Buferinis simbolių įvesties srautas, kuris seka eilučių numerius. Ši klasė apibrėžia metodus setLineNumber(int) ir getLineNumber(), skirtus atitinkamai nustatyti ir gauti dabartinės eilutės numerį.
Pagal numatytuosius nustatymus eilučių numeracija prasideda nuo 0. Nuskaitant duomenis šis skaičius didėja ties kiekvienu eilutės užbaigimu ir gali būti pakeistas iškvietus setLineNumber(int).
Tačiau atkreipkite dėmesį, kad setLineNumber(int) iš tikrųjų nekeičia dabartinės padėties sraute; ji pakeičia tik reikšmę, kurią grąžins getLineNumber().
Laikoma, kad eilutė baigta bet kuriuo iš eilutės padavimo („n“), vežimo grįžimo („r“) arba vežimo grįžimo, po kurio iškart seka eilutės pervedimas.
Konstruktoriai:
LineNumberReader (skaitytojas):
Sukurkite naują eilučių numeravimo skaitytuvą naudodami numatytąjį įvesties buferio dydį.
LineNumberReader(Reader int sz) :
Sukurkite naują eilučių numeravimo skaitytuvą, nuskaitantį simbolius nurodyto dydžio buferyje. Metodai:
int getLineNumber() :
Get the current line number.
Syntax : public int getLineNumber() Returns: The current line number
negaliojantis ženklas (int readAheadLimit):
Mark the present position in the stream.Subsequent calls to reset() will attempt to reposition the stream to this point and will also reset the line number appropriately.
Syntax : public void mark(int readAheadLimit) throws IOException Parameters: readAheadLimit - Limit on the number of characters that may be read while still preserving the mark. After reading this many characters attempting to reset the stream may fail. Throws: IOException
int read() :
Read a single character.Line terminators are compressed into single newline ('n') characters. Whenever a line terminator is read the current line number is incremented.
Syntax : public int read() throws IOException Returns: The character read or -1 if the end of the stream has been reached Throws: IOException
int read(char[] cbuf int off int len):
Read characters into a portion of an array.Whenever a line terminator is read the current line number is incremented.
Syntax : public int read(char[] cbuf int off int len) throws IOException Parameters: cbuf - Destination buffer off - Offset at which to start storing characters len - Maximum number of characters to read Returns: The number of bytes read or -1 if the end of the stream has already been reached Throws: IOException
Eilutė readLine() :
Read a line of text.Whenever a line terminator is read the current line number is incremented.
Syntax : public String readLine() throws IOException Returns: A String containing the contents of the line not including any line termination characters or null if the end of the stream has been reached Throws: IOException
negaliojantis atstatymas () :
Reset the stream to the most recent mark.
Syntax : public void reset() throws IOException Throws: IOException
void setLineNumber(int lineNumber) :
Set the current line number.
Syntax : public void setLineNumber(int lineNumber) Parameters: lineNumber - An int specifying the line number
ilgas praleidimas (ilgas n):
Skip characters.
Syntax : public long skip(long n) throws IOException Parameters: n - The number of characters to skip Returns: The number of characters actually skipped Throws: IOException IllegalArgumentException
Programa: Java
//Java program demonstrating LineNumberReader methodsimportjava.io.FileReader;importjava.io.IOException;importjava.io.LineNumberReader;classLineNumberReaderDemo{publicstaticvoidmain(String[]args)throwsIOException{FileReaderfr=newFileReader('file.txt');LineNumberReaderlnr=newLineNumberReader(fr);charc[]=newchar[20];//illustrating setLineNumber()lnr.setLineNumber(0);//illustrating setSystem.out.println(lnr.getLineNumber());//illustrating markSupported() methodif(lnr.markSupported()){System.out.println('mark() method is supported');//illustrating mark methodlnr.mark(100);}/*File Contents * This is first line this is second line This is third line *///skipping 19 characterslnr.skip(19);//illustrating ready() methodif(lnr.ready()){//illustrating readLine() methodSystem.out.println(lnr.readLine());//illustrating read(char c[]int offint len)lnr.read(c);for(inti=0;i<20;i++){System.out.print(c[i]);}//illustrating reset() methodlnr.reset();for(inti=0;i<18;i++){//illustrating read() methodSystem.out.print((char)lnr.read());}intch;//illustrating read() methodSystem.out.println(lnr.readLine());while((ch=lnr.read())==1)System.out.print((char)ch);}//close the streamlnr.close();}}
Išvestis:
0 mark() method is supported this is second line This is third line This is first line