NIOWriteToDisk.java

IOUtil.java

package yelp.dataset.oswego.yelpbackend.services;

import java.io.BufferedOutputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.channels.FileChannel;

import lombok.NoArgsConstructor;
import yelp.dataset.oswego.yelpbackend.algorithms.btree.BusinessBtree;

@NoArgsConstructor
public class IOUtil {
    private final String fileDest = "YOUR PATH TO FILE";

    protected void writeFileWithFileChannel(BusinessBtree businessBtree) throws IOException {
        // Get the file
        FileOutputStream fout = new FileOutputStream(fileDest);
        
        // Register FileChannel to operate read and write
        FileChannel wChannel = fout.getChannel();
        
        // Register ByteBuffer to store message inside a buffer
        ByteBuffer wBuffer = ByteBuffer.allocate(1024);

        String message = "Writing on disk";

        wBuffer.put(message.getBytes());
        /* 
            ByteBuffer::flip() is used to flip BB from "reading from I/O"(put) to "writing to I/O"(get) after a sequence of put
            ByteBuffer::flip() will set the limit of the buffer to current position and reset the position to 0
        */
        wBuffer.flip(); 

        // Acctually write to file from buffer
        wChannel.write(wBuffer);
        
        System.out.println("Success!");

    }


    protected void readRootWithFileChannel(BusinessBtree businessBtree) throws IOException {
        // Get the file
        RandomAccessFile raf = new RandomAccessFile(bTreeRoot, "rw");

        // Register FileChannel to operate read and write
        FileChannel fChannel = raf.getChannel();

        // Allocaate bufferSize 
        int bufferSize = 1024;
        if (bufferSize > fChannel.size()) {
            bufferSize = (int) fChannel.size();
        }
        
        // Register ByteBuffer to store message inside a buffer
        ByteBuffer buff = ByteBuffer.allocate(bufferSize);

        // Read the file to buffer
        fChannel.read(buff);
        
        // Flip the buffer
        buff.flip();

        System.out.println("Reading from buffer = " +new String(buff.array()));

    }

    protected void readRootWithPath(BusinessBtree businessBtree) throws IOException {
        Path path = Paths.get(bTreeRoot);
        List<String> read = Files.readAllLines(path);
        System.out.println("Files.readAllLines(path) = " + read);
        
        Stream<String> lines = Files.lines(path);
        String data = lines.collect(Collectors.joining(" + "));
        lines.close();
        System.out.println("Files.lines(path) = " +data);
        
    }
public class WriteExample {

    public static void main(String... args) throws IOException {
        Path path = Files.createTempFile("test-file", ".txt");
        Files.write(path, "some test content...".getBytes());

        byte[] bytes = Files.readAllBytes(path);
        System.out.println(new String(bytes));
    }
}

public class WriteIterable {

    public static void main(String... args) throws IOException {
        Path path = Files.createTempFile("test-file", ".txt");
        Iterable<String> iterable = Arrays.asList("line1", "line2");
        Files.write(path, iterable);

        byte[] bytes = Files.readAllBytes(path);
        System.out.println(new String(bytes));

    }
}