做商城网站企业/长沙做网站的公司有哪些

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Stringpublic 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MString 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…

使用common包

org.apache.commons.lang包下有一个RandomStringUtils类，其中有一个randomAlphanumeric(int length)函数，可以随机生成一个长度为length的字符串。

String filename=RandomStringUtils.randomAlphanumeric(1024*1024);