正则表达式
所有对于正则表达式的操作位于java.util.regex包下。
两个重要的类：Matcher Pattern
| package com.anllin.regex;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
public class Matches
{
public static void main(String[] args)
{
Matcher matcher = Pattern.compile("\\w+").matcher(
"this is a regex test, the fisrt program");
while (matcher.find())
{
System.out.println("[" + matcher.group() + "]");
}
System.out.println("---------------------------");
int i = 0;
while (matcher.find(i))
{
System.out.print("[" + matcher.group() + "]");
i++;
}
}
}
|
输出结果
| [this]
[is]
[a]
[regex]
[test]
[the]
[fisrt]
[program]
---------------------------
[this][his][is][s][is][is][s][a][a][regex][regex][egex][gex][ex][x][test][test][est][st][t][the][the][the][he][e][fisrt][fisrt][isrt][srt][rt][t][program][program][rogram][ogram][gram][ram][am][m] |
分组
| import java.util.regex.Matcher;
import java.util.regex.Pattern;
public class Group
{
public static void main(String[] args)
{
String statement = "this is a test about the regex group, the method groupCount is used";
Matcher m = Pattern.compile("(?m)(\\S+)\\s+((\\S+)\\s+(\\S+))")
.matcher(statement);
while (m.find())
{
for (int i = 0; i < m.groupCount(); i++)
{
System.out.println("[" + m.group(i) + "]");
}
}
}
} |
输出结果
| [this is a]
[this]
[is a]
[is]
[test about the]
[test]
[about the]
[about]
[regex group, the]
[regex]
[group, the]
[group,]
[method groupCount is]
[method]
[groupCount is]
[groupCount]
|
Start() 和end()的使用
| import java.util.regex.Matcher;
import java.util.regex.Pattern;
public class StartEnd
{
public static void main(String[] args)
{
String[] input = new String[] { "java has regular expressing in 1.4",
"regular expressing now expressing in java",
"java represses oracular expressions" };
Pattern p1 = Pattern.compile("re\\w*");
Pattern p2 = Pattern.compile("java.*");
for (int i = 0; i < input.length; i++)
{
System.out.println("input" + i + ":" + input[i]);
Matcher m1 = p1.matcher(input[i]);
Matcher m2 = p2.matcher(input[i]);
while (m1.find())
{
System.out.println("m1.find() [" + m1.group() + "] start = "
+ m1.start() + ",end = " + m1.end());
}
while (m2.find())
{
System.out.println("m2.find() [" + m2.group() + "] start = "
+ m2.start() + ",end = " + m2.end());
}
if(m1.lookingAt())
{
System.out.println("m1.lookingAt() [" + m1.group() + "] start = "
+ m1.start() + ",end = " + m1.end());
}
if(m2.lookingAt())
{
System.out.println("m2.lookingAt() [" + m2.group() + "] start = "
+ m2.start() + ",end = " + m2.end());
}
if(m1.matches())
{
System.out.println("m1.matches() [" + m1.group() + "] start = "
+ m1.start() + ",end = " + m1.end());
}
if(m2.matches())
{
System.out.println("m2.matches() [" + m2.group() + "] start = "
+ m2.start() + ",end = " + m2.end());
}
System.out.println();
}
}
}
|
输出结果：
| input0:java has regular expressing in 1.4
m1.find() [regular] start = 9,end = 16
m1.find() [ressing] start = 20,end = 27
m2.find() [java has regular expressing in 1.4] start = 0,end = 34
m2.lookingAt() [java has regular expressing in 1.4] start = 0,end = 34
m2.matches() [java has regular expressing in 1.4] start = 0,end = 34
input1:regular expressing now expressing in java
m1.find() [regular] start = 0,end = 7
m1.find() [ressing] start = 11,end = 18
m1.find() [ressing] start = 26,end = 33
m2.find() [java] start = 37,end = 41
m1.lookingAt() [regular] start = 0,end = 7
input2:java represses oracular expressions
m1.find() [represses] start = 5,end = 14
m1.find() [ressions] start = 27,end = 35
m2.find() [java represses oracular expressions] start = 0,end = 35
m2.lookingAt() [java represses oracular expressions] start = 0,end = 35
m2.matches() [java represses oracular expressions] start = 0,end = 35
|
模式标记
public static Pattern compile(String regex,int flags)
| import java.util.regex.Matcher;
import java.util.regex.Pattern;
public class Flag
{
public static void main(String[] args)
{
Pattern p = Pattern.compile("^java", Pattern.CASE_INSENSITIVE
| Pattern.MULTILINE);
Matcher m = p.matcher("java has regex \njava has regex \n"
+ "JAVA has pretty good regular expressions\n"
+ "Regular expressions are in java");
while (m.find())
{
System.out.println(m.group());
}
}
} |
| 输出结果： java
java
JAVA
|
Split()方法的使用
public String[] split(CharSequence input,int limit)
public String[] split(CharSequence input)
| import java.util.Arrays;
import java.util.regex.Pattern;
public class SplitDemo
{
public static void main(String[] args)
{
String input = "This!!unusual use!!of exclamation!!points";
System.out.println(Arrays.asList(Pattern.compile("!!").split(input)));
System.out
.println(Arrays.asList(Pattern.compile("!!").split(input, 3)));
System.out.println(Arrays.asList("Aha! String has a split() built in"
.split(" ")));
}
} |
输出结果：
| [This, unusual use, of exclamation, points]
[This, unusual use, of exclamation!!points]
[Aha!, String, has, a, split(), built, in]
|
替换操作
| import java.io.BufferedReader;
import java.io.FileInputStream;
import java.io.InputStreamReader;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
public class ReplaceTest
{
public static void main(String[] args) throws Exception
{
BufferedReader reader = new BufferedReader(new InputStreamReader(
new FileInputStream("src/com/anllin/regex/ReplaceTest.java")));
String str = null;
StringBuffer sb = new StringBuffer();
while (null != (str = reader.readLine()))
{
sb.append(str);
}
String s = sb.toString();
// Match the specially-commented block of text above:
Matcher mInput = Pattern.compile("/\\*!(.*)!\\*/", Pattern.DOTALL)
.matcher(s);
if (mInput.find())
{
// Captured by parentheses
s = mInput.group(1);
}
// Replace two or more spaces with a single space:
s = s.replaceAll(" {2,}", " ");
// Replace one or more spaces at the beginning of each line with no
// spaces.Must enable MULTILINE mode.
