Java实现下载文件的6种方式

1. 使用URL类的openStream()方法下载文件：
```java
URL url = new URL(fileUrl);
InputStream inputStream = url.openStream();
FileOutputStream outputStream = new FileOutputStream(savePath);
byte[] buffer = new byte[1024];
int bytesRead;
while ((bytesRead = inputStream.read(buffer)) != -1) {
outputStream.write(buffer, 0, bytesRead);
}
outputStream.close();
inputStream.close();
```
2. 使用URLConnection类下载文件：
```java
URL url = new URL(fileUrl);
HttpURLConnection httpConn = (HttpURLConnection) url.openConnection();
int responseCode = httpConn.getResponseCode();
if (responseCode == HttpURLConnection.HTTP_OK) {
InputStream inputStream = httpConn.getInputStream();
FileOutputStream outputStream = new FileOutputStream(savePath);
byte[] buffer = new byte[1024];
int bytesRead;
while ((bytesRead = inputStream.read(buffer)) != -1) {
outputStream.write(buffer, 0, bytesRead);
}
outputStream.close();
inputStream.close();
}
httpConn.disconnect();
```
3. 使用Apache HttpClient库下载文件：
```java
CloseableHttpClient httpClient = HttpClientBuilder.create().build();
HttpGet httpGet = new HttpGet(fileUrl);
CloseableHttpResponse response = httpClient.execute(httpGet);
HttpEntity entity = response.getEntity();
if (entity != null) {
InputStream inputStream = entity.getContent();
FileOutputStream outputStream = new FileOutputStream(savePath);
byte[] buffer = new byte[1024];
int bytesRead;
while ((bytesRead = inputStream.read(buffer)) != -1) {
outputStream.write(buffer, 0, bytesRead);
}
outputStream.close();
inputStream.close();
}
httpClient.close();
response.close();
```
4. 使用Java NIO下载文件：
```java
URL url = new URL(fileUrl);
ReadableByteChannel channel = Channels.newChannel(url.openStream());
FileOutputStream outputStream = new FileOutputStream(savePath);
outputStream.getChannel().transferFrom(channel, 0, Long.MAX_VALUE);
outputStream.close();
channel.close();
```
5. 使用Java IO和BufferedStream下载文件：
```java
URL url = new URL(fileUrl);
BufferedInputStream inputStream = new BufferedInputStream(url.openStream());
FileOutputStream outputStream = new FileOutputStream(savePath);
byte[] buffer = new byte[1024];
int bytesRead;
while ((bytesRead = inputStream.read(buffer)) != -1) {
outputStream.write(buffer, 0, bytesRead);
}
outputStream.close();
inputStream.close();
```
6. 使用Apache Commons IO库下载文件：
```java
URL url = new URL(fileUrl);
FileUtils.copyURLToFile(url, new File(savePath));
```
请注意，以上代码可能需要处理异常或添加进一步的逻辑来完善下载过程。