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Home Java javaTutorial What is the usage of regular expression in java

What is the usage of regular expression in java

Oct 29, 2020 am 11:22 AM
java regular expression

java正則表達式用法:1、使用Pattern類進行字符串的拆分,使用的方法是【String[] split(CharSequence input)】;2、使用Matcher類進行字符串的驗證和替換。

What is the usage of regular expression in java

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java正則表達式用法:

正則表達式是一種可以用于模式匹配和替換的規(guī)范,一個正則表達式就是由普通的字符(例如字符a到z)以及特殊字符(元字符)組成的文字模式,它 用以描述在查找文字主體時待匹配的一個或多個字符串。正則表達式作為一個模板,將某個字符模式與所搜索的字符串進行匹配。

一個正則表達式就是由普通的字符(例如字符a到z)以及特殊字符(元字符)組成的文字模式,它 用以描述在查找文字主體時待匹配的一個或多個字符串。正則表達式作為一個模板,將某個字符模式與所搜索的字符串進行匹配。

*下面是java中正則表達式常用的語法:

字符的取值范圍
1.[abc]?:?表示可

3.[a-zA-Z]:?表示是英文字母
4.[0-9]:表示是數(shù)字

簡潔的字符表示
.:匹配任意的字符
\d:表示數(shù)字
\D:表示非數(shù)字
\s:表示由空字符組成,[?\t\n\r\x\f]
\S:表示由非空字符組成,[^\s]
\w:表示字母、數(shù)字、下劃線,[a-zA-Z0-9_]
\W:表示不是由字母、數(shù)字、下劃線組成

數(shù)量表達式
1.?:?表示出現(xiàn)0次或1次
2.+:?表示出現(xiàn)1次或多次
3.*:?表示出現(xiàn)0次、1次或多次
4.{n}:表示出現(xiàn)n次
5.{n,m}:表示出現(xiàn)n~m次
6.{n,}:表示出現(xiàn)n次或n次以上

邏輯表達式
1.XY:?表示X后面跟著Y,這里X和Y分別是正則表達式的一部分
2.X|Y:表示X或Y,比如"food|f"匹配的是foo(d或f),而"(food)|f"匹配的是food或f
3.(X):子表達式,將X看做是一個整體

java中提供了兩個類來支持正則表達式的操作
分別是java.util.regex下的Pattern類和Matcher類
使用Pattern類進行字符串的拆分,使用的方法是String[]?split(CharSequence?input)
使用Matcher類進行字符串的驗證和替換,
匹配使用的方法是boolean?matches()
替換使用的方法是?String?replaceAll(String?replacement)

Pattern類的構(gòu)造方法是私有的
所以我們使用Pattern?p?=?Pattern.compile("a*b");進行實例化
Matcher類的實例化依賴Pattern類的對象Matcher?m?=?p.matcher("aaaaab");

在實際的開發(fā)中,為了方便我們很少直接使用Pattern類或Matcher類,而是使用String類下的方法
驗證:boolean?matches(String?regex)
拆分:?String[]?split(String?regex)
替換:?String?replaceAll(String?regex,?String?replacement)

?下面是正則表達式的簡單使用:

1、Test01.java :使用正則表達式使代碼變得非常簡潔。

 1 package test_regex;
 2 public class Test01 {
 3     public static void main(String[] args){
 4         String str = "1234567";
 5 //        char[] c = str.toCharArray();
 6 //        boolean b = true;
 7 //        for(char c1:c){
 8 //            if(!(c1>=&#39;0&#39;&&c1<=&#39;9&#39;)){
 9 //                b = false;
10 //                break;
11 //            }
12 //        }
13 //        System.out.println(b);
14 
15         String regex = "\\d+";
16         System.out.println(str.matches(regex));
17     }
18 }

2、TestMatcher01.java(Matcher類的使用,用于字符串的驗證)

 1 package test_regex;
 2 import java.util.regex.Pattern;
 3 import java.util.regex.Matcher;
 4 public class TestMatcher01 {
 5     public static void main(String[] args){
 6         String str = "1234567abc";
 7         String regex = "\\w{10,}";
 8 //        Pattern pat = Pattern.compile(regex);
 9 //        Matcher mat = pat.matcher(str);
10 //        System.out.println(mat.matches());
11         System.out.println(str.matches(regex));
12     }
13 }

3、TestMatcher02.java(Matcher類的使用,用于字符串的替換)

 1 package test_regex;
 2 import java.util.regex.Pattern;
 3 import java.util.regex.Matcher;
 4 public class TestMatcher02 {
 5     public static void main(String[] args){
 6         String str = "12Y34h56dAd7";
 7         String regex = "[a-zA-Z]+";
 8 //        Pattern pat = Pattern.compile(regex);
 9 //        Matcher mat = pat.matcher(str);
10 //        System.out.println(mat.replaceAll(":"));
11         System.out.println(str.replaceAll(regex,"-"));
12     }
13 }

4、TestPattern01.java(Pattern類的使用,用于字符串的拆分)

 1 package test_regex;
 2 import java.util.regex.Pattern;
 3 public class TestPattern01 {
 4     public static void main(String[] args){
 5         String str = "Tom:30|Jerry:20|Bob:25";
 6         String regex = "\\|";
 7 //        Pattern pat = Pattern.compile(regex);
 8 //        String[] arr = pat.split(str);
 9         String[] arr = str.split(regex);
10         for(String s:arr){
11             System.out.println(s);
12         }
13     }
14 }

5、TestRegex01.java(大概判斷一個郵箱地址是否合法)

 1 package test_regex;
 2 public class TestRegex01 {
 3     //判斷一個郵箱地址是否合法
 4     public static void main(String[] args){
 5         //這里默認郵箱的后綴是.com或.net.cn
 6         String str = "aa@aa.net.cn";
 7         String regex = "\\w+@\\w+\\.(com|net.cn)";
 8         System.out.println(str.matches(regex));
 9     }
10 }

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