下面是 FileInputStream 读取文件的代码片段: File file1=new File(fileName); FileInputStream finput=new FileInputStream(file1); int size=finput.available(); BufferedInputStream buffer1=new BufferedInputStream(finput); byte b[]=new byte[90]; int n=0; while((n=buffer1.read(b))!=-1){ allFilesmess.append(new String(b,0,n)); } buffer1.close(); finput.close(); 除最后一次外,代码中 buffer1.read(b) 每次读取文件的字节数?( )