'class' or 'interface' expected这是什么错误啊（具体在8楼） - JAVA论坛

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'class' or 'interface' expected这是什么错误啊（具体在8楼）

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

public class WeightConApplication extends JFrame
{
private JFrame mainFrame;
private JButton exitButton;
private JTextField inputField;
private JTextField messageField;
private JLabel inputLabel;

public WeightConApplication()
{
mainFrame=new JFrame("WeightConApplication");
ConButton=new JButton("Convert");
inputLabel=new JLabel("Input weight");
inputField=new JTextField(20);

Container c=mainFrame.getContentPane();
c.setLayout(new FlowLayout());

c.add(inputLabel);
c.add(inputField);
c.add(ConButton);
c.add(messageField);

mainFrame.setSize(250,125);
}

}

public static void main(String args[])
{
new WeightConApplication();
}

编译后显示：Z:\WeightConApplication.java:34: 'class' or 'interface' expected
public static void main(String args[])
^
1 error

请问这是什么意思啊？路过的大牛们请教，:-)

[此贴子已经被作者于2007-5-13 21:57:39编辑过]

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第 2 楼

得分:0

public static void main(String args[])
{
new WeightConApplication();
}
要写在public class WeightConApplication extends JFrame内部
还有ConButton没定义

第 3 楼

得分:0

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

public class WeightConApplication extends JFrame implements TextListener
{
private JFrame mainFrame;
private JButton ConButton;
private JTextField inputField;
private JTextField messageField;
private JLabel inputLabel;

public WeightConApplication()
{
mainFrame=new JFrame("WeightConApplication");
ConButton=new JButton("Convert");
inputLabel=new JLabel("Input weight");
inputField=new JTextField(20);

Container c=mainFrame.getContentPane();
c.setLayout(new FlowLayout());

c.add(inputLabel);
c.add(inputField);
c.add(ConButton);
c.add(messageField);

mainFrame.setSize(250,125);
}

public static void main(String args[])
{
new WeightConApplication();
}

}

Z:\WeightConApplication.java:6: WeightConApplication is not abstract and does not override abstract method textValueChanged(java.awt.event.TextEvent) in java.awt.event.TextListener
public class WeightConApplication extends JFrame implements TextListener
^
1 error

我又不明白了，java真难学啊- -||

第 4 楼

得分:0

实现TextListener应该还有一个

对应的方法吧

第 5 楼

得分:0

回复：（Sieben7）\'class\' or \'interface\' expected这...

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

public class WeightConApplication extends JFrame //implements TextListener
{
private JFrame mainFrame;
private JButton ConButton;
private JTextField inputField;
private JTextField messageField;
private JLabel inputLabel;

public WeightConApplication()
{
mainFrame=new JFrame("WeightConApplication");
ConButton=new JButton("Convert");
inputLabel=new JLabel("Input weight");
inputField=new JTextField(20);

Container c=mainFrame.getContentPane();
c.setLayout(new FlowLayout());

c.add(inputLabel);
c.add(inputField);
c.add(ConButton);
c.add(messageField);

mainFrame.setSize(250,125);
}

public static void main(String args[])
{
new WeightConApplication();
}

}

这样可以编译，不过在3楼的问题我还是不知道是什么意思。

第 6 楼

得分:0

回复：（Sieben7）\'class\' or \'interface\' expected这...

其实这道问题是这样的：
编写java独立应用程序，接收人在地球上体重，输出他在月球上的体重。

（1）月球上人的体重是在地球上体重的1/6。

（2）定义可实例化类，以实现人在地球上的体重与在月球上体重的转换。

（3）使用图形用户界面组件标签、文本框、按钮。

（4）处理输入错误的情况。

我的代码如下：

import java.awt.event.*;
import java.awt.*;

public class WeightConApplication extends Frame implements ActionListener,WindowListener{
public Frame mainFrame;
public Button ConButton;
public TextField inputField;
public TextField messageField;
public Label inputLabel;

