0;
       for (int i = 0; i < upper.length; i++) {     
           if (upper[i]>='0'&&upper[i]<='9'){         
              upper[length++] = upper[i];
           }
       }
         super.insertString(offset, new String(upper,0,length), attr);
      }
    }
}
用法:
JTextField   text=new JTextField();
text.setDocument(new NumberLenghtLimitedDmt(7));
那么这个文本框只能输入7位而且是只能是数字!!!
 
3.添加KeyListener
public void keyTyped(KeyEvent e)
    {
     if ((e.getKeyChar() >= e.VK_0 && e.getKeyChar() <= e.VK_9) 
      || e.getKeyChar() == e.VK_ENTER || e.getKeyChar() == e.VK_TAB
      || e.getKeyChar() == e.VK_BACK_SPACE || e.getKeyChar() == e.VK_DELETE 
      || e.getKeyChar() == e.VK_LEFT || e.getKeyChar() == e.VK_RIGHT 
      || e.getKeyChar() == e.VK_ESCAPE) 
      return;   
     e.consume();
    }
 
 
4.使用JFormattedTextField
5.貌似还能用正则表达式 - - 还不会玩，等学了补充下

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