Java只允許輸入數字的文本框

Java只允許輸入數字的文本框：

1. package com.han;
3. import javax.swing.JTextField;
4. import javax.swing.text.AttributeSet;
5. import javax.swing.text.BadLocationException;
6. import javax.swing.text.Document;
7. import javax.swing.text.PlainDocument;
9. /**
10. * Customized fields can easily be created by extending the model
11. * and changing the default model provided. For example,
12. * the following piece of code will create a field that holds only
13. * digit characters. It will work even if text is pasted into from
14. * the clipboard or it is altered via programmatic changes.
15. * @author HAN
16. *
17. */
18. public class DigitOnlyField extends JTextField {
22. /**
23. *
24. */
25. private static final long serialVersionUID = 8384787369612949227L;
27. public DigitOnlyField(int cols) {
28. // super() 可以被自動調用，但是有參構造方法並不能被自動調用，只能依賴
29. // super關鍵字顯示地調用父類的構造方法
30. super(cols);
31. }
33. protected Document createDefaultModel() {
34. return new UpperCaseDocument();
35. }
37. static class UpperCaseDocument extends PlainDocument {
39. /**
40. *
41. */
42. private static final long serialVersionUID = -4170536906715361215L;
44. public void insertString(int offs, String str, AttributeSet a)
45. throws BadLocationException {
47. if (str == null) {
48. return;
49. }
50. char[] upper = str.toCharArray();
51. String filtered = "";
52. for (int i = 0; i < upper.length; i++) {
53. if (Character.isDigit(Character.codePointAt(upper, i))){
54. filtered += upper[i];
55. }
56. }
57. super.insertString(offs, filtered, a);
58. }
59. }
60. }