从头认识java-11.4 正则表达式（3）-Pattern和Matcher

这一章节我们来讨论一下Pattern和Matcher。

之前我们都是简单的使用正则表达式来匹配字符串，其实java里面提供了强大的正则匹配类，我们下面将以几个例子来说明。

package com.ray.ch11;

import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class Test {

public static void main(String[] args) {
String testStr = "abc";
String[] regulars = { "a", "abc", "//d","a?" };
System.out.println("input:" + testStr);
for (String item : regulars) {
Pattern pattern = Pattern.compile(item);
Matcher matcher = pattern.matcher(testStr);
while (matcher.find()) {
System.out.println("regular:" + item + " start:"
+ matcher.start() + " end:" + matcher.end());
}
}
}
}

输出：

input:abc
regular:a start:0 end:1
regular:abc start:0 end:3
regular:a? start:0 end:1
regular:a? start:1 end:1
regular:a? start:2 end:2
regular:a? start:3 end:3

从上面的输出可以看到，我们不但可以得到是否匹配的结果，而且通过matcher，我们可以得到很多其他的信息，例如上面的在那个位置匹配，在哪个位置终结。

我们下面改变一下输入，然后再改变一下规则看看另外一个例子：

package com.ray.ch11;

import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class Test {

public static void main(String[] args) {
String testStr = "java now has regular expression";
String[] regulars = { "^java", "\\Breg.*", "n.w\\s+h(a|i)s", "s?",
"s+", "s*", "s{4}", "s{1}", "s{1,3}" };
System.out.println("input:" + testStr);
for (String item : regulars) {
Pattern pattern = Pattern.compile(item);
Matcher matcher = pattern.matcher(testStr);
while (matcher.find()) {
System.out.println("regular:" + item + " start:"
+ matcher.start() + " end:" + matcher.end());
}
}
}
}

输出：

input:java now has regular expression
regular:^java start:0 end:4
regular:n.w\s+h(a|i)s start:5 end:12
regular:s? start:0 end:0
regular:s? start:1 end:1
regular:s? start:2 end:2
regular:s? start:3 end:3
regular:s? start:4 end:4
regular:s? start:5 end:5
regular:s? start:6 end:6
regular:s? start:7 end:7
regular:s? start:8 end:8
regular:s? start:9 end:9
regular:s? start:10 end:10
regular:s? start:11 end:12
regular:s? start:12 end:12
regular:s? start:13 end:13
regular:s? start:14 end:14
regular:s? start:15 end:15
regular:s? start:16 end:16
regular:s? start:17 end:17
regular:s? start:18 end:18
regular:s? start:19 end:19
regular:s? start:20 end:20
regular:s? start:21 end:21
regular:s? start:22 end:22
regular:s? start:23 end:23
regular:s? start:24 end:24
regular:s? start:25 end:25
regular:s? start:26 end:27
regular:s? start:27 end:28
regular:s? start:28 end:28
regular:s? start:29 end:29
regular:s? start:30 end:30
regular:s? start:31 end:31
regular:s+ start:11 end:12
regular:s+ start:26 end:28
regular:s* start:0 end:0
regular:s* start:1 end:1
regular:s* start:2 end:2
regular:s* start:3 end:3
regular:s* start:4 end:4
regular:s* start:5 end:5
regular:s* start:6 end:6
regular:s* start:7 end:7
regular:s* start:8 end:8
regular:s* start:9 end:9
regular:s* start:10 end:10
regular:s* start:11 end:12
regular:s* start:12 end:12
regular:s* start:13 end:13
regular:s* start:14 end:14
regular:s* start:15 end:15
regular:s* start:16 end:16
regular:s* start:17 end:17
regular:s* start:18 end:18
regular:s* start:19 end:19
regular:s* start:20 end:20
regular:s* start:21 end:21
regular:s* start:22 end:22
regular:s* start:23 end:23
regular:s* start:24 end:24
regular:s* start:25 end:25
regular:s* start:26 end:28
regular:s* start:28 end:28
regular:s* start:29 end:29
regular:s* start:30 end:30
regular:s* start:31 end:31
regular:s{1} start:11 end:12
regular:s{1} start:26 end:27
regular:s{1} start:27 end:28
regular:s{1,3} start:11 end:12
regular:s{1,3} start:26 end:28

解释：

（1）上面的find（）函数就像迭代器一样，迭代字符串里面每一个字符。而且find（int）里面还可以放置参数，来决定从第几个位置开始迭代。

（2）上面的start（）和end（）返回匹配的开始和结束的位置

除了上面的特性，我们还可以在pattern里面加上参数来限定匹配。

package com.ray.ch11;

import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class Test {

public static void main(String[] args) {
String testStr = "java now has regular expression\n"
+ "JAVA now has regular expression";
String[] regulars = { "^java" };
System.out.println("input:" + testStr);
for (String item : regulars) {
Pattern pattern = Pattern.compile(item, Pattern.CASE_INSENSITIVE
| Pattern.MULTILINE);
Matcher matcher = pattern.matcher(testStr);
while (matcher.find()) {
System.out.println("regular:" + item + " start:"
+ matcher.start() + " end:" + matcher.end() + " group:"
+ matcher.group());
}
}
}
}

输出：

input:java now has regular expression
JAVA now has regular expression
regular:^java start:0 end:4 group:java
regular:^java start:32 end:36 group:JAVA

总结：这一章节主要举例讲述了Pattern和Matcher。

这一章节就到这里，谢谢。

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