s = s.replaceAll("(?m)^+", "");
System.out.println(s);
s = s.replaceFirst("[aeiou]", "(VOWEL1)");
StringBuffer sbuf = new StringBuffer();
Pattern p = Pattern.compile("[aeiou]");
Matcher m = p.matcher(s);
// Process the find information as you perform the replacements:
while (m.find())
{
m.appendReplacement(sbuf, m.group().toUpperCase());
}
// Put in the remainder of ther text:
m.appendTail(sbuf);
System.out.println(sbuf);
}
} |
输出结果
| package com.anllin.regex;import java.io.BufferedReader;import java.io.FileInputStream;import java.io.InputStreamReader;import java.util.regex.Matcher;import java.util.regex.Pattern;public class ReplaceTest{ public static void main(String[] args) throws Exception { BufferedReader reader = new BufferedReader(new InputStreamReader( new FileInputStream("src/com/anllin/regex/ReplaceTest.java"))); String str = null; StringBuffer sb = new StringBuffer(); while (null != (str = reader.readLine())) { sb.append(str); } String s = sb.toString(); // Match the specially-commented block of text above: Matcher mInput = Pattern.compile("/\\*!(.*)!\\*/", Pattern.DOTALL) .matcher(s); if (mInput.find()) { // Captured by parentheses s = mInput.group(1); } // Replace two or more spaces with a single space: s = s.replaceAll(" {2,}", " "); // Replace one or more spaces at the beginning of each line with no // spaces.Must enable MULTILINE mode. s = s.replaceAll("(?m)^+", ""); System.out.println(s); s = s.replaceFirst("[aeiou]", "(VOWEL1)"); StringBuffer sbuf = new StringBuffer(); Pattern p = Pattern.compile("[aeiou]"); Matcher m = p.matcher(s); // Process the find information as you perform the replacements: while (m.find()) { m.appendReplacement(sbuf, m.group().toUpperCase()); } // Put in the remainder of ther text: m.appendTail(sbuf); System.out.println(sbuf); }}
--------------------------------------------------------------------
p(VOWEL1)ckAgE cOm.AnllIn.rEgEx;ImpOrt jAvA.IO.BUffErEdREAdEr;ImpOrt jAvA.IO.FIlEInpUtStrEAm;ImpOrt jAvA.IO.InpUtStrEAmREAdEr;ImpOrt jAvA.UtIl.rEgEx.MAtchEr;ImpOrt jAvA.UtIl.rEgEx.PAttErn;pUblIc clAss REplAcETEst{ pUblIc stAtIc vOId mAIn(StrIng[] Args) thrOws ExcEptIOn { BUffErEdREAdEr rEAdEr = nEw BUffErEdREAdEr(nEw InpUtStrEAmREAdEr( nEw FIlEInpUtStrEAm("src/cOm/AnllIn/rEgEx/REplAcETEst.jAvA"))); StrIng str = nUll; StrIngBUffEr sb = nEw StrIngBUffEr(); whIlE (nUll != (str = rEAdEr.rEAdLInE())) { sb.AppEnd(str); } StrIng s = sb.tOStrIng(); // MAtch thE spEcIAlly-cOmmEntEd blOck Of tExt AbOvE: MAtchEr mInpUt = PAttErn.cOmpIlE("/\\*!(.*)!\\*/", PAttErn.DOTALL) .mAtchEr(s); If (mInpUt.fInd()) { // CAptUrEd by pArEnthEsEs s = mInpUt.grOUp(1); } // REplAcE twO Or mOrE spAcEs wIth A sInglE spAcE: s = s.rEplAcEAll(" {2,}", " "); // REplAcE OnE Or mOrE spAcEs At thE bEgInnIng Of EAch lInE wIth nO // spAcEs.MUst EnAblE MULTILINE mOdE. s = s.rEplAcEAll("(?m)^+", ""); SystEm.OUt.prIntln(s); s = s.rEplAcEFIrst("[AEIOU]", "(VOWEL1)"); StrIngBUffEr sbUf = nEw StrIngBUffEr(); PAttErn p = PAttErn.cOmpIlE("[AEIOU]"); MAtchEr m = p.mAtchEr(s); // PrOcEss thE fInd InfOrmAtIOn As yOU pErfOrm thE rEplAcEmEnts: whIlE (m.fInd()) { m.AppEndREplAcEmEnt(sbUf, m.grOUp().tOUppErCAsE()); } // PUt In thE rEmAIndEr Of thEr tExt: m.AppEndTAIl(sbUf); SystEm.OUt.prIntln(sbUf); }}
|
Reset()方法的使用
| import java.util.regex.Matcher;
import java.util.regex.Pattern;
public class ResetTest
{
public static void main(String[] args)
{
Matcher m = Pattern.compile("[frb][aiu][gx]").matcher(
"fix the rug with bags");
while (m.find())
{
System.out.println(m.group());
}
m.reset("fix the rig with rags");
while (m.find())
{
System.out.println(m.group());
}
}
} |
Output:
| fix
rug
bag
fix
rig
rag
|
| Summary of regular-expression constructs
|
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