问题在哪呢？

源码如下：
import javax.Swing.*;
import java.awt.*;
import java.awt.event.*;

public class FrameTester{

public static void main(String args[]){
JFrame f=new JFrame("JFrame Example");
Container c=f.getContentPane();
c.setLayout( new FlowLayout());
c.add(new JLabel("这是一个JFrame的一般示例！"));
f.setSize(300,70);
f.show();

f.addWindowLister(new WindowAdapter(){

public void windowClosing(WindowEvent e){
System.exit(0);
}

});

}
}

编译结果如下：
FrameTester.java:1: package javax.Swing does not exist
import javax.Swing.*;
^
FrameTester.java:8: cannot resolve symbol
symbol : class JFrame
location: class FrameTester
JFrame f=new JFrame("JFrame Example");
^
FrameTester.java:8: cannot resolve symbol
symbol : class JFrame
location: class FrameTester
JFrame f=new JFrame("JFrame Example");
^
FrameTester.java:11: cannot resolve symbol
symbol : class JLabel
location: class FrameTester
c.add(new JLabel("这是一个JFrame的一般示例！"));
^
4 errors


最后发现：
import javax.Swing.*;

swing 要小写

import javax.swing.*;

结论：初学者要好好学习JAVA的编码规范