import java.io.*;
public class FileInputStreamTest
{
public static void main(String[] args) throws IOException
{
// 创建字节输入流
FileInputStream fis = new FileInputStream(
"FilenameFilterTest.java");
// 创建一个长度为1024的“竹筒”
byte[] bbuf = new byte[1024];
// 用于保存实际读取的字节数
int hasRead = 0;
// 使用循环来重复“取水”过程
while ((hasRead = fis.read(bbuf)) > 0 )
{
// 取出“竹筒”中水滴（字节），将字节数组转换成字符串输入！
System.out.print(new String(bbuf , 0 , hasRead ));
}
// 关闭文件输入流，放在finally块里更安全
fis.close();
}
}
Exception in thread "main" java.io.FileNotFoundException: .\FilenameFilterTest.java (系统找不到指定的文件。)
at java.base/java.io.FileInputStream.open0(Native Method)
at java.base/java.io.FileInputStream.open(Unknown Source)
at java.base/java.io.FileInputStream.(Unknown Source)
at java.base/java.io.FileInputStream.(Unknown Source)
at FileInputStreamTest.main(FileInputStreamTest.java:8)
文件是存在的，换成其他文件或者绝对路径还是报错
