BufferedReader类中的方法readLine()为读取一行字符串，DataInputStream类中的方法readUTF()的返回值为String,也为字符串，那readUTF()读取的字符串到底能有多长呀？
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- Java code
/** * Reads from the * stream <code>in</code> a representation * of a Unicode character string encoded in * <a href="DataInput.html#modified-utf-8">modified UTF-8</a> format; * this string of characters is then returned as a <code>String</code>. * The details of the modified UTF-8 representation * are exactly the same as for the <code>readUTF</code> * method of <code>DataInput</code>. * * @param in a data input stream. * @return a Unicode string. * @exception EOFException if the input stream reaches the end * before all the bytes. * @exception IOException the stream has been closed and the contained * input stream does not support reading after close, or * another I/O error occurs. * @exception UTFDataFormatException if the bytes do not represent a * valid modified UTF-8 encoding of a Unicode string. * @see java.io.DataInputStream#readUnsignedShort() */ public final static String readUTF(DataInput in) throws IOException { int utflen = in.readUnsignedShort(); 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); while (count < utflen) { c = (int) bytearr[count] & 0xff; if (c > 127) break; count++; chararr[chararr_count++]=(char)c; } while (count < utflen) { c = (int) bytearr[count] & 0xff; switch (c >> 4) { case 0: case 1: case 2: case 3: case 4: case 5: case 6: case 7: /* 0xxxxxxx*/ count++; chararr[chararr_count++]=(char)c; break; case 12: case 13: /* 110x xxxx 10xx xxxx*/ count += 2; if (count > utflen) throw new UTFDataFormatException( "malformed input: partial character at end"); char2 = (int) bytearr[count-1]; if ((char2 & 0xC0) != 0x80) throw new UTFDataFormatException( "malformed input around byte " + count); chararr[chararr_count++]=(char)(((c & 0x1F) << 6) | (char2 & 0x3F)); break; case 14: /* 1110 xxxx 10xx xxxx 10xx xxxx */ count += 3; if (count > utflen) throw new UTFDataFormatException( "malformed input: partial character at end"); char2 = (int) bytearr[count-2]; char3 = (int) bytearr[count-1]; if (((char2 & 0xC0) != 0x80) || ((char3 & 0xC0) != 0x80)) throw new UTFDataFormatException( "malformed input around byte " + (count-1)); chararr[chararr_count++]=(char)(((c & 0x0F) << 12) | ((char2 & 0x3F) << 6) | ((char3 & 0x3F) << 0)); break; default: /* 10xx xxxx, 1111 xxxx */ throw new UTFDataFormatException( "malformed input around byte " + count); } } // The number of chars produced may be less than utflen return new String(chararr, 0, chararr_count); }