Java只允許輸入大寫字母的文本框

Java只允許輸入大寫字母的文本框：

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. * upper case 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 UpperCaseField extends JTextField {
20. /**
21. *
22. */
23. private static final long serialVersionUID = 6854878572763032459L;
25. public UpperCaseField(int cols) {
26. // 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
27. // super關鍵字顯示地調用父類的構造方法
28. super(cols);
29. }
31. protected Document createDefaultModel() {
32. return new UpperCaseDocument();
33. }
35. static class UpperCaseDocument extends PlainDocument {
37. /**
38. *
39. */
40. private static final long serialVersionUID = -4170536906715361215L;
42. public void insertString(int offs, String str, AttributeSet a)
43. throws BadLocationException {
45. if (str == null) {
46. return;
47. }
48. char[] upper = str.toCharArray();
49. for (int i = 0; i < upper.length; i++) {
50. upper[i] = Character.toUpperCase(upper[i]);
51. }
52. super.insertString(offs, new String(upper), a);
53. }
54. }
55. }