在Java中使用正则表达式

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　　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。

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　　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：

<table width="100%" bgColor=#ffffff> <tr> <td>＜%@ 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(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(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
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＞");

p = Pattern.compile("cat");
m = p.matcher("one cat two cats in the yard");
sb = new StringBuffer();
while (m.find()) {
m.appendRep lacement(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＞");
}
p = Pattern.compile(" +");
a=p.split("c aa aaaa t",0);
for(i=0;i＜a.length;i++)
{
out.println(a[i]+"＜br＞");
}
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＞");
}
%＞
</td></tr></table>