限制JTextField输入控件的最大允许输入字符串的长度，jtextfield控件,Javaimport c

限制JTextField输入控件的最大允许输入字符串的长度，jtextfield控件,Javaimport c

Java

import com.sun.java.swing.text.*;public class JTextFieldLimit extends PlainDocument {  private int limit;  // optional uppercase conversion  private boolean toUppercase = false;  JTextFieldLimit(int limit) {   super();   this.limit = limit;   }  JTextFieldLimit(int limit, boolean upper) {   super();   this.limit = limit;   toUppercase = upper;   }  public void insertString    (int offset, String  str, AttributeSet attr)      throws BadLocationException {   if (str == null) return;   if ((getLength() + str.length()) <= limit) {     if (toUppercase) str = str.toUpperCase();     super.insertString(offset, str, attr);     }   }}

```{.java}import java.awt.;import javax.swing.;

public class DemoJTextFieldWithLimit extends JApplet{ JTextField textfield1; JLabel label1;

public void init() { getContentPane().setLayout(new FlowLayout()); // label1 = new JLabel("max 10 chars"); textfield1 = new JTextField(15); getContentPane().add(label1); getContentPane().add(textfield1); textfield1.setDocument (new JTextFieldLimit(10)); }}```