Is Using Direct FileWriter Faster Than BufferedWriter for Writing Large Text Files in Java?

Improving Write Speed for Large Data in Text Files

When dealing with substantial datasets, optimizing write performance for text files is crucial. While using BufferedWriter is a common technique, it may not always provide the desired efficiency. This article explores alternative approaches to accelerate data writing in Java.

Direct FileWriter Usage

The BufferedWriter offers a buffered approach to writing data. However, bypassing this buffer can potentially improve speed on modern systems, where writes are typically cached to the drive's memory. To achieve this, simply replace BufferedWriter with FileWriter in your code.

Empirical Testing

Empirical testing reveals significant performance gains by using a direct FileWriter. For a dataset of 175MB (4 million strings), writing without BufferedWriter took approximately 4-5 seconds on a dual-core system. This represents a substantial improvement over the initial 40-second duration observed with BufferedWriter.

Write Performance Measurement

To provide empirical evidence, the following code block showcases a performance test that compares the writing times using BufferedWriter with varying buffer sizes and a direct FileWriter:

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 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 {
            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 {
            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.close(); 
        long end = System.currentTimeMillis();
        System.out.println((end - start) / 1000f + " seconds");
    }

    // ...
}

Conclusion

The experimental results demonstrate that using a direct FileWriter can significantly enhance write performance for large datasets. This technique is particularly beneficial for scenarios where writing speed is critical. By leveraging these findings, developers can optimize their code to efficiently handle large volumes of data in text files.

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