什么原因导致“找不到符号"?以及如何解决它? [英] What causes "Can't find Symbol" and how to fix it?

问题描述

我一直在努力解决这个问题，我在不同的程序中运行过它，所以它肯定在代码中.可能也很容易.错误说

I've been trying to figure this out, I've run it in different programs so it's definitely in the code. Probably something easy too. The error says

Password2.java:90: 错误:找不到符号if(pw.equals(密码))^符号:可变密码位置:类 Password2.EnterButtonHandler1 个错误

Password2.java:90: error: cannot find symbol if(pw.equals(password)) ^ symbol: variable password location: class Password2.EnterButtonHandler 1 error

代码如下:

// Password1.java

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

public class Password2 extends JFrame // inherits from the JFrame class 
{
    // static final variables to hold frame dimensions (in pixels) 
    private static final int WIDTH = 400;
    private static final int HEIGHT = 120;

    //declare labels, fields, buttons, etc.
    private JLabel enterLabel, validLabel, resultLabel;
    private JTextField pwTextField;
    private JButton enterB, clearB;

    private EnterButtonHandler ebHandler;
    private ClearButtonHandler cbHandler;

    public Password2() // constructor defines frame 
    { 
            setTitle( "Password Checker" ); // set the title of the frame
        setSize( WIDTH, HEIGHT ); // set the frame size

        // prepare the container 
        Container pane = getContentPane();
        GridLayout aGrid = new GridLayout( 3, 2, 5, 5 ); // create a 3 row 2 column layout
        pane.setLayout( aGrid ); // set the layout for the frame

        String password = "hello";

        //instantiate JLabels
        enterLabel = new JLabel("Enter Password: ");
        validLabel = new JLabel("Validation: ");
        resultLabel = new JLabel("");

        //instantiate text fields
        pwTextField = new JPasswordField( 30 );

        //instantiate buttons
        enterB = new JButton("Enter");
        clearB = new JButton("Clear");

        //initialize button handler
        ebHandler = new EnterButtonHandler();
        enterB.addActionListener(ebHandler);

        //initialize button handler
        cbHandler = new ClearButtonHandler();
        clearB.addActionListener(cbHandler);


        pane.add(enterLabel);
        pane.add(pwTextField);
        pane.add(validLabel);
        pane.add(resultLabel);
        pane.add(enterB);
        pane.add(clearB);

        //calls center frame method
        centerFrame( WIDTH, HEIGHT );

    }// end constructor

    //methood to center GUI on screen
    public void centerFrame( int frameWidth, int frameHeight)
    {
        //create toolkit object
        Toolkit aToolkit = Toolkit.getDefaultToolkit();

        //create a dimension object with user screen information
        Dimension screen = aToolkit.getScreenSize();

        //assign x, y position of upper left corner of frame
        int xUpperLeft = ( screen.width - frameWidth ) / 2;
        int yUpperLeft = ( screen.height - frameHeight ) / 2;

        //method to position frame on user's screen
        setBounds( xUpperLeft, yUpperLeft, frameWidth, frameHeight );
    }

    private class EnterButtonHandler implements ActionListener
    {
        public void actionPerformed(ActionEvent e)
        {
            String pw = pwTextField.getText();

            if(pw.equals(password))
            {
                resultLabel.setText("Password Accepted");
                pwTextField.setText("");
            }
            else
            {
                resultLabel.setText("Password Rejected");
                pwTextField.setText("");
            }
        }
    }
    private class ClearButtonHandler implements ActionListener
    {
        public void actionPerformed(ActionEvent e)
        {
            resultLabel.setText("");
            pwTextField.setText("");
        }

    }
    public static void main(String [] args) 
    {
        JFrame aPassword2 = new Password2(); // create the JFrame object
        aPassword2.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        aPassword2.setVisible(true);
    }
    } // end of class

推荐答案

阅读错误信息，喜欢错误信息.

Read the error message, love the error message.

这需要一些练习，但过一会儿就很容易看清楚了:只需将下面的粗体文本作为句子阅读:)

It takes some practice, but after awhile it's easy to see it more clearly: just read across the bold text below as a sentence :)

错误:找不到符号 [...]

符号:变量密码

位置:[in] class Password2.EnterButtonHandler

location: [in] class Password2.EnterButtonHandler

在该范围/上下文中没有名为 password 的内容 (EnterButtonHandler).

There is nothing named password in that scope/context (EnterButtonHandler).

快乐编码.

提示:在不同范围/上下文中有一个同名的local变量......也许它不应该是localem> 变量?有关更多信息，请参阅 Java 教程:变量 :)

Hint: there is a local variable with the same name in a different scope/context... perhaps it shouldn't be a local variable? See The Java Tutorial: Variables for more :)

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