JFrame 突然找不到符号

emptyer3011

代码是这样的:
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

/** Tiny example showing the main difference in using
*  JFrame instead of Frame: using the content pane
*  and getting the Java (Metal) look and feel.
*  1998-99 Marty Hall, http://www.apl.jhu.edu/~hall/java/
*/

public class JFrameExample {
  public static void main(String[] args) {
    WindowUtilities.setNativeLookAndFeel();
    JFrame f = new JFrame("This is a test");
    f.setSize(400, 150);
    Container content = f.getContentPane();
    content.setBackground(Color.white);
    content.setLayout(new FlowLayout());
    content.add(new JButton("Button 1"));
    content.add(new JButton("Button 2"));
    content.add(new JButton("Button 3"));
    f.addWindowListener(new ExitListener());
    f.setVisible(true);
  }
}

这段代码昨天编译还好的,今天就怎么都通不过,报错就说找不到jframe这个类,请各位大侠帮忙~!

simonsun

第一个例子：
import java.awt.*;
import java.awt.event.*;

/** A listener that you attach to the top-level Frame or JFrame of
*  your application, so quitting the frame exits the application.
*  1998-99 Marty Hall, http://www.apl.jhu.edu/~hall/java/
*/

public class ExitListener extends WindowAdapter {
  public void windowClosing(WindowEvent event) {
    System.exit(0);
  }
}
第二个：
import javax.swing.*;
import java.awt.*;

/** A few utilities that simplify using windows in Swing.
*  1998-99 Marty Hall,
*/

public class WindowUtilities { // look and feel

  /** Tell system to use native look and feel, as in previous
   *  releases. Metal (Java) LAF is the default otherwise.
   */

  public static void setNativeLookAndFeel() {
    try {
      UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
    } catch(Exception e) {
      System.out.println("Error setting native LAF: " + e);
    }
  }

  public static void setJavaLookAndFeel() {
    try {
      UIManager.setLookAndFeel(UIManager.getCrossPlatformLookAndFeelClassName());
    } catch(Exception e) {
      System.out.println("Error setting Java LAF: " + e);
    }
  }

   public static void setMotifLookAndFeel() {
    try {
      UIManager.setLookAndFeel("com.sun.java.swing.plaf.motif.MotifLookAndFeel");
    } catch(Exception e) {
      System.out.println("Error setting Motif LAF: " + e);
    }
  }

  /** A simplified way to see a JPanel or other Container.
   *  Pops up a JFrame with specified Container as the content pane.
   */

  public static JFrame openInJFrame(Container content,
                                    int width,
                                    int height,
                                    String title,
                                    Color bgColor) {
    JFrame frame = new JFrame(title);
    frame.setBackground(bgColor);
    content.setBackground(bgColor);
    frame.setSize(width, height);
    frame.setContentPane(content);
    frame.addWindowListener(new ExitListener());
    frame.setVisible(true);
    return(frame);
  }

  /** Uses Color.white as the background color. */

  public static JFrame openInJFrame(Container content,
                                    int width,
                                    int height,
                                    String title) {
    return(openInJFrame(content, width, height, title, Color.white));
  }

  /** Uses Color.white as the background color, and the
   *  name of the Container's class as the JFrame title.
   */

  public static JFrame openInJFrame(Container content,
                                    int width,
                                    int height) {
    return(openInJFrame(content, width, height,
                        content.getClass().getName(),
                        Color.white));
  }
}

第三个：
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

/** Tiny example showing the main difference in using
*  JFrame instead of Frame: using the content pane
*  and getting the Java (Metal) look and feel.
*  1998-99 Marty Hall, http://www.apl.jhu.edu/~hall/java/
*/

public class JFrameExample {
  public static void main(String[] args) {
    WindowUtilities.setNativeLookAndFeel();
    JFrame f = new JFrame("This is a test");
    f.setSize(400, 150);
    Container content = f.getContentPane();
    content.setBackground(Color.white);
    content.setLayout(new FlowLayout());
    content.add(new JButton("Button 1"));
    content.add(new JButton("Button 2"));
    content.add(new JButton("Button 3"));
    f.addWindowListener(new ExitListener());
    f.setVisible(true);
  }
}

把这仨放在一个文件夹里，javac *.java，就ok啦。。。