在文本文件Java中写入大量数据的最快方法

  • Z时代
  • 2024-01-10
  • 分类：问答

我必须在text [csv]文件中写入大量数据。我使用BufferedWriter写入数据，并且花费了大约40秒的时间来写入174 mb的数据。这是Java可以提供的最快速度吗？

bufferedWriter = new BufferedWriter ( new FileWriter ( "fileName.csv" ) );

注意：这40秒还包括从结果集中迭代和获取记录的时间。:) 174 mb用于结果集中的400000行。

回答：

你可以尝试删除BufferedWriter并直接使用FileWriter。在现代系统上，无论如何，你很有可能只是写入驱动器的缓存。

我需要4-5秒的时间来写入175MB（400万个字符串）-这是在运行Windows XP和80GB，7200-RPM日立磁盘的双核2.4GHz戴尔上进行的。

你能否确定记录检索有多少时间和文件写入有多少时间？

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");
}
}

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