WeightConApplication()
{
setLayout(new FlowLayout());
inputField=new TextField(20);
inputLabel=new Label("Input weight");
ConButton=new Button("Convert");

add(ConButton);
add(inputField);
add(messageField);
add(inputLabel);

ConButton.addActionListener(this);
setBounds(100,100,150,150);
setVisible(true);

//mainFrame.setSize(250,125);
addWindowListener(new WindowAdapter() {
public void windowClosing(WindowEvent e) {
dispose();
System.exit(0);
}
});
validate();

}

public static void main(String args[])
{
System.out.println("Starting WeightConApplication...");
WeightConApplication mainFrame = new WeightConApplication();
mainFrame.setSize(400, 400);
mainFrame.setTitle("WeightConApplication");
mainFrame.setVisible(true);
}

public void actionPerformed(ActionEvent exception)
{

try{
if(exception.getSource()==ConButton){
messageField.setText(Double.parseDouble(inputField.getText())/6);
}
}
catch(NumberFormatException e)
{
messageField.setText("非法字符");}
}
}

编译后有两个错误：
Z:\WeightConApplication.java:4: WeightConApplication is not abstract and does not override abstract method windowDeactivated(java.awt.event.WindowEvent) in java.awt.event.WindowListener
public class WeightConApplication extends Frame implements ActionListener,WindowListener{
^
Z:\WeightConApplication.java:55: cannot find symbol
symbol : method setText(double)
location: class java.awt.TextField
messageField.setText(Double.parseDouble(inputField.getText())/6);
^
2 errors

热心的斑斑或者路过的大牛们能够指点指点，我实在是没办法。java书上的例子很容易看懂，一到自己动手了就开始不行了。

第 7 楼

得分:0

1.WindowListener接口的抽象方法需要实现
2.messageField.setText(String );参数是string型!

我的网站 http://www.

第 8 楼

得分:0

回复：（Sieben7）\'class\' or \'interface\' expected这...

import java.awt.event.*;
import java.awt.*;

public class WeightConApplication extends Frame implements ActionListener{
public static void main(String args[])
{
System.out.println("Starting WeightConApplication...");
new WeightConApplication();
WeightConApplication mainFrame = new WeightConApplication();
mainFrame.setSize(400, 400);
mainFrame.setTitle("WeightConApplication");
mainFrame.setVisible(true);
}
public Button ConButton;
public TextArea inputField;
public TextArea messageField;
public Label inputLabel;

WeightConApplication()
{
setLayout(new FlowLayout());
inputField=new TextArea(6,15);
inputLabel=new Label("Input weight");
ConButton=new Button("Convert");

inputField=new TextArea(6,15);
messageField=new TextArea(6,15);

add(ConButton);
add(inputField);
add(messageField);
add(inputLabel);

setBounds(100,100,300,300);
setVisible(true);
ConButton.addActionListener(this);
setBounds(100,100,150,150);
validate();

}
public void actionPerformed(ActionEvent e)
{
messageField.append(Double.valueOf(inputField.getText())/6); //这里出了问题？
}

}

7楼的问题我考虑了，可是还是没有搞定这题- -||||

Z:\WeightConApplication.java:44: append(java.lang.String) in java.awt.TextArea cannot be applied to (double)
messageField.append(Double.valueOf(inputField.getText())/6);
^
1 error

说是不能转化成double型？

[此贴子已经被作者于2007-5-13 21:56:36编辑过]

第 9 楼

得分:0

public void actionPerformed(ActionEvent e)
{
Double m=Double.valueOf(inputField.getText())/6;
String n=m.toString();
messageField.append(n); //这里出了问题？
}
JField.append(String a),将其计算出的Double数据转换成字符串?
建议:异常要处理,加入关闭JFrame的代码setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

在不断的拼搏与进取中,定能创造一片天地!

第 10 楼

得分:0

和JField有什么关系，呵呵我没用swing组件啊。嗯，知道问题出现哪里了，谢谢大家！谢谢斑斑！

[此贴子已经被作者于2007-5-14 19:00:31编辑过]