import java.awt.*;
import java.util.Date;public class showDate extends java.applet.Applet{
String rem="abcd";
//String title;
Date timeNow=new Date();
Font msgFont=new Font("TimesRoman",Font.ITALIC,30);
String title=getParameter(rem);
public void paint(Graphics g)
{ g.setFont(msgFont);
g.setColor(Color.blue);
//g.drawString(timeNow.toString(),5,50);
g.drawString(title+timeNow.toString(),5,50);
}
public void init()
{title=getParameter
("rem");
if (title==null)
title="";
}
}
比如:
<html>
<body>
Here comes my first applet:
<br>
<applet code="showDate.class" width="650" height="500"></applet>
</body>
</html>然后打开这个网页就行
java.lang.NullPointerException
at java.applet.Applet.getParameter(Applet.java:158)
at showDate.<init>(showDate.java:9)
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstruct
orAccessorImpl.java:39)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingC
onstructorAccessorImpl.java:27)
at java.lang.reflect.Constructor.newInstance(Constructor.java:415)
at java.lang.Class.newInstance0(Class.java:322)
at java.lang.Class.newInstance(Class.java:275)
at sun.applet.AppletPanel.createApplet(AppletPanel.java:630)
at sun.applet.AppletPanel.runLoader(AppletPanel.java:559)
at sun.applet.AppletPanel.run(AppletPanel.java:300)
at java.lang.Thread.run(Thread.java:566)D:\J2se>
我这样就是对的
<html>
<body>
Here comes my first applet:
<br>
<applet code="test.ShowDate.class" width="650" height="500"></applet>
</body>
</html>源文件:
package test;
import java.awt.*;
import java.util.Date;public class ShowDate extends java.applet.Applet {
String rem = "abcd"; //String title;
Date timeNow = new Date(); Font msgFont = new Font("TimesRoman", Font.ITALIC, 30); String title = getParameter(rem); public void paint(Graphics g) {
g.setFont(msgFont);
g.setColor(Color.blue);
//g.drawString(timeNow.toString(),5,50); g.drawString(title + timeNow.toString(), 5, 50); } public void init() {
title = getParameter(rem);
if (title == null)
title = "";
}
}
// <param name="abcd" value="Hello"></param>
// <param name="rem" value="Yzl32"></param>
//</applet>
import java.awt.*;
import java.util.Date;public class showDate extends java.applet.Applet{
String rem="abcd";
//String title;
Date timeNow=new Date();
Font msgFont=new Font("TimesRoman",Font.ITALIC,30);
String title;//=getParameter(rem); 注释掉,否则报异常,因为applet未初始化
public void paint(Graphics g)
{ g.setFont(msgFont);
g.setColor(Color.blue);
//g.drawString(timeNow.toString(),5,50);
g.drawString(title+timeNow.toString(),5,50);
}
public void init()
{title=getParameter("rem");
if (title==null)
title="";
}
}
// <applet code=showDate.class width=500 height=600 >
// <param name="abcd" value="Hello"></param>
// <param name="rem" value="Yzl32"></param>
//</applet>
import java.awt.*;
import java.util.Date;public class showDate extends java.applet.Applet{
String rem="abcd";
//String title;
Date timeNow=new Date();
Font msgFont=new Font("TimesRoman",Font.ITALIC,30);
String title;//=getParameter(rem); 注释掉,否则报异常,因为applet未初始化
public void paint(Graphics g)
{ g.setFont(msgFont);
g.setColor(Color.blue);
//g.drawString(timeNow.toString(),5,50);
g.drawString(title+timeNow.toString(),5,50);
}
public void init()
{title=getParameter("rem");
if (title==null)
title="";
}
}