关于FilterInputStream的使用的问题：

[kops]

请看我自己写的一段代码：
import java.io.*;

public class FilterInputStreamDemo {
FilterInputStream fis=new FilterInputStream(new FileInputStream(“c:/classes/class1.java”));

public static void main(String args[])throws IOException {
System.out.println("Available:"+fis.available());
StringBuffer sb=new StringBuffer();
for(int i=0;i<10;i++){
int c=fis.read();
sb.append((char)c);
}
System.out.println(sb.toString());
}
}

本来想用 FilterInputStream()作为FilterInputSteam的输入参数，但出现错误：
FilterInputStreamDemo.java:4: FilterInputStream(java.io.InputStream) has protect
ed access in java.io.FilterInputStream
FilterInputStream fis=new FilterInputStream(new FileInputStream("C:/clas
ses/Class1.java"));
^
于是我把FilterInputStream()的参数改为：System.in，结果同样出错，请问怎么解决？
一个类的参数是否能用他的子类呢？比如FilterInputStream(InputStream)参数是InputStream,能否用同样是InputStream的FileInputStream作为参数呢？如果不能，又能以什么作为InputStream类的参数呢？
FilterInputStream作为过滤流类，怎么过滤法呢？他具体有什么用呢？

[wks9527]

FileInputStream 和　FilterInputStream　都继承自InputStream，
它们是兄弟关系
在FilterInputStream中的构造子是这样定义的：
protected FilterInputStream(InputStream in)，它声明为protected.
另外，FilterInputStream的描述是这样的：
A FilterInputStream contains some other input stream, which it uses as
its basic source of data, possibly transforming the data along the way or providing additional functionality. The class FilterInputStream
itself simply overrides all methods of　InputStream with versions that
pass all requests to the contained input　stream. Subclasses of FilterInputStream
may further override some of these methods and may also provide additional methods and fields.
并不是你说的文件过虑类，文件过滤类应该继承javax.swing.filechooser.FileFilter

[kops]

那么这段程序可以怎么改呢？

[teddy_huang]

FilterInputStream fis=new FilterInputStream(new FileInputStream(“c:/classes/class1.java”));
改成
FileInputStream fis = new FileInputStream(“c:/classes/class1.java”);

[kops]

我是想用FilterInputStream