22.1

java.io.DataInput

THE PACKAGE JAVA.IO

22.1.14

public String readLine() throws IOException

The general contract of

readLine

 is that it reads successive bytes, converting

each byte separately into a character, until it encounters a line terminator or end of

file; the characters read are then returned as a

String

. Note that because this

method processes bytes, it does not support input of the full Unicode character set.

If end of file is encountered before even one byte can be read, then

null

 is

returned. Otherwise, each byte that is read is converted to type

char

 by zero 

extension. If the character

 \n 

 is encountered, it is discarded and reading ceases.

If the character

 \r 

 is encountered, it is discarded and, if the following byte

converts to the character

 \n 

, then that is discarded also; reading then ceases. If

end of file is encountered before either of the characters

 \n 

 and

 \r 

 is encoun 

tered, reading ceases. Once reading has ceased, a

String

 is returned that contains

all the characters read and not discarded, taken in order. Note that every character

in this string will have a value less than

\u0100

, that is,

(char)256

.

22.1.15

public String readUTF() throws IOException

The general contract of

readUTF

 is that it reads a representation of a Unicode

character string encoded in Java modified UTF 8 format; this string of characters

is then returned as a

String

.

First, two bytes are read and used to construct an unsigned 16 bit integer in

exactly the manner of the

readUnsignedShort

 method ( 22.1.8). This integer

value is called the

UTF length

 and specifies the number of additional bytes to be

read. These bytes are then converted to characters by considering them in groups.

The length of each group is computed from the value of the first byte of the group.

The byte following a group, if any, is the first byte of the next group.

If the first byte of a group matches the bit pattern

0xxxxxxx

 (where

x

 means

 may be

0

 or

1

 ), then the group consists of just that byte. The byte is zero 

extended to form a character.

If the first byte of a group matches the bit pattern

110xxxxx

, then the group

consists of that byte

a

 and a second byte

b

. If there is no byte

b

 (because byte

a

was the last of the bytes to be read), or if byte

b

 does not match the bit pattern

10xxxxxx

, then a

UTFDataFormatException

 is thrown. Otherwise, the group is

converted to the character:

(char)(((a & 0x1F) << 6) | (b & 0x3F))

If the first byte of a group matches the bit pattern

1110xxxx

, then the group

consists of that byte

a

 and two more bytes

b

 and

c

. If there is no byte

c

 (because

byte

a

 was one of the last two of the bytes to be read), or either byte

b

 or byte

c

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