Java如何实现下载文件的几种方式

java下载文件的方式

Java 提供了多种下载文件的方法。以下是几种常用的方式：

1. 使用 URL.openStream()

<code class="java">URL url = new URL("https://example.com/file.txt");
URLConnection connection = url.openConnection();
InputStream inputStream = connection.getInputStream();
FileOutputStream fileOutputStream = new FileOutputStream("file.txt");
byte[] buffer = new byte[1024];
int len;
while ((len = inputStream.read(buffer)) > 0) {
    fileOutputStream.write(buffer, 0, len);
}</code>

2. 使用 HttpClient

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<code class="java">HttpClient client = HttpClientBuilder.create().build();
HttpGet request = new HttpGet("https://example.com/file.txt");
HttpResponse response = client.execute(request);
HttpEntity entity = response.getEntity();
InputStream inputStream = entity.getContent();
FileOutputStream fileOutputStream = new FileOutputStream("file.txt");
byte[] buffer = new byte[1024];
int len;
while ((len = inputStream.read(buffer)) > 0) {
    fileOutputStream.write(buffer, 0, len);
}</code>

3. 使用 URLConnection

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<code class="java">URL url = new URL("https://example.com/file.txt");
URLConnection connection = url.openConnection();
connection.setDoInput(true);
connection.connect();
InputStream inputStream = connection.getInputStream();
FileOutputStream fileOutputStream = new FileOutputStream("file.txt");
byte[] buffer = new byte[1024];
int len;
while ((len = inputStream.read(buffer)) > 0) {
    fileOutputStream.write(buffer, 0, len);
}</code>

4. 使用 Java NIO

<code class="java">Path path = Paths.get("file.txt");
FileChannel fileChannel = FileChannel.open(path, StandardOpenOption.WRITE);
SocketChannel socketChannel = SocketChannel.open();
socketChannel.connect(new InetSocketAddress("example.com", 80));
ByteBuffer buffer = ByteBuffer.allocate(1024);
while ((len = socketChannel.read(buffer)) > 0) {
    fileChannel.write(buffer, 0, len);
}</code>