Java.io.RandomAccessFile Class provides a way to random access files using reading and writing operations. It works like an array of byte storted in the File.
Declaration :
public class RandomAccessFile
extends Object
implements DataOutput, DataInput, Closeable
Methods of RandomAccessFile Class :
- read() : java.io.RandomAccessFile.read() reads byte of data from file. The byte is returned as an integer in the range 0-255
Syntax : public int read() Parameters : -------- Return : reads byte of data from file, -1 if end of file is reached.
- read(byte[] b) java.io.RandomAccessFile.read(byte[] b) reads bytes upto b.length from the buffer.
Syntax : public int read(byte[] b) Parameters : b : buffer to be read Return : byte of data from file upto b.length, -1 if end of file is reached.
- read((byte[] b, int offset, int len) : java.io.RandomAccessFile.read((byte[] b, int offset, int len) reads bytes initialising from offset position upto b.length from the buffer.
Syntax : public int read(byte[] b, int offset, int len) Parameters : b : buffer to read offset : starting position to read len : max no of bytes to read Return : reads bytes initialising from offset position upto b.length from the buffer.
- readBoolean() : java.io.RandomAccessFile.readBoolean() reads a boolean from the file.
Syntax : public final boolean readBoolean() Parameters : ------ Return : boolean value
- readByte() : java.io.RandomAccessFile.readByte() reads a signed eight-bit value from file, start reading from the File Pointer.
Syntax : public final byte readByte() Parameters : ------- Return : signed eight-bit value from file
- readChar() : java.io.RandomAccessFile.readChar() reads a character from the file, start reading from the File Pointer.
Syntax : public final char readChar() Parameters : ------- Return : character from the file.
- readDouble() : java.io.RandomAccessFile.readDouble() reads a double value from the file, start reading from the File Pointer.
Syntax : public final double readDouble() Parameters : ------ Return : reads a double value from the file.
- readFloat() : java.io.RandomAccessFile.readFloat() reads a float value from the file, start reading from the File Pointer.
Syntax : public final double readFloat() Parameters : ------ Return : reads a float value from the file.
- readFully(byte[] b) : java.io.RandomAccessFile.readFully(byte[] b) reads bytes upto b.length from the buffer, start reading from the File Pointer.
Syntax : public final void readFully(byte[] b) Parameters : b : buffer to be read Return : reads bytes initialising from offset position upto b.length from the buffer
- readInt() : java.io.RandomAccessFile.readInt() reads a signed 4 bytes integer from the file, start reading from the File Pointer.
Syntax : reads a signed 4 bytes integer from the file Parameters : ----- Return : reads a signed 4 bytes integer from the file
- readFully(byte[] b, int offset, int len) : java.io.RandomAccessFile.readFully(byte[] b, int offset, int len) reads bytes initialising from offset position upto b.length from the buffer, start reading from the File Pointer.
Syntax : public final void readFully(byte[] b, int offset, int len) Parameters : b : buffer to read offset : starting position to read len : max no of bytes to read Return : bytes initialising from offset position upto b.length from the buffer
- readLong() : java.io.RandomAccessFile.readLong() reads a signed 64 bit integer from the file, start reading from the File Pointer.
Syntax : public final long readLong() Parameters : ------- Return : signed 64 bit integer from the file
// Java Program illustrating use of io.RandomAccessFile class methods// read(), read(byte[] b), readBoolean(), readByte(), readInt()// readFully(byte[] b, int off, int len), readFully(), readFloat()// readChar(), readDouble(), import java.io.*;public class NewClass{ public static void main(String[] args) { try { double d = 1.5; float f = 14.56f; // Creating a new RandomAccessFile - "GEEK" RandomAccessFile geek = new RandomAccessFile("GEEK.txt", "rw"); // Writing to file geek.writeUTF("Hello Geeks For Geeks"); // File Pointer at index position - 0 geek.seek(0); // read() method : System.out.println("Use of read() method : " + geek.read()); geek.seek(0); byte[] b = {1, 2, 3}; // Use of .read(byte[] b) method : System.out.println("Use of .read(byte[] b) : " + geek.read(b)); // readBoolean() method : System.out.println("Use of readBoolean() : " + geek.readBoolean()); // readByte() method : System.out.println("Use of readByte() : " + geek.readByte()); geek.writeChar('c'); geek.seek(0); // readChar() : System.out.println("Use of readChar() : " + geek.readChar()); geek.seek(0); geek.writeDouble(d); geek.seek(0); // read double System.out.println("Use of readDouble() : " + geek.readDouble()); geek.seek(0); geek.writeFloat(f); geek.seek(0); // readFloat() : System.out.println("Use of readFloat() : " + geek.readFloat()); geek.seek(0); // Create array upto geek.length byte[] arr = new byte[(int) geek.length()]; // readFully() : geek.readFully(arr); String str1 = new String(arr); System.out.println("Use of readFully() : " + str1); geek.seek(0); // readFully(byte[] b, int off, int len) : geek.readFully(arr, 0, 8); String str2 = new String(arr); System.out.println("Use of readFully(byte[] b, int off, int len) : " + str2); } catch (IOException ex) { System.out.println("Something went Wrong"); ex.printStackTrace(); } }} |
Output :
Use of read() method : 0 Use of .read(byte[] b) : 3 Use of readBoolean() : true Use of readByte() : 108 Use of readChar() : c Use of readDouble() : 1.5 Use of readFloat() : 14.56 Use of readFully() : Geeks For Geeks Use of readFully(byte[] b, int off, int len) : Geeks For Geeks
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