Java只允許輸入數字的文本框

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() 可以被自動調用，但是有參構造方法并不能被自動調用，只能依賴

// super關鍵字顯示地調用父類的構造方法

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);

}

}

}

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