簡單程序停止編譯過程中的Java錯誤，請幫忙

Question

我是初學者，但我一直在處理這個未知問題。請查看我已編碼的這個簡單程序，並解釋它爲什麼不能編譯我。問題是我已經從老師那裏複製了這段代碼，並且在他的機器上工作正常。然後，當我試圖在我的機器上運行這個例子時，我得到了13個錯誤！

這是第一類：

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); 


} 


} 

    } 

當年這裏是我一直在試圖運行第二個主類：

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); 

} 


} 

我知道有人在看着這個和思考的答案是如此明顯，但對於像我這樣的初學者來說，這不是很清楚。下面是當我嘗試編譯，我又回到了我的錯誤：

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 

我的猜測是，這事做在的Java函數進口的星號。我在正確的軌道上嗎？感謝您看看這個愚蠢的問題，並非常感謝任何幫助。

Answer 1

這是在黑暗中拍攝的，因爲我還沒有碰過Java一段時間，但是你在編譯radio.java，然後編譯radiobutton.java？

Answer 2

它編譯得很好。

錯誤可能是這樣的：你的源代碼目錄中有另一個文件叫JFrame.java。刪除此文件！ JFrame已經在API中定義。

錯誤消息...

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

...表明./JFrame.java存在於同一個包radiobutton。

（作爲一個方面說明我想提一提的是，根據Java編碼慣例，你應該總是以大寫字母開頭的類名。）

Answer 3

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

此錯誤消息是指另一個源文件（ JFrame.java）。和aioobe一樣，我打賭你在同一個目錄（包）中有一個名爲JFrame.java的文件。

爲了測試，試試這個代碼：

// 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);  
    } 
}