Question

我正在尝试打印URL的内容，但第一个字符在许多行中丢失。如下面的输出“＆lt;”在DOCTYPE，head和html标签中缺少。

我尝试在while循环中使用readLine方法但是它显示了一个更奇怪的输出，其中DOCTYPE，头标记丢失，最后为null。

代码1：

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.net.URL;
import java.net.URLConnection;

public class urlConnect {
public static void main(String[] args) throws Exception {
     URL urlObj = new URL("https://soundcloud.com");
     URLConnection conn = urlObj.openConnection();
     BufferedReader br = new BufferedReader(new InputStreamReader(conn.getInputStream()));
     while ((br.read()) != -1) {
     System.out.println((br.readLine()));
     }
 }
}

输出1：

!DOCTYPE html>
<html lang="en">
head>
 <meta charset="utf-8">
 
 <meta http-equiv="X-UA-Compatible" content="IE=edge,chrome=1">
  
...
...
...
</body>
/html>

代码2：

while ((br.readLine()) != null) {
System.out.println((br.readLine()));
 }

输出2：

<head>
  

  <link rel="dns-prefetch" href="//style.sndcdn.com">
  <link rel="dns-prefetch" href="//api-v2.soundcloud.com">
  <link rel="dns-prefetch" href="//secure.quantserve.com">
  <link rel="dns-prefetch" href="//api.soundcloud.com">
  <link rel="dns-prefetch" href="//i1.sndcdn.com">
  <link rel="dns-prefetch" href="//i3.sndcdn.com">
  <link rel="dns-prefetch" href="//wis.sndcdn.com">
  <link rel="dns-prefetch" href="//pixel.quantserve.com">
  ...
  ...
  ...
     <script type="text/javascript">window.__sc_version = "1495803442";
    
  
    
</body>
null

Answer 1

Here's BufferedReader.read()的javadoc，这就是它所说的：

读取单个字符。

<强>返回：   字符读取为0到65535（0x00-0xffff）范围内的整数，如果已到达流末尾则为-1

现在，我们来看看代码：

while ((br.read()) != -1) {
   System.out.println((br.readLine()));
}

您正在检查返回值read以查看是否已到达流的末尾。但是，您不打印该值（它不会存储在任何引用中，因此在比较后会丢失）。理想情况下，您需要将该值与整行一起打印，例如：

String line;
while((line = br.readLine()) != null){
    System.out.println(line);
}

Answer 2

这是完整的工作代码。我提到了Oracle Java文档https://docs.oracle.com/javase/tutorial/networking/urls/readingURL.html

import java.util.*;
import java.lang.*;
import java.io.*;
import java.net.URL;
import java.net.URLConnection;


public class TestURL
{
        public static void main (String[] args) throws java.lang.Exception
        {
        URL oracle = new URL("https://soundcloud.com/");
        BufferedReader in = new BufferedReader(
        new InputStreamReader(oracle.openStream()));

        String inputLine;
        while ((inputLine = in.readLine()) != null)
            System.out.println(inputLine);
        in.close();
        }
}

来自BufferedReader

2 个答案: