编译无法通过,为什么?
我用的是j2sdk1.4.2,编译以下代码通不过(javac HelloJava1.java):
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import javax.swing.*;
import java.awt.*;
public class HelloJava1 extends JComponent
{
public static void main(String[] args)
{
JFrame f=new JFrame("HelloJava1");
f.setSize(300,300);
f.getContentPane().add(new HelloJava1());
f.setVisible(true);
}
public void paintComponent(Graphics g)
{
g.drawString("Hello Java!",125,95);
}
}
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出错提示为:
Invalid class file format: C:\j2sdk1.4.2\jre\lib\rt.jar(javax/swing/JComonent.class),wrong version:48,expected 45
Superclass javax.swing.JComponent of class HelloJava1 not found