里面一个语句看不懂啊(String patternString = "<a\\s+href\\s*=\\s*(\"[^\"]*\"|[^\\s>])\\s*>";)里面的\\s是个什么东西啊
例子是Corejava里12章的一个例子HrefMatch.javaimport java.io.*;
import java.net.*;
import java.util.regex.*;/**
This program displays all URLs in a web page by
matching a regular expression that describes the
<a href=...> HTML tag. Start the program as
java HrefMatch URL
*/
public class HrefMatch
{
public static void main(String[] args)
{
try
{
// get URL string from command line or use default
String urlString;
if (args.length > 0) urlString = args[0];
else urlString = "http://java.sun.com"; // open reader for URL
InputStreamReader in = new InputStreamReader(new URL(urlString).openStream()); // read contents into string buffer
StringBuilder input = new StringBuilder();
int ch;
while ((ch = in.read()) != -1) input.append((char) ch); // search for all occurrences of pattern
String patternString = "<a\\s+href\\s*=\\s*(\"[^\"]*\"|[^\\s>])\\s*>"; Pattern pattern = Pattern.compile(patternString, Pattern.CASE_INSENSITIVE);
Matcher matcher = pattern.matcher(input); while (matcher.find())
{
int start = matcher.start();
int end = matcher.end();
String match = input.substring(start, end);
System.out.println(match);
}
}
catch (IOException e)
{
e.printStackTrace();
}
catch (PatternSyntaxException e)
{
e.printStackTrace();
}
}
}
例子是Corejava里12章的一个例子HrefMatch.javaimport java.io.*;
import java.net.*;
import java.util.regex.*;/**
This program displays all URLs in a web page by
matching a regular expression that describes the
<a href=...> HTML tag. Start the program as
java HrefMatch URL
*/
public class HrefMatch
{
public static void main(String[] args)
{
try
{
// get URL string from command line or use default
String urlString;
if (args.length > 0) urlString = args[0];
else urlString = "http://java.sun.com"; // open reader for URL
InputStreamReader in = new InputStreamReader(new URL(urlString).openStream()); // read contents into string buffer
StringBuilder input = new StringBuilder();
int ch;
while ((ch = in.read()) != -1) input.append((char) ch); // search for all occurrences of pattern
String patternString = "<a\\s+href\\s*=\\s*(\"[^\"]*\"|[^\\s>])\\s*>"; Pattern pattern = Pattern.compile(patternString, Pattern.CASE_INSENSITIVE);
Matcher matcher = pattern.matcher(input); while (matcher.find())
{
int start = matcher.start();
int end = matcher.end();
String match = input.substring(start, end);
System.out.println(match);
}
}
catch (IOException e)
{
e.printStackTrace();
}
catch (PatternSyntaxException e)
{
e.printStackTrace();
}
}
}
反斜线字符 ('\') 用于引用转义构造,如上表所定义的,同时还用于引用其他将被解释为非转义构造的字符。因此,表达式 \\ 与单个反斜线匹配,而 \{ 与左括号匹配。 在不表示转义构造的任何字母字符前使用反斜线都是错误的;它们是为将来扩展正则表达式语言保留的。可以在非字母字符前使用反斜线,不管该字符是否非转义构造的一部分。 根据 Java Language Specification 的要求,Java 源代码的字符串中的反斜线被解释为 Unicode 转义或其他字符转义。因此必须在字符串字面值中使用两个反斜线,表示正则表达式受到保护,不被 Java 字节码编译器解释。例如,当解释为正则表达式时,字符串字面值 "\b" 与单个退格字符匹配,而 "\\b" 与单词边界匹配。字符串字面值 "\(hello\)" 是非法的,将导致编译时错误;要与字符串 (hello) 匹配,必须使用字符串字面值 "\\(hello\\)"。
\\s,表示空格,s(space),包括制表符之类的