使用RandomAccessFile进行文件的读写

RandomAccessFile raf = new RandomAccessFile("test.txt","r");

byte[] buf = new byte[40];
int len = raf.read(buf);
System.out.println("读取的字节>>>> "+len);
System.out.println(Arrays.toString(buf));

String str = new String(buf);
System.out.println(str);

str = new String(buf,"UTF-8");
System.out.println(str);
System.out.println(str.length());

str = new String(buf,0,len,"UTF-8");
System.out.println(str);
raf.close();

RandomAccessFile raf = null;
try {

raf = new RandomAccessFile("test.txt","rw") ;  // 读写文件是按照字节为单位进行的

System.out.println(Integer.toBinaryString((int)'a'));

raf.write(97);
raf.write(3);
raf.writeBytes("a");
raf.writeChars("  I ma");

} catch (Exception e) {
e.printStackTrace();
}finally{
if(raf != null){
raf.close();
}
}