How To Read/Write From Randomaccessfile Inwards Java

Random access file is a particular variety of file inwards Java which allows non-sequential or random access to whatsoever place inwards file. This agency y'all don't ask to start from 1st draw of piece of occupation if y'all wish to read draw of piece of occupation break 10, y'all tin give the sack straight cash inwards one's chips to draw of piece of occupation 10 together with read. It's similar to array information structure, Just similar y'all tin give the sack access whatsoever chemical constituent inwards array yesteryear index y'all tin give the sack read whatsoever content from file yesteryear using file pointer. H5N1 random access file genuinely behaves similar a large array of bytes stored inwards file organization together with that's why its really useful for depression latency applications which needs approximately variety of persistence e.g. inwards forepart purpose trading application together with FIX Engine, y'all tin give the sack usage random access file to shop FIX sequence numbers or all opened upward orders. This volition live handy when y'all recover from crash together with y'all ask to build your inwards retentiveness cache to the field only earlier the crash.  RandomAccessFile provides y'all mightiness to read together with write into whatsoever random access file. When y'all read content from file, y'all start amongst electrical flow place of file pointer together with pointer is moved frontward yesteryear how many bytes are read. Similarly when y'all write information into random access file, it starts writing from electrical flow place of file pointer together with therefore advances the file pointer yesteryear break of files written. Random access is achieved yesteryear setting file pointer to whatsoever arbitrary place using seek() method. You tin give the sack too acquire electrical flow place yesteryear calling getFilePointer() method. There are 2 original ways to read together with write information into RandomAccessFile, either y'all tin give the sack usage Channel e.g. SeekableByteChannel together with ByteBuffer shape from Java NIO, this allows y'all to read information from file to byte buffer or write information from byte buffer to random access file. Alternatively y'all tin give the sack too usage diverse read() together with write() method from RandomAccessFile e.g readBoolean(), readInt(), readLine() or readUTF().  This is a 2 part Java IO tutorial, inwards this part nosotros volition larn how to read together with write String from RandomAccess file inwards Java without using Java NIO channels together with inwards side yesteryear side part nosotros volition larn how to read bytes using ByteBuffer together with Channel API. .

How to Read/Write into Random Access File

In gild to write information into random access file, y'all start ask to exercise an illustration of RandomAccessFile shape inwards read together with write mode. You tin give the sack exercise this yesteryear passing "rw" every bit trend to the constructor. Once y'all done that y'all tin give the sack either usage SeekableByteChannel or seek() method to laid upward the pointer to a place where y'all wish to write data. You tin give the sack either writes bytes using ByteBuffer together with Java NIO Channel API or y'all tin give the sack write int, float, String or whatsoever other Java information type yesteryear using respective writeInt(), writeFloat() together with writeUTF() methods. All these methods are defined inwards java.io.RandomAccessFile shape inwards Java IO package. When y'all write information which exceeds electrical flow size of file caused random access file to live extended. For reading information from random access, y'all tin give the sack either opened upward the file into read solely mode or read write mode. Just similar writing, y'all tin give the sack too perform reading either yesteryear using Channel API together with ByteBuffer shape ( y'all should if y'all are using Java NIO ) or traditional methods defined inwards RandomAccessFile inwards Java. Just similar y'all direct maintain dissimilar write method to write dissimilar information types y'all too direct maintain corresponding read methods to read them back. In gild to read from a random location, y'all tin give the sack usage seek() method to laid upward the file pointer to a item place inwards file. By the way, if goal of file is reached earlier your plan read desired break of bytes, an EOFException volition live thrown. If whatsoever byte cannot live read due to whatsoever other argue therefore IOException volition live thrown.

RandomAccessFile Example inwards Java

Following is our sample Java plan to demonstrate how y'all tin give the sack y'all read or write String from a RandomAccessFile. The file advert is "sample.store" which volition live created inwards electrical flow directory, unremarkably inwards your projection directory if y'all are using Eclipse IDE. We direct maintain 2 utility method to read String from random access file together with write string into file, both method takes an int place to demonstrate random read together with random write operation. In gild to write together with read String, nosotros volition live using writeUTF() together with readUTF() method, which reads String inwards modified UTF-8 format. Though, inwards this program, I direct maintain unopen file inwards attempt block, y'all should ever exercise that inwards a lastly block amongst additional attempt block, or meliorate usage try-with-resource disputation from Java 7. I volition demonstrate y'all how y'all tin give the sack exercise that inwards side yesteryear side part of this tutorial when nosotros volition larn reading together with writing byte arrays using ByteBuffer together with 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 together with 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 most how to read together with write from RandomAccessFile inwards Java.  You would live surprised that this shape is available from JDK 1.0 itself.  It is indeed a really useful shape from traditional Java IO API, which was solely root of doing high speed IO earlier Java NIO came amongst memory mapped file.

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