如果想用字節流讀完文件 壹般用壹個字節數組的緩沖區 比如200
byte[] buffer = new byte[200];//創建字節數組
int length = 0;
while(-1 != (length = is.read(buffer, 0, buffer.length))){
String str = new String(buffer,0,length);
System.out.println(str);
}