Question

我是初学者，但我一直在处理这个未知问题。请查看我编写的这个简单程序，并解释为什么它不会为我编译。问题是我从老师那里复制了这个代码，它在他的机器上工作正常。然后，当我试图在我的机器上运行该示例时，我得到13个错误！

这是第一堂课：

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

class radio extends JFrame{

 private JTextField tf;
 private Font pf;
 private Font bf;
 private Font itf;
 private Font bif;
 private JRadioButton pb;
 private JRadioButton bb;
 private JRadioButton ib;
 private JRadioButton bib;
 private ButtonGroup group;

 public radio(){
  super("raido buttonseses");
  setLayout(new FlowLayout());

  tf = new JTextField("buggedy buggedy boo", 25);
  add(tf);

  pb = new JRadioButton("plain", true);
  bb = new JRadioButton("bold", false);
  ib = new JRadioButton("italic", false);
  bib = new JRadioButton("bold and italic", false);

  add(pb);
  add(bb);
  add(ib);
  add(bib);

  group = new ButtonGroup();
  group.add(pb);
  group.add(bb);
  group.add(ib);
  group.add(bib);


  pf = new Font("Serif", Font.PLAIN, 14);
  bf = new Font("Serif", Font.BOLD, 14);
  itf = new Font("Serif", Font.ITALIC, 14);
  bif = new Font("Serif", Font.BOLD + Font.ITALIC, 14);
  tf.setFont(pf);

  //wait for event to happen pass in font obj to constructor
  pb.addItemListener(new HandlerClass(pf));
  bb.addItemListener(new HandlerClass(bf));
  ib.addItemListener(new HandlerClass(itf));
  bib.addItemListener(new HandlerClass(bif));





 }


  private class HandlerClass implements ItemListener{

  private Font font;
  // font obj gets variable font
  public HandlerClass(Font f){
   font = f;


  }

  //sets font to font obj that was passed in
  public void itemStateChanged(ItemEvent event){
   tf.setFont(font);


}


 }

    }

然后这是我一直试图运行的第二个主要类：

import javax.swing.JFrame;

public class radiobutton{
 public static void main(String[] args) {

  radio go = new radio();
  go.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
  go.setSize(300,200);
  go.setVisible(true);

 }


}

我知道有人在看这个并且认为答案是如此明显，但对于像我这样的初学者来说还不是很清楚。以下是我尝试编译时返回给我的错误：

javac radiobutton.java
./JFrame.java:1: JFrame is already defined in this compilation unit
import javax.swing.JFrame;
^
radiobutton.java:7: cannot find symbol
symbol  : method setDefaultCloseOperation(int)
location: class radio
            go.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
              ^
radiobutton.java:8: cannot find symbol
symbol  : method setSize(int,int)
location: class radio
            go.setSize(300,200);
              ^
radiobutton.java:9: cannot find symbol
symbol  : method setVisible(boolean)
location: class radio
            go.setVisible(true);
              ^
./JFrame.java:8: cannot find symbol
symbol  : variable EXIT_ON_CLOSE
location: class JFrame
            go.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                                              ^
./radio.java:19: cannot find symbol
symbol  : constructor JFrame(java.lang.String)
location: class JFrame
            super("raido buttonseses");
            ^
./radio.java:20: cannot find symbol
symbol  : method setLayout(java.awt.FlowLayout)
location: class radio
            setLayout(new FlowLayout());
            ^
./radio.java:22: cannot find symbol
symbol  : class JTExtField
location: class radio
            tf = new JTExtField("buggedy buggedy boo", 25);
                     ^
./radio.java:23: cannot find symbol
symbol  : method add(javax.swing.JTextField)
location: class radio
            add(tf);
            ^
./radio.java:30: cannot find symbol
symbol  : method add(javax.swing.JRadioButton)
location: class radio
            add(pb);
            ^
./radio.java:31: cannot find symbol
symbol  : method add(javax.swing.JRadioButton)
location: class radio
            add(bb);
            ^
./radio.java:32: cannot find symbol
symbol  : method add(javax.swing.JRadioButton)
location: class radio
            add(ib);
            ^
./radio.java:33: cannot find symbol
symbol  : method add(javax.swing.JRadioButton)
location: class radio
            add(bib);
            ^
13 errors

我的猜测是，这与导入java函数时的星号有关。我在这里走在正确的轨道上吗？感谢您查看这个愚蠢的问题，非常感谢任何帮助。

Answer 1

它对我来说很好。

错误可能是这样的：您的源目录中有另一个名为JFrame.java 的文件。删除此文件！ JFrame已经在API中定义。

错误讯息......

./JFrame.java:1: JFrame is already defined in this compilation unit
import javax.swing.JFrame;

...显示./JFrame.java与radiobutton存在于同一个包中。

（作为附注，我想提一下，根据Java编码约定，你应该总是用大写字母开始你的类名。）

Answer 2

这是一个黑暗的镜头，因为我有一段时间没有触及Java，但是你在编译radio.java，然后编译radiobutton.java吗？

Answer 3

./JFrame.java:8: cannot find symbol
symbol  : variable EXIT_ON_CLOSE
location: class JFrame
            go.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

此错误消息引用另一个源文件（JFrame.java）。就像aioobe一样，我打赌你在同一目录（包）中有一个名为JFrame.java的文件。

要测试，请尝试以下代码：

// no import statement here!

public class radiobutton{
   public static void main(String[] args) {
      radio go = new radio();
      go.setDefaultCloseOperation(javax.swing.JFrame.EXIT_ON_CLOSE);
      //                          ^ changed  ^
      go.setSize(300,200);
      go.setVisible(true);    
   }
}

Java错误对于简单的程序停止编译过程，请帮忙

3 个答案: