从 BufferedReader 中缺少多行中的第一个字符

Question

我正在尝试打印 URL 的内容，但第一个字符在很多行中都丢失了。就像在下面的输出中一样，DOCTYPE、head 和 html 标签中缺少“<”。

我试过在 while 循环中使用 readLine 方法，但它显示了一个更奇怪的 DOCTYPE 输出，缺少头标签，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，是这样写的：

Reads a single character.

Returns: The character read, as an integer in the range 0 to 65535 (0x00-0xffff), or -1 if the end of the stream has been reached

现在，让我们看一下代码：

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

您正在检查 return 值 read 以查看是否已到达流的末尾。但是，您并未打印该值（它未存储在任何引用中，因此在比较后会丢失）。理想情况下，您需要打印该值以及整行，例如：

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

Answer 2

这是完整的工作代码。我参考了 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();
        }
}

从 BufferedReader 中缺少多行中的第一个字符

Missing first character in many lines while from BufferedReader

java

bufferedreader