import java.awt.*;
import java.awt.event.*;
public static void main(String[] args)
{
new AwtDemo1();
}
class AwtDemo1
{
private Frame f;
private Button b;
AwtDemo1()
{
init();
}
public void init()
{
Frame f=new Frame("my awt");
f.setSize(500,400);
f.setLocation(300,200);
f.setLayout(new FlowLayout());//设置此容器的布局管理器。来自
Container.
Button b=new Button("我是一个按钮");
f.add(b);
myEvent();//添加一个自定义的窗体事件
f.setVisible(true);
}
public void myEvent()
{
/*f.addWindowListener(new WindowAdapter()
{
public void windowClosing(WindowEvent e)
{
System.exit(0);//关闭窗口
}
});
b.addActionListener(new ActionListener(){
public void actionPerformed(ActionEvent e)
{
System.out.println("退出，按钮干的");
System.exit(0);//终止当前行正在运行的虚拟机
}
});
*/
（问题一：：：当我把上面的f和b的监听器注释掉后，他的.class文件能够运行，能够创建出f的窗口和b的按钮。但是当我不对他们的任意一个注释时编译能够通过但是在运行.class文件 是会报D:\JAVA\lianxi\day22>javac AwtDemo.java
D:\JAVA\lianxi\day22>java AwtDemo1
Exception in thread "main" java.lang.NullPointerException
at AwtDemo1.myEvent(AwtDemo.java:56)
at AwtDemo1.init(AwtDemo.java:33)
at AwtDemo1.<init>(AwtDemo.java:22)
at AwtDemo1.main(AwtDemo.java:67)
D:\JAVA\lianxi\day22>
）
（问题二：：接着上面的，就是把f和b的监听器注释掉会，他能够创建f的窗口和b的按钮，但是此时但我按下CRTll +c来结束程序时回报下面的错，D:\JAVA\lianxi\day22>javac AwtDemo.java
D:\JAVA\lianxi\day22>java AwtDemo1
#
# A fatal error has been detected by the Java Runtime Environment:
#
# EXCEPTION_ACCESS_VIOLATION (0xc0000005) at pc=0x100a7f17, pid=3928, tid=3628
#
# JRE version: 7.0_05-b05
# Java VM: Java HotSpot(TM) Client VM (23.1-b03 mixed mode, sharing windows-x86
)
# Problematic frame:
# C [GOOGLEPINYIN2.IME+0xa7f17] DllRegisterServer+0x43d47
#
# Failed to write core dump. Minidumps are not enabled by default on client vers
ions of Windows
#
# An error report file with more information is saved as:
# D:\JAVA\lianxi\day22\hs_err_pid3928.log
#
# If you would like to submit a bug report, please visit:
# http://bugreport.sun.com/bugreport/crash.jsp
# The crash happened outside the Java Virtual Machine in native code.
# See problematic frame for where to report the bug.
#
）
}
}
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