java怎么下载文件?常见的java下载文件的方法介绍!

在Java中，可以通过多种方式来下载文件。以下是常见的几种方法介绍：

1. 使用Java标准库中的URL和URLConnection类：

```java

import java.io.BufferedInputStream;

import java.io.FileOutputStream;

import java.io.IOException;

import java.io.InputStream;

import java.net.URL;

import java.net.URLConnection;

public class FileDownloader {

public static void downloadFile(String fileUrl

String saveTo) {

try {

URL url = new URL(fileUrl);

URLConnection connection = url.openConnection();

InputStream in = new BufferedInputStream(connection.getInputStream());

FileOutputStream out = new FileOutputStream(saveTo);

int byteRead;

while ((byteRead = in.read()) != -1) {

out.write(byteRead);

}

in.close();

out.close();

} catch (IOException e) {

e.printStackTrace();

}

}

public static void main(String[] args) {

String fileUrl = "http://example.com/file.txt";

String saveTo = "file.txt";

downloadFile(fileUrl

saveTo);

}

}

```

2. 使用Apache HttpComponents库：

```java

import org.apache.http.client.methods.HttpGet;

import org.apache.http.impl.client.CloseableHttpClient;

import org.apache.http.impl.client.HttpClients;

import org.apache.http.util.EntityUtils;

import java.io.FileOutputStream;

import java.io.IOException;

public class FileDownloader {

public static void downloadFile(String fileUrl

String saveTo) {

CloseableHttpClient httpClient = HttpClients.createDefault();

HttpGet httpGet = new HttpGet(fileUrl);

try {

byte[] fileBytes = httpClient.execute(httpGet

response -> EntityUtils.toByteArray(response.getEntity()));

FileOutputStream out = new FileOutputStream(saveTo);

out.write(fileBytes);

out.close();

} catch (IOException e) {

e.printStackTrace();

} finally {

try {

httpClient.close();

} catch (IOException e) {

e.printStackTrace();

}

}

}

public static void main(String[] args) {

String fileUrl = "http://example.com/file.txt";

String saveTo = "file.txt";

downloadFile(fileUrl

saveTo);

}

}

```

3. 使用Java NIO（New Input/Output）：

```java

import java.io.FileOutputStream;

import java.io.IOException;

import java.io.InputStream;

import java.net.URL;

import java.nio.channels.Channels;

import java.nio.channels.ReadableByteChannel;

public class FileDownloader {

public static void downloadFile(String fileUrl

String saveTo) {

try {

URL url = new URL(fileUrl);

try (InputStream in = url.openStream();

ReadableByteChannel rbc = Channels.newChannel(in);

FileOutputStream out = new FileOutputStream(saveTo)) {

out.getChannel().transferFrom(rbc

0

Long.MAX_VALUE);

}

} catch (IOException e) {

e.printStackTrace();

}

}

public static void main(String[] args) {

String fileUrl = "http://example.com/file.txt";

String saveTo = "file.txt";

downloadFile(fileUrl

saveTo);

}

}

```

以上是几种常见的Java下载文件的方法介绍，开发者可以根据自己的需求选择合适的方法来实现文件下载功能。