operationbutton.java

书上的例子

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

public class OperationButton extends JButton {
    String operateSign;

    public OperationButton(String s) {
        super(s);
        operateSign = s;
        setForeground(Color.red);
    }

    public String getOperateSign() {
        return operateSign;
    }
}