废话不多说了，直接给大家贴代码了，具体代码如下所示；
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package com.github.pandafang.tool;
import java.io.BufferedOutputStream;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.URL;
import java.nio.channels.Channels;
import java.nio.channels.FileChannel;
import java.nio.channels.ReadableByteChannel;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.nio.file.StandardCopyOption;
import org.apache.commons.io.FileUtils;
/**
* 文件工具类
* @author panda fang
* @date 2017-08-26
* @version 1.0
*/
public class FileTool {
/**
* 使用传统io stream 下载文件
* @param url
* @param saveDir
* @param fileName
*/
public static void download(String url, String saveDir, String fileName) {
BufferedOutputStream bos = null;
InputStream is = null;
try {
byte[] buff = new byte[8192];
is = new URL(url).openStream();
File file = new File(saveDir, fileName);
file.getParentFile().mkdirs();
bos = new BufferedOutputStream(new FileOutputStream(file));
int count = 0;
while ( (count = is.read(buff)) != -1) {
bos.write(buff, 0, count);
}
}
catch (IOException e) {
e.printStackTrace();
}
finally {
if (is != null) {
try {
is.close();
} catch (IOException e) {
e.printStackTrace();
}
}
if (bos != null) {
try {
bos.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
/**
* 利用 commonio 库下载文件，依赖Apache Common IO ，官网 https://commons.apache.org/proper/commons-io/
* @param url
* @param saveDir
* @param fileName
*/
public static void downloadByApacheCommonIO(String url, String saveDir, String fileName) {
try {
FileUtils.copyURLToFile(new URL(url), new File(saveDir, fileName));
} catch (IOException e) {
e.printStackTrace();
}
}
/**
* 使用NIO下载文件， 需要 jdk 1.4+
* @param url
* @param saveDir
* @param fileName
*/
public static void downloadByNIO(String url, String saveDir, String fileName) {
ReadableByteChannel rbc = null;
FileOutputStream fos = null;
FileChannel foutc = null;
try {
rbc = Channels.newChannel(new URL(url).openStream());
File file = new File(saveDir, fileName);
file.getParentFile().mkdirs();
fos = new FileOutputStream(file);
foutc = fos.getChannel();
foutc.transferFrom(rbc, 0, Long.MAX_VALUE);
} catch (IOException e) {
e.printStackTrace();
} finally {
if (rbc != null) {
try {
rbc.close();
} catch (IOException e) {
e.printStackTrace();
}
}
if (foutc != null) {
try {
foutc.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
/**
* 使用NIO下载文件， 需要 jdk 1.7+
* @param url
* @param saveDir
* @param fileName
*/
public static void downloadByNIO2(String url, String saveDir, String fileName) {
try (InputStream ins = new URL(url).openStream()) {
Path target = Paths.get(saveDir, fileName);
Files.createDirectories(target.getParent());
Files.copy(ins, target, StandardCopyOption.REPLACE_EXISTING);
} catch (IOException e) {
e.printStackTrace();
}
}
}
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下载一个百度logo 测试一下
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public static void main(String[] args) {
FileTool.downloadByNIO2("http://www.baidu.com/img/bd_logo1.png", "/home/panda/picture", "baidu_logo.png");
System.out.println("done...");
}
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总结
以上所述是小编给大家介绍的Java 从网上下载文件的几种方式实例代码详解，希望对大家有所帮助，如果大家有任何疑问请给我留言，小编会及时回复大家的。在此也非常感谢大家对服务器之家网站的支持！