I/O Programming - JAVA Programming for Engineers - page 175

codingavalueintherange-128to127.Themaximumpositivevaluefora
byteoperandis127.Therefore,thevalues128through255arenotlegal.

Programmersnote:

Two'scomplementrepresentationsareanencodingschemeforsigned
binaryintegersdesignedtofacilitatemachinearithmetic.Thevalueof
thetwo'scomplementisthedifferencebetweenthenumberandthe
nextintegerpoweroftwothatisgreaterthanthenumber.Asimpleway
ofcalculatingthetwo'scomplementofabinarynumberisnegatingall
thedigitsandaddingonetotheresult.Anadditionaladvantageoftwo's
complementrepresentationsisthatthereisnoencodingfornegative
zero.

OneofthedifficultiesofJavastreamoperationsisthatthebytedata
typeisnotconvenient.Whilemanyofthemethodsinthestreamclasses
aredocumentedtoacceptorreturnbytearguments,inreality,theyoperate
onintdata.ThemainreasonisthatthereisnobyteliteralsinJava,al-
thoughthecompilersometimesmakesautomaticassignmentconversions;
forexample:

byte val1 = 22; // Valid assignment

byte val2 = 44; // Valid assignment

however,
byte val3 = val1 + val2; // Illegal. Requires type cast
byte val4=1=3;

//Illegal. Requires type cast

Thesmallrangeofthebytedatatypeexplainswhytheyareoftencon-
vertedtointincalculations.Laterthecalculatedvaluesaretypecastback
intothebyteformat.Thismeansthatalthoughastreamisdefinedtooper-
ateonbytedata,internalprocessingofnumericdatabystring-based
classesisoftendoneonintdatatypes.

JavaInputStreamclass
TheInputStreamclass,locatedinthejava.iopackage,istheabstractclasson
whichallinputstreamsarebased.Theclasscontainsseveralmethodsasso-
ciatedwithinputstreams,includingreadingdatafromthestream,closing
andflushingstreams,andcheckinghowmanybytesofdataareavailable. Ta-
ble18-2 , onthefollowingpage,liststhemethodsoftheInputStreamclass.

Themethodread()isdesignedtoobtainbytedatafromtheinput
stream.In Table18-2 youcanseeread()isoverloadedinthreedifferentim-
plementations:read(),read(byte[]b),andread(byte[]b,intoff,intlen).