Java只允许输入数字的文本框
package com.han;import javax.swing.JTextField;import javax.swing.text.AttributeSet;import javax.swing.text.BadLocationException;import javax.swing.text.Document;import javax.swing.text.PlainDocument;/** * Customized fields can easily be created by extending the model * and changing the default model provided. For example, * the following piece of code will create a field that holds only * digit characters. It will work even if text is pasted into from * the clipboard or it is altered via programmatic changes. * @author HAN * */public class DigitOnlyField extends JTextField { /** * */private static final long serialVersionUID = 8384787369612949227L;public DigitOnlyField(int cols) {// super() 可以被自动调用，但是有参构造方法并不能被自动调用，只能依赖// super关键字显示地调用父类的构造方法 super(cols); } protected Document createDefaultModel() { return new UpperCaseDocument(); } static class UpperCaseDocument extends PlainDocument { /** * */private static final long serialVersionUID = -4170536906715361215L;public void insertString(int offs, String str, AttributeSet a) throws BadLocationException { if (str == null) { return; } char[] upper = str.toCharArray(); String filtered = ""; for (int i = 0; i < upper.length; i++) { if (Character.isDigit(Character.codePointAt(upper, i))){ filtered += upper[i]; } } super.insertString(offs, filtered, a); } }}