在JAVA中使用正则表达式

jdk1.4中加入了java.util.regex包提供对正则表达式的支持。而且Java.lang.String类中的replaceAll和split函数也是调用的正则表达式来实现的。 
正则表达式对字符串的操作主要包括：字符串匹配，指定字符串替换，指定字符串查找和字符串分割。下面就用一个例子来说明这些操作是如何实现的：

<%@ page import="java.util.regex.*"%> 
<% 
Pattern p=null; //正则表达式 
Matcher m=null; //操作的字符串 
boolean b; 
String s=null; 
StringBuffer sb=null; 
int i=0; 
//字符串匹配，这是不符合的 
p = Pattern.compile("a*b"); 
m = p.matcher("baaaaab"); 
b = m.matches(); 
out.println("字符串\"baaaaab\"是否匹配正则表达式\"a*b\": "+b+"<br>");

//字符串匹配，这是符合的 
p = Pattern.compile("a*b"); 
m = p.matcher("aaaaab"); 
b = m.matches(); 
out.println("字符串\"aaaaab\"是否匹配正则表达式\"a*b\": "+b+"<br>");

//字符串替换 
p = Pattern.compile("ab"); 
m = p.matcher("aaaaab"); 
s = m.replaceAll("d"); 
out.println(s+"<br>"); 
p = Pattern.compile("a*b"); 
m = p.matcher("aaaaab"); 
s = m.replaceAll("d"); 
out.println(s+"<br>"); 
p = Pattern.compile("a*b"); 
m = p.matcher("caaaaab"); 
s = m.replaceAll("d"); 
out.println(s+"<br>");

//字符串查找并替换 
p = Pattern.compile("cat"); 
m = p.matcher("one cat two cats in the yard"); 
sb = new StringBuffer(); 
while (m.find()) { 
m.appendReplacement(sb, "dog"); 
i++; 
} 
m.appendTail(sb); 
out.println(sb.toString()+"<br>"); 
out.println(i+"<br>");

i=0; 
p = Pattern.compile("cat"); 
m = p.matcher("one cat two ca tsi nthe yard"); 
sb = new StringBuffer(); 
while (m.find()) { 
m.appendReplacement(sb, "dog"); 
i++; 
} 
m.appendTail(sb); 
out.println(sb.toString()+"<br>"); 
out.println(i+"<br>");

p = Pattern.compile("cat"); 
m = p.matcher("one cat two cats in the yard"); 
p=m.pattern(); 
m = p.matcher("bacatab"); 
b = m.matches(); 
out.println(b+"<br>"); 
s = m.replaceAll("dog"); 
out.println(s+"<br>");

 

i=0; 
p = Pattern.compile("(fds){2,}"); 
m = p.matcher("dsa da fdsfds aaafdsafds aaf"); 
sb = new StringBuffer(); 
while (m.find()) { 
m.appendReplacement(sb, "dog"); 
i++; 
} 
m.appendTail(sb); 
out.println(sb.toString()+"<br>"); 
out.println(i+"<br>");

//将cat加红色显示 
p = Pattern.compile("cat"); 
m = p.matcher("one cat two cats in the yard"); 
sb = new StringBuffer(); 
while (m.find()) { 
m.appendReplacement(sb, "<font color=\"red\">cat</font>"); 
} 
m.appendTail(sb); 
out.println(sb.toString()+"<br>"); 
String aa=sb.toString(); 
out.println(aa+"<br>");

//字符串分割 
p = Pattern.compile("a+"); 
String[] a=p.split("caaaaaat"); 
for(i=0;i<a.length;i++) 
{ 
out.println(a[i]+"<br>"); 
}

p = Pattern.compile("a+"); 
a=p.split("c aa aaaa t",0); 
for(i=0;i<a.length;i++) 
{ 
out.println(a[i]+"<br>"); 
}

//以空格分隔 
p = Pattern.compile(" +"); 
a=p.split("c aa aaaa t",0); 
for(i=0;i<a.length;i++) 
{ 
out.println(a[i]+"<br>"); 
} 
//以加号分隔 
p = Pattern.compile("\\+"); 
a=p.split("dsafasdfdsafsda+dsagfasdfa+sdafds"); 
out.println(a.length+"<br>"); 
for(i=0;i<a.length;i++) 
{ 
out.println(a[i]+"<br>"); 
} 
%>