更简单的非阻塞I/O用法:

URL website = new URL("http://www.website.com/information.asp");
try (InputStream in = website.openStream()) {
    Files.copy(in, target, StandardCopyOption.REPLACE_EXISTING);
}

public class DownloadManager {

    static String urls = "[WEBSITE NAME]";

    public static void main(String[] args) throws IOException{
        URL url = verify(urls);
        HttpURLConnection connection = (HttpURLConnection) url.openConnection();
        InputStream in = null;
        String filename = url.getFile();
        filename = filename.substring(filename.lastIndexOf('/') + 1);
        FileOutputStream out = new FileOutputStream("C:\\Java2_programiranje/Network/DownloadTest1/Project/Output" + File.separator + filename);
        in = connection.getInputStream();
        int read = -1;
        byte[] buffer = new byte[4096];
        while((read = in.read(buffer)) != -1){
            out.write(buffer, 0, read);
            System.out.println("[SYSTEM/INFO]: Downloading file...");
        }
        in.close();
        out.close();
        System.out.println("[SYSTEM/INFO]: File Downloaded!");
    }
    private static URL verify(String url){
        if(!url.toLowerCase().startsWith("http://")) {
            return null;
        }
        URL verifyUrl = null;

        try{
            verifyUrl = new URL(url);
        }catch(Exception e){
            e.printStackTrace();
        }
        return verifyUrl;
    }
}

在java.net.http.HttpClient上使用授权的解决方案:

HttpClient client = HttpClient.newHttpClient();

HttpRequest request = HttpRequest.newBuilder()
        .GET()
        .header("Accept", "application/json")
        // .header("Authorization", "Basic ci5raG9kemhhZXY6NDdiYdfjlmNUM=") if you need
        .uri(URI.create("https://jira.google.ru/secure/attachment/234096/screenshot-1.png"))
        .build();

HttpResponse<InputStream> response = client.send(request, HttpResponse.BodyHandlers.ofInputStream());

try (InputStream in = response.body()) {
    Files.copy(in, Paths.get(target + "screenshot-1.png"), StandardCopyOption.REPLACE_EXISTING);
}

这个答案几乎和选中的答案完全一样，但是有两个增强:它是一个方法，它关闭了FileOutputStream对象:

    public static void downloadFileFromURL(String urlString, File destination) {
        try {
            URL website = new URL(urlString);
            ReadableByteChannel rbc;
            rbc = Channels.newChannel(website.openStream());
            FileOutputStream fos = new FileOutputStream(destination);
            fos.getChannel().transferFrom(rbc, 0, Long.MAX_VALUE);
            fos.close();
            rbc.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

你可以在一行中使用netloader for Java:

new NetFile(new File("my/zips/1.zip"), "https://example.com/example.zip", -1).load(); // Returns true if succeed, otherwise false.

如果你使用代理，你可以在Java程序中设置代理，如下所示:

Properties systemSettings = System.getProperties();
systemSettings.put("proxySet", "true");
systemSettings.put("https.proxyHost", "HTTPS proxy of your org");
systemSettings.put("https.proxyPort", "8080");

如果您没有使用代理，请不要在代码中包含上述代码行。完整的工作代码下载文件时，你是一个代理。

public static void main(String[] args) throws IOException {
    String url = "https://raw.githubusercontent.com/bpjoshi/fxservice/master/src/test/java/com/bpjoshi/fxservice/api/TradeControllerTest.java";
    OutputStream outStream = null;
    URLConnection connection = null;
    InputStream is = null;
    File targetFile = null;
    URL server = null;

    // Setting up proxies
    Properties systemSettings = System.getProperties();
        systemSettings.put("proxySet", "true");
        systemSettings.put("https.proxyHost", "HTTPS proxy of my organisation");
        systemSettings.put("https.proxyPort", "8080");
        // The same way we could also set proxy for HTTP
        System.setProperty("java.net.useSystemProxies", "true");
        // Code to fetch file
    try {
        server = new URL(url);
        connection = server.openConnection();
        is = connection.getInputStream();
        byte[] buffer = new byte[is.available()];
        is.read(buffer);

        targetFile = new File("src/main/resources/targetFile.java");
        outStream = new FileOutputStream(targetFile);
        outStream.write(buffer);
    } catch (MalformedURLException e) {
        System.out.println("THE URL IS NOT CORRECT ");
        e.printStackTrace();
    } catch (IOException e) {
        System.out.println("I/O exception");
        e.printStackTrace();
    }
    finally{
        if(outStream != null)
            outStream.close();
    }
}