Это должно сработать:
import java.io.*;
import java.net.*;
...
try {
URL fileUrl = new URL("someurl);
BufferedInputStream in = new BufferedInputStream(fileUrl.openStream());
FileOutputStream fos = new FileOutputStream("/home/user/download/file");
BufferedOutputStream bout = new BufferedOutputStream(fos, BUFFER_SIZE);
byte[] data = new byte[1024];
int x;
while ((x = in.read(data, 0, 1024)) >= 0) {
bout.write(data, 0, x);
}
bout.close();
in.close();
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException ex) {
ex.printStackTrace();
}