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如何在官网下载Java的API文档?

题主你好,

首先导航到jdk下载的首页:

2.根据自己使用的jdk版本, 选择上图红框中相应的超链接, 点进去.

假设我使的是jdk15, 点进去后看到的页面为:

3.点击上图中红框中的Download the jdk(文档和jdk安装包都在这里面),看到页面为:

4.点击上图中红框选中的Documentation Download, 看到页面为:

5.点击上图红框中的超链接,会有弹窗:

6.按上图先将第1个红框勾选上, 然后点击Download jdk-16-doc-all.zip.

7.第6步做完就会自己下载了, 下载的是一个后缀为zip的安装包. 解压后, 导航到api目录, 里面有一个index.html,在浏览器里面访问这个index.html就可以用了.

*.如果题主有图形界面的话, 直接双击api步录下的index.html就可以.

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希望可以帮到题主, 欢迎追问.

如何用Java下载网上的文件?

这个涉及到文件的映射与跳转了,想要用JAVA写的话,最起码你传给它的应该是实质性的直接链接,这样它才可以建立连接,通过输入输出流。当然,如果你够厉害的话,也可以自己通过程序先对网址进行自动性的处理,然后分析出实质性的文件可靠地址,就可以下载了。

我看了一下,你的这个地址不是直接的链接,你发下载请求的时候人家直接在后台导向目标文件了。

用java实现文件的下载,如何提高下载速度(非web开发)

下面贴出的代码是一个简单的读取远程文件保存到本地的实现,至于提高下载速度你可以利用多线程,具体可参考最下面的那个网址——

import java.io.File;

import java.io.FileOutputStream;

import java.io.IOException;

import java.io.InputStream;

import java.net.URL;

public class DownloadTester {

public static void main(String[] args) throws IOException {

String urlStr = "";

String path = "D:/";

String name = urlStr.substring(urlStr.trim().lastIndexOf("/"));

URL url = new URL(urlStr);

InputStream in = url.openConnection().getInputStream();

File file = new File(path + name);

FileOutputStream out = new FileOutputStream(file, true);

int counter = 0;

int ch;

byte[] buffer = new byte[1024];

while ((ch = in.read(buffer)) != -1) {

out.write(buffer, 0, ch);

counter += ch;

System.out.println(counter + ":byte");

}

out.flush();

in.close();

out.close();

}

}

Java 下载文件的方法怎么写

参考下面

public HttpServletResponse download(String path, HttpServletResponse response) {

try {

// path是指欲下载的文件的路径。

File file = new File(path);

// 取得文件名。

String filename = file.getName();

// 取得文件的后缀名。

String ext = filename.substring(filename.lastIndexOf(".") + 1).toUpperCase();

// 以流的形式下载文件。

InputStream fis = new BufferedInputStream(new FileInputStream(path));

byte[] buffer = new byte[fis.available()];

fis.read(buffer);

fis.close();

// 清空response

response.reset();

// 设置response的Header

response.addHeader("Content-Disposition", "attachment;filename=" + new String(filename.getBytes()));

response.addHeader("Content-Length", "" + file.length());

OutputStream toClient = new BufferedOutputStream(response.getOutputStream());

response.setContentType("application/octet-stream");

toClient.write(buffer);

toClient.flush();

toClient.close();

} catch (IOException ex) {

ex.printStackTrace();

}

return response;

}

// 下载本地文件

public void downloadLocal(HttpServletResponse response) throws FileNotFoundException {

String fileName = "Operator.doc".toString(); // 文件的默认保存名

// 读到流中

InputStream inStream = new FileInputStream("c:/Operator.doc");// 文件的存放路径

// 设置输出的格式

response.reset();

response.setContentType("bin");

response.addHeader("Content-Disposition", "attachment; filename=\"" + fileName + "\"");

// 循环取出流中的数据

byte[] b = new byte[100];

int len;

try {

while ((len = inStream.read(b)) 0)

response.getOutputStream().write(b, 0, len);

inStream.close();

} catch (IOException e) {

e.printStackTrace();

}

}

// 下载网络文件

public void downloadNet(HttpServletResponse response) throws MalformedURLException {

int bytesum = 0;

int byteread = 0;

URL url = new URL("windine.blogdriver.com/logo.gif");

try {

URLConnection conn = url.openConnection();

InputStream inStream = conn.getInputStream();

FileOutputStream fs = new FileOutputStream("c:/abc.gif");

byte[] buffer = new byte[1204];

int length;

while ((byteread = inStream.read(buffer)) != -1) {

bytesum += byteread;

