java深入正则表达式
(?:pattern)、(?=pattern)、(?<=pattern)、(?!pattern)和(?<!pattern)
import java.util.regex.Matcher;
import java.util.regex.Pattern;
public class RegexMatches
{
public static void main( String args[] ){
String password="Windows";
String regex="^(?=W)\\w+(?<=s)$";
Pattern p=Pattern.compile(regex);
Matcher m=p.matcher(password);
boolean isMatch=m.matches();
System.out.println(isMatch);
if (m.find( )) {
System.out.println("Found value: " + m.group(0) );
System.out.println("Found value: " + m.group(1) );
} else {
System.out.println("NO MATCH");
}
String password2="Windows";
String regex2="^\\w{1}(?=i)\\w+$";
Pattern p2=Pattern.compile(regex2);
Matcher m2=p2.matcher(password2);
boolean isMatch2=m2.matches();
System.out.println(isMatch2);
if (m2.find( )) {
System.out.println("Found value: " + m2.group(0) );
} else {
System.out.println("NO MATCH");
}
String password3="Windows";
String regex3="^(?!a)\\w+(?<!a)$";
Pattern p3=Pattern.compile(regex3);
Matcher m3=p.matcher(password3);
boolean isMatch3=m.matches();
System.out.println(isMatch3);
if (m3.find( )) {
System.out.println("Found value: " + m3.group(0) );
} else {
System.out.println("NO MATCH");
}
String password4="Windows";
String regex4="^\\w{1}(?!a)\\w+$";
Pattern p4=Pattern.compile(regex4);
Matcher m4=p4.matcher(password4);
boolean isMatch4=m4.matches();
System.out.println(isMatch4);
if (m4.find( )) {
System.out.println("Found value: " + m4.group(0) );
} else {
System.out.println("NO MATCH");
}
String password5="Windows";
String regex5="^\\w{1}(?:i)\\w+$";
Pattern p5=Pattern.compile(regex5);
Matcher m5=p5.matcher(password4);
boolean isMatch5=m5.matches();
System.out.println(isMatch5);
if (m5.find( )) {
System.out.println("Found value: " + m5.group(0) );
} else {
System.out.println("NO MATCH");
}
}
}
result
true
NO MATCH
true
NO MATCH
true
Found value: Windows
true
NO MATCH
true
NO MATCH
start 和 end 方法
import java.util.regex.Matcher;
import java.util.regex.Pattern;
public class RegexMatches
{
private static final String REGEX = "[4]*cat[123]*";
private static final String INPUT =
"cat1 cat2 cat3 cattie 4cat";
public static void main( String args[] ){
Pattern p = Pattern.compile(REGEX);
Matcher m = p.matcher(INPUT); // 获取 matcher 对象
int count = 0;
while(m.find()) {
count++;
System.out.println("Match number "+count);
System.out.println("start(): "+m.start());
System.out.println("end(): "+m.end());
System.out.println("group(): "+m.group());
}
}
}
包含：
import java.util.regex.*;
class RegexExample1{
public static void main(String args[]){
String content = "I am noob " +
"from runoob.com.";
String pattern = ".*runoob.*";
boolean isMatch = Pattern.matches(pattern, content);
System.out.println("字符串中是否包含了 'runoob' 子字符串? " + isMatch);
}
}
捕获组
import java.util.regex.Matcher;
import java.util.regex.Pattern;
public class RegexMatches
{
public static void main( String args[] ){
// 按指定模式在字符串查找
String line = "This order was placed for QT3000! OK?";
String pattern = "(\\D*)(\\d+)(.*)";
// 创建 Pattern 对象
Pattern r = Pattern.compile(pattern);
// 现在创建 matcher 对象
Matcher m = r.matcher(line);
if (m.find( )) {
System.out.println("Found value: " + m.group(0) );
System.out.println("Found value: " + m.group(1) );
System.out.println("Found value: " + m.group(2) );
System.out.println("Found value: " + m.group(3) );
} else {
System.out.println("NO MATCH");
}
}
}
result
Found value: This order was placed for QT3000! OK?
Found value: This order was placed for QT
Found value: 3000
Found value: ! OK?
matches 和 lookingAt 方法
import java.util.regex.Matcher;
import java.util.regex.Pattern;
public class RegexMatches
{
private static final String REGEX = "foo";
private static final String INPUT = "fooooooooooooooooo";
private static final String INPUT2 = "ooooofoooooooooooo";
private static Pattern pattern;
private static Matcher matcher;
private static Matcher matcher2;
public static void main( String args[] ){
pattern = Pattern.compile(REGEX);
matcher = pattern.matcher(INPUT);
matcher2 = pattern.matcher(INPUT2);
System.out.println("Current REGEX is: "+REGEX);
System.out.println("Current INPUT is: "+INPUT);
System.out.println("Current INPUT2 is: "+INPUT2);
System.out.println("lookingAt(): "+matcher.lookingAt());
System.out.println("matches(): "+matcher.matches());
System.out.println("lookingAt(): "+matcher2.lookingAt());
}
}
result
Current REGEX is: foo
Current INPUT is: fooooooooooooooooo
Current INPUT2 is: ooooofoooooooooooo
lookingAt(): true
matches(): false
lookingAt(): false
replaceFirst 和 replaceAll 方法
import java.util.regex.Matcher;
import java.util.regex.Pattern;
public class RegexMatches
{
private static String REGEX = "dog";
private static String INPUT = "The dog says meow. " +
"All dogs say meow.";
private static String REPLACE = "cat";
public static void main(String[] args) {
Pattern p = Pattern.compile(REGEX);
// get a matcher object
Matcher m = p.matcher(INPUT);
System.out.println(m.replaceFirst(REPLACE));
System.out.println(m.replaceAll(REPLACE));
System.out.println(INPUT);
}
}
result
The cat says meow. All dogs say meow.
The cat says meow. All cats say meow.
The dog says meow. All dogs say meow.
appendReplacement 和 appendTail 方法
import java.util.regex.Matcher;
import java.util.regex.Pattern;
public class RegexMatches
{
private static String REGEX = "a*b";
private static String INPUT = "aabfooaabfooabfoobkkk";
private static String REPLACE = "-";
public static void main(String[] args) {
Pattern p = Pattern.compile(REGEX);
// 获取 matcher 对象
Matcher m = p.matcher(INPUT);
StringBuffer sb = new StringBuffer();
while(m.find()){
m.appendReplacement(sb,REPLACE);
System.out.println("sb.toString():"+sb.toString()+",INPUT:"+INPUT);
}
m.appendTail(sb);
System.out.println(sb.toString());
}
}
result
sb.toString():-,INPUT:aabfooaabfooabfoobkkk
sb.toString():-foo-,INPUT:aabfooaabfooabfoobkkk
sb.toString():-foo-foo-,INPUT:aabfooaabfooabfoobkkk
sb.toString():-foo-foo-foo-,INPUT:aabfooaabfooabfoobkkk
-foo-foo-foo-kkk
