In this tutorial we are going to see how use RandomAccessFile in order to to read an write data to a File in random positions. The RandomAccessFile class treats the file as an array of Bytes. And you can write your data in any position of the Array. To do that, it uses a pointer that holds the current position (you can think of that pointer like a cursor in a text editor…).
RandomAccessFile does that using :
getFilePointer()to get the current position of the pointerseek(int )to set the position of the pointerread(byte[] b)to reads up tob.lengthbytes of data from the file into an array of byteswrite(byte[] b)to writeb.lengthbytes from the specified byte array to the file, starting at the current file pointer
Take a look at the code :
package com.javacodegeeks.java.core;
import java.io.IOException;
import java.io.RandomAccessFile;
public class RandomAccessFileEx {
static final String FILEPATH = "C:/Users/nikos7/Desktop/input.txt";
public static void main(String[] args) {
try {
System.out.println(new String(readFromFile(FILEPATH, 150, 23)));
writeToFile(FILEPATH, "JavaCodeGeeks Rocks!", 22);
} catch (IOException e) {
e.printStackTrace();
}
}
private static byte[] readFromFile(String filePath, int position, int size)
throws IOException {
RandomAccessFile file = new RandomAccessFile(filePath, "r");
file.seek(position);
byte[] bytes = new byte[size];
file.read(bytes);
file.close();
return bytes;
}
private static void writeToFile(String filePath, String data, int position)
throws IOException {
RandomAccessFile file = new RandomAccessFile(filePath, "rw");
file.seek(position);
file.write(data.getBytes());
file.close();
}
}
This was en example of Java RandomAccessFile.
Nice example but how do you create a RandomAccessFile with the android Storage Access Framework(SAF) using DocumentContracts etc