我有java applet和图形的问题.我试图在Eclipse中运行它,它失败了.
我是java的新手,我希望你能帮助我.
我有两个文件:Say.java和SayWhat.java.
Say.java:
public class Say {
SayWhat word = new SayWhat("Hello World");
}
SayWhat.java:
import java.applet.Applet;
import java.awt.Graphics;
@SuppressWarnings("serial")
public class SayWhat extends Applet {
Graphics g;
String what;
public SayWhat(String what) {
this.what=what;
}
public void paint(Graphics g){
g.drawString(what, 20, 20);
}
}
出现的错误是:
load: SayWhat.class can't be instantiated.
java.lang.InstantiationException: SayWhat
at java.lang.Class.newInstance0(Unknown Source)
at java.lang.Class.newInstance(Unknown Source)
at sun.applet.AppletPanel.createApplet(Unknown Source)
at sun.applet.AppletPanel.runLoader(Unknown Source)
at sun.applet.AppletPanel.run(Unknown Source)
at java.lang.Thread.run(Unknown Source)
你能告诉我我做错了什么吗?
解决方法:
applet需要有一个公共的无参数构造函数(通过具有显式的公共no-arg构造函数,或者根本没有显式构造函数;在后一种情况下,编译器将提供一个公共的无参数构造函数作为默认值).你的类的唯一构造函数需要参数:
public SayWhat(String what) {
因此,如果没有该参数,则无法实例化类,因此不能将其用作applet.