How To Read/Write From Randomaccessfile Inward Java

Random access file is a exceptional variety of file inwards Java which allows non-sequential or random access to whatsoever place inwards file. This agency yous don't involve to start from 1st trouble if yous wish to read trouble disclose 10, yous tin straight piece of employment to trouble 10 in addition to read. It's similar to array information structure, Just similar yous tin access whatsoever chemical ingredient inwards array past times index yous tin read whatsoever content from file past times using file pointer. Influenza A virus subtype H5N1 random access file genuinely behaves similar a large array of bytes stored inwards file organization in addition to that's why its really useful for depression latency applications which needs or hence variety of persistence e.g. inwards forepart component trading application in addition to FIX Engine, yous tin purpose random access file to shop FIX sequence numbers or all opened upwards orders. This volition live handy when yous recover from crash in addition to yous involve to build your inwards retention cache to the soil simply earlier the crash.  RandomAccessFile provides yous mightiness to read in addition to write into whatsoever random access file. When yous read content from file, yous start amongst electrical current place of file pointer in addition to pointer is moved frontward past times how many bytes are read. Similarly when yous write information into random access file, it starts writing from electrical current place of file pointer in addition to and hence advances the file pointer past times disclose of files written. Random access is achieved past times setting file pointer to whatsoever arbitrary place using seek() method. You tin every bit good acquire electrical current place past times calling getFilePointer() method. There are 2 top dog ways to read in addition to write information into RandomAccessFile, either yous tin purpose Channel e.g. SeekableByteChannel in addition to ByteBuffer cast from Java NIO, this allows yous to read information from file to byte buffer or write information from byte buffer to random access file. Alternatively yous tin every bit good purpose diverse read() in addition to write() method from RandomAccessFile e.g readBoolean(), readInt(), readLine() or readUTF().  This is a 2 component Java IO tutorial, inwards this component nosotros volition larn how to read in addition to write String from RandomAccess file inwards Java without using Java NIO channels in addition to inwards adjacent component nosotros volition larn how to read bytes using ByteBuffer in addition to Channel API. .

How to Read/Write into Random Access File

In social club to write information into random access file, yous kickoff involve to practice an illustration of RandomAccessFile cast inwards read in addition to write mode. You tin practice this past times passing "rw" every bit trend to the constructor. Once yous done that yous tin either purpose SeekableByteChannel or seek() method to gear upwards the pointer to a place where yous wish to write data. You tin either writes bytes using ByteBuffer in addition to Java NIO Channel API or yous tin write int, float, String or whatsoever other Java information type past times using respective writeInt(), writeFloat() in addition to writeUTF() methods. All these methods are defined inwards java.io.RandomAccessFile cast inwards Java IO package. When yous write information which exceeds electrical current size of file caused random access file to live extended. For reading information from random access, yous tin either opened upwards the file into read exclusively mode or read write mode. Just similar writing, yous tin every bit good perform reading either past times using Channel API in addition to ByteBuffer cast ( yous should if yous are using Java NIO ) or traditional methods defined inwards RandomAccessFile inwards Java. Just similar yous receive got unlike write method to write unlike information types yous every bit good receive got corresponding read methods to read them back. In social club to read from a random location, yous tin purpose seek() method to gear upwards the file pointer to a item place inwards file. By the way, if halt of file is reached earlier your plan read desired disclose of bytes, an EOFException volition live thrown. If whatsoever byte cannot live read due to whatsoever other argue in addition to hence IOException volition live thrown.

RandomAccessFile Example inwards Java

Following is our sample Java plan to demonstrate how yous tin yous read or write String from a RandomAccessFile. The file elevate is "sample.store" which volition live created inwards electrical current directory, commonly inwards your projection directory if yous are using Eclipse IDE. We receive got 2 utility method to read String from random access file in addition to write string into file, both method takes an int place to demonstrate random read in addition to random write operation. In social club to write in addition to read String, nosotros volition live using writeUTF() in addition to readUTF() method, which reads String inwards modified UTF-8 format. Though, inwards this program, I receive got unopen file inwards endeavor block, yous should e'er practice that inwards a lastly block amongst additional endeavor block, or improve purpose try-with-resource disputation from Java 7. I volition demo yous how yous tin practice that inwards adjacent component of this tutorial when nosotros volition larn reading in addition to writing byte arrays using ByteBuffer in addition to SeekableByteChannel class.

import java.io.FileNotFoundException; import java.io.IOException; import java.io.RandomAccessFile; import java.nio.ByteBuffer; import java.nio.channels.FileChannel;  /** * Java Program to read in addition to write UTF String on RandomAccessFile inwards Java. * * @author Javin Paul */ public class RandomAccessFileDemo{      public static void main(String args[]) {          String information = "KitKat (4.4 - 4.4.2)";         writeToRandomAccessFile("sample.store", 100, data);         System.out.println("String written into RandomAccessFile from Java Program : " + data);          String fromFile = readFromRandomAccessFile("sample.store", 100);         System.out.println("String read from RandomAccessFile inwards Java : " + fromFile);      }      /*      * Utility method to read from RandomAccessFile inwards Java      */     public static String readFromRandomAccessFile(String file, int position) {         String tape = null;         try {             RandomAccessFile fileStore = new RandomAccessFile(file, "rw");              // moves file pointer to seat specified             fileStore.seek(position);              // reading String from RandomAccessFile             tape = fileStore.readUTF();              fileStore.close();          } catch (IOException e) {             e.printStackTrace();         }          return record;     }     /*     * Utility method for writing into RandomAccessFile inwards Java     */       public static void writeToRandomAccessFile(String file, int position, String record) {         try {             RandomAccessFile fileStore = new RandomAccessFile(file, "rw");              // moves file pointer to seat specified             fileStore.seek(position);              // writing String to RandomAccessFile             fileStore.writeUTF(record);              fileStore.close();          } catch (IOException e) {             e.printStackTrace();         }     } }    Output: String written into RandomAccessFile from Java Program : KitKat (4.4 - 4.4.2) String read from RandomAccessFile inwards Java : KitKat (4.4 - 4.4.2)

That's all nigh how to read in addition to write from RandomAccessFile inwards Java.  You would live surprised that this cast is available from JDK 1.0 itself.  It is indeed a really useful cast from traditional Java IO API, which was exclusively rootage of doing high speed IO earlier Java NIO came amongst memory mapped file.

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