帮帮忙，java中提示报错：cannot find symbol。不知道错哪了

帮帮忙，java中提示报错：cannot find symbol。不知道哪里错了
程序肯定没问题的，我在eclipse中可以运行。我在dos下用javac编译的时候出错了。Path环境变量也设置好了（其他程序我都可以编译运行的。。。。）

报错信息如下：

FileInputStream.java:7: cannot find symbol
symbol : constructor FileInputStream(java.lang.String)
location: class FileInputStream
in = new FileInputStream("d:\\file.txt");
^
FileInputStream.java:15: cannot find symbol
symbol : method read()
location: class FileInputStream
while((b = in.read()) != -1){
^
2 errors
import java.io.*;
public class FileInputStream{
public static void main(String []args){
int b = 0;
FileInputStream in = null;
try{
in = new FileInputStream("d:\\file.txt");
} catch(FileNotFoundException e){
System.out.println("file not found!");
System.exit(-1);
}

try{
int num = 0;
while((b = in.read()) != -1){
System.out.println((char)b);
num++;
}
//in.close();
} catch(IOException e){
System.out.println("file read error!");
e.printStackTrace();
System.exit(-1);
}
}
}

------解决方案--------------------

Java code

import java.io.FileInputStream;import java.io.FileNotFoundException;import java.io.IOException;public class Fis {    public static void main(String[] args) {        int b = 0;        FileInputStream in = null;        try {            in = new FileInputStream("c:\\Fis.java");        } catch (FileNotFoundException e) {            System.out.println("file not found!");            e.printStackTrace();            System.exit(-1);        }        try {            int num = 0;            while ((b = in.read()) != -1) {                System.out.println((char) b);                num++;            }            // in.close();        } catch (IOException e) {            System.out.println("file read error!");            e.printStackTrace();            System.exit(-1);        }    }}
------解决方案--------------------
类名不能为FileInputStream，这是java核心类，怎么能重名呢