java随机产生指定大小文件

文章目录

• 原因
• 代码:

原因

今天在做测试的时候,需要一个5M的文件,然后一开始是直接ctrl C+ctrl V,虽说也很快,但是很傻,虽然你自信的ctrl C的时候真的很帅,但是后面需求变更的时候,你真的很傻.然后我就简单的写了一个工具类,生成指定大小的文件,就是随机数字for遍历然后加起来…测试嘛,随便搞一下,不会很慢.

代码:

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStreamWriter;
import java.util.Random;
import java.util.concurrent.CompletableFuture;
import java.util.concurrent.CountDownLatch;

/**
 * @Version 2020-05-07 14:53
 * @Version 1.0
 * @Description FileCreatUtil单纯的测试使用,单位是M
 */
public class FileCreatUtil {

  //随机产生指定大小的文件,纯数字
  public static void createNewFile(String path, int sizeM) throws Exception {
    File file = new File(path);
    int size = sizeM;
    if (!file.exists()) {
      file.createNewFile();
    }
    FileOutputStream fos = new FileOutputStream(file);
    OutputStreamWriter osw = new OutputStreamWriter(fos, "utf-8");
    CountDownLatch countDownLatch = new CountDownLatch(size);
    for (int i = 0; i < size; i++) {
      CompletableFuture<StringBuilder> c = oneM();
      c.whenComplete((x, y) -> {
        if (x != null) {
          try {
            osw.append(x);
            osw.flush();
          } catch (IOException e) {
            e.printStackTrace();
          }
        }
        countDownLatch.countDown();
      });
    }
    countDownLatch.await();
    osw.close();
  }

  //随机产生指定大小的String
  public static String createString(int sizeM) throws Exception {
    int size = sizeM;
    StringBuffer stringBuffer = new StringBuffer();
    CountDownLatch countDownLatch = new CountDownLatch(size);
    for (int i = 0; i < size; i++) {
      CompletableFuture<StringBuilder> c = oneM();
      c.whenComplete((x, y) -> {
        if (x != null) {
          stringBuffer.append(x);
        }
        countDownLatch.countDown();
      });
    }
    countDownLatch.await();
    return stringBuffer.toString();
  }

  private static CompletableFuture<StringBuilder> oneM() {
    Random r = new Random();
    CompletableFuture<StringBuilder> c = CompletableFuture.supplyAsync(() -> {
      StringBuilder sb = new StringBuilder();
      for (int i = 0; i < 1024 * 1024; i++) {
        sb.append(r.nextInt(10));
      }
      return sb;
    });
    return c;
  }

  public static void main(String[] args) throws Exception {
    //几M
    String string = createString(3);
    System.out.println(1);
//    createNewFile("E:\2.txt", 3);
  }


}

一身轻松!..
建议1G以内,太大,会卡死,因为直接使用的for循环…