System.out.println(bytesum);

fs.write(buffer, 0, byteread);

}

} catch (FileNotFoundException e) {

e.printStackTrace();

} catch (IOException e) {

e.printStackTrace();

}

}

//支持在线打开文件的一种方式

public void downLoad(String filePath, HttpServletResponse response, boolean isOnLine) throws Exception {

File f = new File(filePath);

if (!f.exists()) {

response.sendError(404, "File not found!");

return;

}

BufferedInputStream br = new BufferedInputStream(new FileInputStream(f));

byte[] buf = new byte[1024];

int len = 0;

response.reset(); // 非常重要

if (isOnLine) { // 在线打开方式

URL u = new URL("" + filePath);

response.setContentType(u.openConnection().getContentType());

response.setHeader("Content-Disposition", "inline; filename=" + f.getName());

// 文件名应该编码成UTF-8

} else { // 纯下载方式

response.setContentType("application/x-msdownload");

response.setHeader("Content-Disposition", "attachment; filename=" + f.getName());

}

OutputStream out = response.getOutputStream();

while ((len = br.read(buf)) 0)

out.write(buf, 0, len);

br.close();

out.close();

}

Java文件下载怎么实现的

下载就很简单了

把你要下载的文件做成超级链接,可以不用任何组件

比如说

下载一个word文档

a href="名称.doc"名称.doc/a

路径你自己写

import java.io.File;

import java.io.FileNotFoundException;

import java.io.IOException;

import java.io.InputStream;

import java.io.RandomAccessFile;

import java.net.HttpURLConnection;

import java.net.ProtocolException;

import java.net.URI;

import java.net.URL;

import java.util.Random;

/**

*

* 实现了下载的功能*/

public class SimpleTh {

public static void main(String[] args){

// TODO Auto-generated method stub

//String path = "倩女幽魂.mp3";//MP3下载的地址

String path ="";

try {

new SimpleTh().download(path, 3); //对象调用下载的方法

} catch (Exception e) {

// TODO Auto-generated catch block

e.printStackTrace();

}

}

public static String getFilename(String path){//获得文件的名字

return path.substring(path.lastIndexOf('/')+1);

}

public void download(String path,int threadsize) throws Exception//下载的方法

{//参数 下载地址,线程数量

URL url = new URL(path);

HttpURLConnection conn = (HttpURLConnection)url.openConnection();//获取HttpURLConnection对象

conn.setRequestMethod("GET");//设置请求格式,这里是GET格式

conn.setReadTimeout(5*1000);//

int filelength = conn.getContentLength();//获取要下载文件的长度

String filename = getFilename(path);

File saveFile = new File(filename);

RandomAccessFile accessFile = new RandomAccessFile(saveFile, "rwd");

accessFile.setLength(filelength);

accessFile.close();

int block = filelength%threadsize ==0?filelength/threadsize:filelength/threadsize+1;

for(int threadid = 0;threadid=threadsize;threadid++){

new DownloadThread(url,saveFile,block,threadid).start();

}

}

private final class DownloadThread extends Thread{

private URL url;

private File saveFile;

private int block;//每条线程下载的长度

private int threadid;//线程id

public DownloadThread(URL url,File saveFile,int block,int threadid){

this.url = url;

this.saveFile= saveFile;

this.block = block;

this.threadid = threadid;

}

@Override

public void run() {

//计算开始位置的公式:线程id*每条线程下载的数据长度=?

//计算结束位置的公式:(线程id+1)*每条线程下载数据长度-1=?

int startposition = threadid*block;

int endposition = (threadid+1)*block-1;

try {

try {

RandomAccessFile accessFile = new RandomAccessFile(saveFile, "rwd");

accessFile.seek(startposition);//设置从什么位置写入数据

HttpURLConnection conn = (HttpURLConnection)url.openConnection();

conn.setRequestMethod("GET");

conn.setReadTimeout(5*1000);

conn.setRequestProperty("Range","bytes= "+startposition+"-"+endposition);

InputStream inStream = conn.getInputStream();

byte[]buffer = new byte[1024];

int len = 0;

while((len = inStream.read(buffer))!=-1){

accessFile.write(buffer, 0, len);

}

inStream.close();

accessFile.close();

System.out.println("线程id:"+threadid+"下载完成");

} catch (FileNotFoundException e) {

e.printStackTrace();

}

} catch (IOException e) {

e.printStackTrace();

}

}

}

}