这可以读取互联网上的文件，并将其写入文件。

import java.net.URL;
import java.io.FileOutputStream;
import java.io.File;

public class Download {
    public static void main(String[] args) throws Exception {
         URL url = new URL("https://www.google.com/images/branding/googlelogo/1x/googlelogo_color_272x92dp.png");  // Input URL
         FileOutputStream out = new FileOutputStream(new File("out.png"));  // Output file
         out.write(url.openStream().readAllBytes());
         out.close();
    }
}

使用Apache Commons IO。它只是一行代码:

FileUtils.copyURLToFile(URL, File)

在underscore-java库中有一个方法U.fetch(url)。

文件pom.xml:

<dependency>
  <groupId>com.github.javadev</groupId>
  <artifactId>underscore</artifactId>
  <version>1.84</version>
</dependency>

代码示例:

import com.github.underscore.U;
import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Paths;

public class Download {
    public static void main(String[] args) throws IOException {
        Files.write(Paths.get("data.bin"),
            U.fetch("https://stackoverflow.com/questions"
                + "/921262/how-to-download-and-save-a-file-from-internet-using-java").blob());
    }
}

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);
}

这是另一个基于Brian Risk的答案的Java 7变体，使用了try-with语句:

public static void downloadFileFromURL(String urlString, File destination) throws Throwable {

    URL website = new URL(urlString);
    try(
        ReadableByteChannel rbc = Channels.newChannel(website.openStream());
        FileOutputStream fos = new FileOutputStream(destination);
       ) {

        fos.getChannel().transferFrom(rbc, 0, Long.MAX_VALUE);
    }
}

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();
        }
    }