(1)正则基础

包：java.util.regex

相关类：Pattern，Matcher，PatternSyntaxException

1. JDK API例子：

典型的调用顺序是 （*表示出现0次或多次；例子表示aaaaab是否匹配a*b格式）

 Pattern p = Pattern.("a*b");
 Matcher m = p.("aaaaab");
 boolean b = m.();compilematchermatches

在仅使用一次正则表达式时，可以方便地通过此类定义 matches 方法。此方法编译表达式并在单个调用中将输入序列与其匹配。语句

 boolean b = Pattern.matches("a*b","aaaaab");

String类的方法：

      public boolean matches(Stringregex)

      boolean b = "aaaaab".matches("a*b");

2.常用简单方法（一些方法在String类中有实现）

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

public class RegexExamples {

	public static void main(String[] args) {
		// using pattern with flags
		Pattern pattern = Pattern.compile("ab",Pattern.CASE_INSENSITIVE);
		Matcher matcher = pattern.matcher("ABcabdAb");
		// using Matcher find(),group(),start() and end() methods
		while (matcher.find()) {
			System.out.println("Found the text "" + matcher.group()
					+ "" starting at " + matcher.start()
					+ " index and ending at index " + matcher.end());
		}

		// using Pattern split() method
		pattern = Pattern.compile("W");
		String[] words = pattern.split("one@two#three:four$five");
		System.out.print("Split using Pattern.split(): ");
		for (String s : words) {
			System.out.print(s + " ");
		}
		System.out.println();
		words = "one@two#three:four$five".split("W");
		System.out.print("Split using String.split(): ");
		for (String s : words) {
			System.out.print(s + " ");
		}
		System.out.println();

		// using Matcher.replaceFirst() and replaceAll() methods
		pattern = Pattern.compile("1*2");
		matcher = pattern.matcher("112345126782");
		System.out.println("Using matcher.replaceAll: "
				+ matcher.replaceAll("_"));
		System.out.println("Using matcher.replaceFirst: "
				+ matcher.replaceFirst("_"));

		System.out.println("Using String.replaceAll: "
				+ "112345126782".replaceAll("1*2","_"));
		System.out.println("Using String.replaceFirst: "
				+ "112345126782".replaceFirst("1*2","_"));
	}

}

输出：

Found the text "AB" starting at 0 index and ending at index 2
Found the text "ab" starting at 3 index and ending at index 5
Found the text "Ab" starting at 6 index and ending at index 8
Split using Pattern.split(): one two three four five 
Split using String.split(): one two three four five 
Using matcher.replaceAll: _345_678_
Using matcher.replaceFirst: _345126782
Using String.replaceAll: _345_678_
Using String.replaceFirst: _345126782

3. 常用语法（API）

几个例子

public class RegexExpression {
	
	public static void main(String[] args) {
		System.out.println(""a".matches("[abc]") --> 匹配a/b/c： "
				+ "a".matches("[abc]"));
		System.out.println(""aab".matches("[abc]+") --> a/b/c出现一次或多次： "
				+ "aab".matches("[abc]+"));
		System.out.println("" @aab".matches("sW?w{1,5}") --> 空白字符+非单词字符至多一次+单词字符1到5次： "
				+ " @aab".matches("sW?w{1,5}"));
		System.out.println(""xa@c2".matches("^[^abc].+[123]$") --> 非a/b/c开头+任意字符1次或多次+1/2/3结尾： "
				+ "xa@c2".matches("^[^abc].+[123]$"));
		
	}
}

输出：

"a".matches("[abc]") --> 匹配a/b/c： true
"aab".matches("[abc]+") --> a/b/c出现一次或多次： true
" @aab".matches("sW?w{1,5}") --> 空白字符+非单词字符至多一次+单词字符1到5次： true
"xa@c2".matches("^[^abc].+[123]$") --> 非a/b/c开头+任意字符1次或多次+1/2/3结尾： true

（编辑：李大同）

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