java file write performance

java-file-write-performance.java

/**
 * http://stackoverflow.com/questions/1062113/fastest-way-to-write-huge-data-in-text-file-java
 * 
 * I have to write huge data in text[csv] file. I used BufferedWriter to write the data and it 
 * took around 40 secs to write 174 mb of data. Is this the fastest speed java can offer?
 * bufferedWriter = new BufferedWriter ( new FileWriter ( "fileName.csv" ) );
 * 
 * You might try removing the BufferedWriter and just using the FileWriter directly. On a modern system 
 * there's a good chance you're just writing to the drive's cache memory anyway.
 * It takes me in the range of 4-5 seconds to write 175MB (4 million strings) -- this is on a dual-core 2.4GHz Dell 
 * running Windows XP with an 80GB, 7200-RPM Hitachi disk.
 */

import java.io.BufferedWriter;
import java.io.File;
import java.io.FileWriter;
import java.io.IOException;
import java.io.Writer;
import java.util.ArrayList;
import java.util.List;

public class FileWritingPerfTest {


private static final int ITERATIONS = 5;
private static final double MEG = (Math.pow(1024, 2));
private static final int RECORD_COUNT = 4000000;
private static final String RECORD = "Help I am trapped in a fortune cookie factory\n";
private static final int RECSIZE = RECORD.getBytes().length;

public static void main(String[] args) throws Exception {
    List<String> records = new ArrayList<String>(RECORD_COUNT);
    int size = 0;
    for (int i = 0; i < RECORD_COUNT; i++) {
        records.add(RECORD);
        size += RECSIZE;
    }
    System.out.println(records.size() + " 'records'");
    System.out.println(size / MEG + " MB");

    for (int i = 0; i < ITERATIONS; i++) {
        System.out.println("\nIteration " + i);

        writeRaw(records);
        writeBuffered(records, 8192);
        writeBuffered(records, (int) MEG);
        writeBuffered(records, 4 * (int) MEG);
    }
}

private static void writeRaw(List<String> records) throws IOException {
    File file = File.createTempFile("foo", ".txt");
    try {
        FileWriter writer = new FileWriter(file);
        System.out.print("Writing raw... ");
        write(records, writer);
    } finally {
        // comment this out if you want to inspect the files afterward
        file.delete();
    }
}

private static void writeBuffered(List<String> records, int bufSize) throws IOException {
    File file = File.createTempFile("foo", ".txt");
    try {
        FileWriter writer = new FileWriter(file);
        BufferedWriter bufferedWriter = new BufferedWriter(writer, bufSize);

        System.out.print("Writing buffered (buffer size: " + bufSize + ")... ");
        write(records, bufferedWriter);
    } finally {
        // comment this out if you want to inspect the files afterward
        file.delete();
    }
}

private static void write(List<String> records, Writer writer) throws IOException {
    long start = System.currentTimeMillis();
    for (String record: records) {
        writer.write(record);
    }
    writer.flush();
    writer.close();
    long end = System.currentTimeMillis();
    System.out.println((end - start) / 1000f + " seconds");
}
}