DataInputStream.readUTF能读取的数据不是一般的数据，实际使用的也不多，一般会配合DataOutStream.writeUTF配合使用，一般的字符串不要使用readUTF读取，否则就会报EOFException的异常，至于为什么会出现这个问题，看下DataInputStream.readUTF以及DataOutStream.writeUTF的源码来解释下：
public final static String readUTF(DataInput in) throws IOException { int utflen = in.readUnsignedShort(); //读取字符串长度，所以readUTF能读取的字符串前面有两个字节是真正要读取的字符串的长度 byte[] bytearr = null; char[] chararr = null; if (in instanceof DataInputStream) { DataInputStream dis = (DataInputStream)in; if (dis.bytearr.length < utflen){ dis.bytearr = new byte[utflen*2]; dis.chararr = new char[utflen*2]; } chararr = dis.chararr; bytearr = dis.bytearr; } else { bytearr = new byte[utflen]; chararr = new char[utflen]; }
int c, char2, char3; int count = 0; int chararr_count=0;
in.readFully(bytearr, 0, utflen);
static int writeUTF(String str, DataOutput out) throws IOException { int strlen = str.length(); int utflen = 0; int c, count = 0;
byte[] bytearr = null; if (out instanceof DataOutputStream) { DataOutputStream dos = (DataOutputStream)out; if(dos.bytearr == null || (dos.bytearr.length < (utflen+2))) dos.bytearr = new byte[(utflen*2) + 2]; bytearr = dos.bytearr; } else { bytearr = new byte[utflen+2]; }
out.write(bytearr, 0, utflen+2); //实际写入数据时会在前两个字节写入字符串长度