Java SE單線程下載網絡上的音/視頻等大文件

import static org.junit.Assert.fail;

import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.FileOutputStream;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.URL;

import org.junit.Test;


public class InternetTest {

    @Test
    public void test() {
        fail("Not yet implemented");
    }
    @Test
    public void getImage() throws Exception{
        //首先要獲取請求的路徑，路徑就是要從網上獲取的資源
        String urlPath= "http://c.hiphotos.baidu.com/image/pic/item/8718367adab44aedbc2df1e3b01c8701a18bfb52.jpg";
        URL url = new URL(urlPath);//建立URL類對象，拋出異常
        HttpURLConnection conn =(HttpURLConnection)url.openConnection();//得到UrlConnection對象

        conn.setRequestMethod("GET");//聲明請求方式
        conn.setConnectTimeout(6*1000);//設置連接超時
        if(conn.getResponseCode() == 200){//如果結果是200，就代表他的請求是成功的
            InputStream inputStream = conn.getInputStream();//得到服務器端傳回來的數據，相對客戶端爲輸入流

            byte[] data = readInstream(inputStream);
            File file = new File("touxiang.jpg");
            FileOutputStream outputStream = new FileOutputStream(file);
            outputStream.write(data);
            outputStream.close();       
        }       
    }

    private byte[] readInstream(InputStream inputStream) throws Exception{
        ByteArrayOutputStream byteArrayOutPutStream = new ByteArrayOutputStream();//創建ByteArrayOutputStream類
        byte[] buffer = new byte[1024];//聲明緩存區
        int length = -1;//定義讀取的默認長度
        while((length = inputStream.read(buffer))!= -1){
            byteArrayOutPutStream.write(buffer,0,length);//把緩存區中的輸入到內存中         
        };
        byteArrayOutPutStream.close();//關閉輸入流
        inputStream.close();//關閉輸入流

        return byteArrayOutPutStream.toByteArray();//返回這個輸入流的字節數組
    }

}

J2SE從網絡中獲取文本

    @Test
    public void getHtml() throws Exception{
        String urlpathString = "http://www.sina.com";
        URL url = new URL(urlpathString);//建立URL對象，拋出異常
        HttpURLConnection conn = (HttpURLConnection)url.openConnection();
        conn.setRequestMethod("GET");
        conn.setConnectTimeout(6*1000);
        if(conn.getResponseCode() == 200){
            InputStream inputStream = conn.getInputStream();//得到輸入流
            byte[] data = readInstream(inputStream);     //得到數據
            System.out.println(new String(data));//將字節轉化爲字符串，打印在控制檯上面
        }
    }

System.out.println(new String(data)); 是將得到的字符串類型打印到控制檯上面，返回是ＨＴＭＬ的代碼，和流量器參看的源代碼是一樣的。

第三種：J2SE從網絡獲取可以自行的文件。
在Internet類中添加getFile()方法，具體代碼如下：

@Test
    public void getFile() throws Exception{
        String urlPath  = "http://dlsw.baidu.com/sw-search-sp/soft/b8/14630/YoudaoDict_V6.3.66.1117_setup.1423550350.exe";
        URL url = new URL(urlPath);
        HttpURLConnection connection = (HttpURLConnection) url.openConnection();
        connection.setRequestMethod("GET");
        connection.setConnectTimeout(6*1000);
        if(connection.getResponseCode()== 200){
            InputStream inputStream =connection.getInputStream();
            byte[] data =readInstream(inputStream);
            File file =new File("youdao.exe");
            FileOutputStream outputStream = new FileOutputStream(file);
            outputStream.write(data);
            outputStream.close();
        }
    }