一般来说比起功能有限的String类，我们更愿意构造功能强大的正则表达式。我们可以通过Pattern 与 Matcher 来构建功能强大的正则表达式
import java.io.File;
import java.io.FileNotFoundException;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.Scanner;
import java.util.regex.Matcher;
import java.util.regex.Pattern;public class Main {//public static String s = "I am a good student... haha good";public static void main(String[] args) throws FileNotFoundException {Scanner input = new Scanner(new File("data.in"));Pattern tp = Pattern.compile(" ");System.out.println(Arrays.asList(tp.split("a b c")));String s = "abcabcabcdefabc";List<String> s1 = new ArrayList<String>();s1.add("abcabcabcdefabc"); s1.add("abc");s1.add("(abc)+"); s1.add("(abc){2,}");for (String s2 : s1) {System.out.println("正则：" + s2);Pattern p = Pattern.compile(s2); //编译自己的正则返回Pattern对象 ，Pattern对象表示编译后的正则表达式Matcher m = p.matcher(s); //传入要检索的字符串，返回Matcher对象while (m.find()) {System.out.println("Match : " + m.group() + " " + m.start() + " " + m.end());}}/** Pattern对象还提供了matches方法返回是否匹配整个字符串* split分割方法* * Matcher 提供方法：* matches用来判断整个输入字符串是否匹配正则表达式* lookingAt则用来判断该字符串的始部是否能够匹配模式* find 遍历输入字符串* */}
}输出：
[a, b, c]
正则：abcabcabcdefabc
Match : abcabcabcdefabc 0 15
正则：abc
Match : abc 0 3
Match : abc 3 6
Match : abc 6 9
Match : abc 12 15
正则：(abc)+
Match : abcabcabc 0 9
Match : abc 12 15
正则：(abc){2,}
Match : abcabcabc 0 9
组： 关于组的操作
组号为0表示表示整个表达式， 组号为1表示第一对括号
import java.io.File;
import java.io.FileNotFoundException;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.Scanner;
import java.util.regex.Matcher;
import java.util.regex.Pattern;public class Main {public static String s = "I am a good student\n" + "fhhj hhh nnnn oj\n" + "very am you can\n" ;public static void main(String[] args) throws FileNotFoundException {Matcher m = Pattern.compile("(?m)(\\S+)\\s+((\\S+)\\s+(\\S+)\\s+)$").matcher(s);while (m.find()) {for (int i = 0; i <= m.groupCount(); ++i) {System.out.print("[" + m.group(i) + "]");}System.out.println();}}
}
Pattern的split分割：
public class Main {public static String s = "I am a good student";public static void main(String[] args) throws FileNotFoundException {System.out.println( Arrays.asList(Pattern.compile(" ").split(s)));}
}
替换操作：
import java.io.File;
import java.io.FileNotFoundException;
import java.lang.reflect.Array;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.Scanner;
import java.util.regex.Matcher;
import java.util.regex.Pattern;public class Main {public static String s = "/*! here's a block of text to use as input to" +"the ruguler expresssion mavherer . note that we'll"+"extracted block.!*/";public static void main(String[] args) throws FileNotFoundException {Matcher m = Pattern.compile("/\\*!(.*)!\\*/").matcher(s);String ans = null;while (m.find()) {ans = m.group(1);}System.out.println("去掉注释符之后:" + ans);ans = ans.replaceAll(" {2,}", " ");System.out.println("去掉多余空格之后:" + ans);ans = ans.replaceAll("(?m)^ +", "");System.out.println("去掉前边的空格之后:" + ans);String tmp = ans.replaceAll("[aeiou]", "HAHA");System.out.println("替换之后:" + tmp);StringBuffer sb = new StringBuffer();Pattern p = Pattern.compile("[aeiou]");Matcher tm = p.matcher(ans);while (tm.find()) {/** 首先把要发生替换的部分到字符串开始的地方都复制给sb* 这里我们能够更加灵活的对发生替换的部分进行处理，我们这里的处理是转化成大写字母*/tm.appendReplacement(sb, tm.group().toUpperCase()); //System.out.println("SB = " + sb); 可以自己输出看一看}tm.appendTail(sb); //把末尾的部分加上System.out.println("替换之后:" + sb);}
}输出：
去掉注释符之后: here's a block of text to use as input tothe ruguler expresssion mavherer . note that we'llextracted block.
去掉多余空格之后: here's a block of text to use as input tothe ruguler expresssion mavherer . note that we'llextracted block.
去掉前边的空格之后:here's a block of text to use as input tothe ruguler expresssion mavherer . note that we'llextracted block.
替换之后:hHAHArHAHA's HAHA blHAHAck HAHAf tHAHAxt tHAHA HAHAsHAHA HAHAs HAHAnpHAHAt tHAHAthHAHA rHAHAgHAHAlHAHAr HAHAxprHAHAsssHAHAHAHAn mHAHAvhHAHArHAHAr . nHAHAtHAHA thHAHAt wHAHA'llHAHAxtrHAHActHAHAd blHAHAck.
替换之后:hErE's A blOck Of tExt tO UsE As InpUt tOthE rUgUlEr ExprEsssIOn mAvhErEr . nOtE thAt wE'llExtrActEd blOck.
我们可以用reset，将现有的Matcher对象应用于一个新的字符序列
public class Main {public static void main(String[] args) throws FileNotFoundException {List<String> list = new ArrayList<String>();list.add("string"); list.add("Scdvffv njnjn");list.add("test grgrg"); list.add("common gfgrg");Pattern p = Pattern.compile("^[Ssct]\\w+");Matcher m = p.matcher("");for (String s : list) {m.reset(s);while (m.find()) {//首先输出匹配字符串， 查看开始部分是否满足， 查看整个字符串是否满足System.out.println(m.group() + " " + m.lookingAt() +" " + m.matches());}}}
}
输出：string true true
Scdvffv true false
test true false
common true false
