今天机试的三个小题目
1、递归遍历磁盘文件路径
使用递归方法，遍历D盘(也可以更换成别的目录，效果达到即可)下全部的文件（包括子文件夹下的文件），输出文件路径，文件修改时间，文件按修改时间倒序排列。
package test;
import java.io.File;
import java.util.*;
/**
* Created by shimengru on 2020/3/2.
* 使用递归遍历apache目录下所有文件的文件名
*/
public class ShowFileDir {
public static void main(String[] args) {
File file = new File("/Users/admin/Downloads/apache-maven-3.6.2/");
//校验路径是否为空
File[] files = file.listFiles();
if (files == null) {
System.out.println("请输入正确路径...");
return;
}
File[] fs = seachFileDir(file);//查询后未排序
//进行排序
Arrays.sort(fs, new CompareByLastModified());
//遍历
for (File f : fs) {
System.out.println("文件名：" + f.getName());
System.out.println("文件路径：" + f.getAbsolutePath());
System.out.println("文件更新时间：" + new Date(f.lastModified()));
}
}
/**
* 根据更新时间倒序
*/
static class CompareByLastModified implements Comparator<File> {
public int compare(File f1, File f2) {
long diff = f1.lastModified() - f2.lastModified();
if (diff > 0)
return -1;
else if (diff == 0)
return 0;
else
return 1;
}
}
/**
* 递归查询文件
*/
public static File[] seachFileDir(File file) {
// 创建一个空的list
List<File> fileList = new ArrayList<>();
File[] files = file.listFiles();
//遍历根目录
for (File f : files) {
if (f.isFile()) {
// 如果是文件则直接添加到list
fileList.add(f);
} else if (f.isDirectory()) {
// 递归调用
seachFileDir(f);
}
}
return files;
}
}
2、模拟抽奖
tring s1 = “1,2,3,4,5,6,7,8.9,10,11,12,13,14,15”;//代表全部参与抽奖的人员编号
String s2 =”2,5,6”;//代表已经中奖的人员编号
int number = 3;
写一个函数，从s1中随机筛选出number个数字，且此数字不在s2中。返回一个字符串。
请理解好需求，假设s1是全公司人员编号，s2是一等奖中奖人员，现在是要抽取n个二等奖。
package test;
import java.util.Random;
/**
* Created by shimengru on 2020/3/2.
*/
public class LotteryDraw {
public static void main(String[] args) {
String s1 = "1,2,3,4,5,6,7,8.9,10,11,12,13,14,15";//代表全部参与抽奖的人员编号
String s2 ="2,5,6";//代表已经中奖的人员编号
int number = 3;
String[] s1Array = s1.split(",");
String[] s2Array = s2.split(",");
Random r = new Random();
for (int i = 0; i < number; ) {
int i1 = r.nextInt(s1Array.length)-1;
if(!arrayContains(s2Array,s1Array[i1])){
i++;
System.out.println(s1Array[i1]);
}
}
}
/**
* 查询是否包含
*/
private static boolean arrayContains(String[] chars,String c){
for (int i = 0; i < chars.length; i++) {
if(c.equals(chars[i])) return true;
}
return false;
}
}
3、线上解析json并下载图片
读取并解析json文件: http://123.56.191.196:8080/a/a/d/list_slide_1_0.json，必须是在线读取。把里面的图片下载到本地，并打印出图片文件名和文件大小。
package test;
import com.alibaba.fastjson.JSON;
import com.alibaba.fastjson.JSONArray;
import com.alibaba.fastjson.JSONObject;
import okhttp3.ConnectionPool;
import okhttp3.OkHttpClient;
import okhttp3.Request;
import okhttp3.Response;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.util.concurrent.TimeUnit;
/**
* Created by shimengru on 2020/3/2.
*/
public class ParseJson {
private static final OkHttpClient client = new OkHttpClient.Builder()
.connectTimeout(10, TimeUnit.SECONDS)
.writeTimeout(15, TimeUnit.SECONDS)
.readTimeout(15, TimeUnit.SECONDS)
.connectionPool(new ConnectionPool(10, 60, TimeUnit.SECONDS))
.retryOnConnectionFailure(true)
.build();
public static void main(String[] args) {
Request request = new Request.Builder()
.url("http://123.56.191.196:8080/a/a/d/list_slide_1_0.json")
.get()
.build();
//请求URL下载内容
try (Response response = client.newCall(request).execute()) {
if (!response.isSuccessful()) throw new IOException("Unexpected code " + response);
String responseText = response.body().string();
//转为json数组
JSONArray objects = JSON.parseArray(responseText);
for (int i = 0; i < objects.size(); i++) {
JSONObject jsonObject = objects.getJSONObject(i);
String photoUrl = jsonObject.getString("photo");
String title = jsonObject.getString("title");
//下载图片
downloadPicture(photoUrl, title);
}
} catch (IOException e) {
e.printStackTrace();
}
}
private static void downloadPicture(String url, String title) {
Request request = new Request.Builder()
.url(url)
.get()
.build();
try (Response response = client.newCall(request).execute()) {
if (!response.isSuccessful()) throw new IOException("Unexpected code " + response);
InputStream inputStream = response.body().byteStream();
String fileName = "D:\\data\\" + title + ".jpg";
FileOutputStream outputStream = new FileOutputStream(fileName);
byte[] data = new byte[1024];
int i, fileSize = 0;
while ((i = inputStream.read(data, 0, data.length)) > 0) {
outputStream.write(data, 0, i);
fileSize += i;
}
System.out.println("文件名："+fileName);
System.out.println("文件大小："+fileSize +"B");
} catch (IOException e) {
e.printStackTrace();
}
}
}
pom文件
<dependency>
<groupId>com.squareup.okhttp3</groupId>
<artifactId>okhttp-apache</artifactId>
<version>3.8.1</version>
</dependency>
<dependency>
<groupId>org.apache.httpcomponents</groupId>
<artifactId>httpclient</artifactId>
<version>4.5.6</version>
</dependency>
<dependency>
<groupId>com.alibaba</groupId>
<artifactId>fastjson</artifactId>
<version>1.2.56</version>
</dependency>
来源：oschina
链接：https://my.oschina.net/AnniHome/blog/3185402