常用正则表达式
常用字符
普通字符
普通字符主要讲解以下内容,并举例说明
- // String regStr = "[a-z]";//匹配a-z中任意一个字符
- // String regStr = "[A-Z]";//匹配A-Z中任何一个字符
- // String regStr = "abc";//匹配字符串abc
- // String regStr = "(?i)abc";//匹配字母abc不区分大小写
- // String regStr = "[0-9]";//匹配0-9任何一个字符
- // String regStr = "[^0-9]";//匹配不是0-9中的任何一个字符
- // String regStr = "[^0-9]{2}";//匹配2个不是0-9的字符
- // String regStr = "\\d";//匹配任何一个数字字符,等价于[0-9]
- // String regStr = "\\D";//匹配任何一个非数字字符,等价于[^0-9]
- // String regStr = "\\w";//匹配任何一个数字、字母、下划线,等价于[0-9a-zA-Z_]
- // String regStr = "\\W";//匹配任何一个除了数字、字母、下划线,等价于[^0-9a-zA-Z_]
- // String regStr = "\\s";//匹配任何一个空字符
- // String regStr = "\\S";//匹配任何一个非空字符
- // String regStr = "ab|cd";//选择匹配符,匹配字符串ab或者cd
1) String regStr = "[a-z]";//匹配a-z中任意一个字符
- @Test
- public void test1() {
- String str = "abc2021";
- String regStr = "[a-z]";
- Pattern compile = Pattern.compile(regStr);
- Matcher matcher = compile.matcher(str);
- while(matcher.find()){
- System.out.println("匹配到的数据为:"+matcher.group(0));
- }
- }
结果展示
2) String regStr = "[A-Z]";//匹配A-Z中任何一个字符
- @Test
- public void test2(){
- String str = "ABCabc2021";
- String regStr = "[A-Z]";
- Pattern compile = Pattern.compile(regStr);
- Matcher matcher = compile.matcher(str);
- while(matcher.find()){
- System.out.println("匹配到的数据为:"+matcher.group(0));
- }
- }
结果展示
3)String regStr = "abc";//匹配字符串abc
- @Test
- public void test2(){
- String str = "ABCabc2021";
- String regStr = "abc";
- Pattern compile = Pattern.compile(regStr);
- Matcher matcher = compile.matcher(str);
- while(matcher.find()){
- System.out.println("匹配到的数据为:"+matcher.group(0));
- }
- }
结果展示
4)String regStr = "(?i)abc";//匹配字母abc不区分大小写
- @Test
- public void test2(){
- String str = "ABCabc2021";
- String regStr = "(?i)abc";
- Pattern compile = Pattern.compile(regStr);
- Matcher matcher = compile.matcher(str);
- while(matcher.find()){
- System.out.println("匹配到的数据为:"+matcher.group(0));
- }
- }
结果展示
5) String regStr = "[0-9]";//匹配0-9任何一个字符
- @Test
- public void test2(){
- String str = "ABCabc2021";
- String regStr = "[0-9]";
- Pattern compile = Pattern.compile(regStr);
- Matcher matcher = compile.matcher(str);
- while(matcher.find()){
- System.out.println("匹配到的数据为:"+matcher.group(0));
- }
- }
结果展示
6) String regStr = "[^0-9]";//匹配不是0-9中的任何一个字符
- @Test
- public void test2(){
- String str = "ABCabc2021";
- String regStr = "[^0-9]";
- Pattern compile = Pattern.compile(regStr);
- Matcher matcher = compile.matcher(str);
- while(matcher.find()){
- System.out.println("匹配到的数据为:"+matcher.group(0));
- }
- }
结果展示
限定符
-
1) *:表示出现任意次数,0次或者n次
- @Test
- public void test2(){
- String str = "zypabcabc2021";
- String regStr = "zyp(abc)*";
- Pattern compile = Pattern.compile(regStr);
- Matcher matcher = compile.matcher(str);
- while(matcher.find()){
- System.out.println("匹配到的数据为:"+matcher.group(0));
- }
- }
结果展示
2)+:表示出现至少1次或者n次,如(abc)+表示abc出现1次或者多次
- @Test
- public void test2(){
- String str = "zypabc2021";
- String regStr = "zyp(abc)+";
- Pattern compile = Pattern.compile(regStr);
- Matcher matcher = compile.matcher(str);
- while(matcher.find()){
- System.out.println("匹配到的数据为:"+matcher.group(0));
- }
- }
结果展示
3)?:表示出现至少0次或者1次,如abc?表示c出现0次或者1次
- @Test
- public void test2(){
- String str = "zyp2021";
- String regStr = "zyp(abc)?";
- Pattern compile = Pattern.compile(regStr);
- Matcher matcher = compile.matcher(str);
- while(matcher.find()){
- System.out.println("匹配到的数据为:"+matcher.group(0));
- }
- }
结果展示
4){n}:表示出现n次,如[0-9]{2},表示匹配2次数字
- @Test
- public void test2(){
- String str = "zyp2021";
- String regStr = "[0-9]{2}";
- Pattern compile = Pattern.compile(regStr);
- Matcher matcher = compile.matcher(str);
- while(matcher.find()){
- System.out.println("匹配到的数据为:"+matcher.group(0));
- }
- }
结果展示
5){n,}表示至少出现n次,如[0-9]{3,}表示匹配至少3次数字
- @Test
- public void test2(){
- String str = "zyp2021";
- String regStr = "[0-9]{2,}";
- Pattern compile = Pattern.compile(regStr);
- Matcher matcher = compile.matcher(str);
- while(matcher.find()){
- System.out.println("匹配到的数据为:"+matcher.group(0));
- }
- }
结果展示
6){n,m}表示出现至少n次,最多m次,如[0-9]{2,4}表示匹配次数2-4次数字
- @Test
- public void test2(){
- String str = "zyp2021";
- String regStr = "[0-9]{2,4}";
- Pattern compile = Pattern.compile(regStr);
- Matcher matcher = compile.matcher(str);
- while(matcher.find()){
- System.out.println("匹配到的数据为:"+matcher.group(0));
- }
- }
结果展示
定位符
-
1) ^:表示字符串以什么开头的意思
- @Test
- public void test2(){
- String str = "2021zyp";
- String regStr = "^[0-9]+";
- Pattern compile = Pattern.compile(regStr);
- Matcher matcher = compile.matcher(str);
- while(matcher.find()){
- System.out.println("匹配到的数据为:"+matcher.group(0));
- }
- }
结果展示
2) $:表示字符串以什么结束的意思
- @Test
- public void test2(){
- String str = "2021zyp";
- String regStr = "[0-9]$";
- Pattern compile = Pattern.compile(regStr);
- Matcher matcher = compile.matcher(str);
- while(matcher.find()){
- System.out.println("匹配到的数据为:"+matcher.group(0));
- }
- }
没有匹配到,因为要以数字结束
3) \\b:表示边缘匹配(字符串的结尾或者空格之后)
- @Test
- public void test2(){
- String str = "zyp2021zyp";
- String regStr = "zyp\\b";
- Pattern compile = Pattern.compile(regStr);
- Matcher matcher = compile.matcher(str);
- while(matcher.find()){
- System.out.println("匹配到的数据为:"+matcher.group(0));
- }
- }
匹配到的是最后一个“zyp”
4) \\B:与\\b相反
- @Test
- public void test2(){
- String str = "zyp2021zyp";
- String regStr = "zyp\\B";
- Pattern compile = Pattern.compile(regStr);
- Matcher matcher = compile.matcher(str);
- while(matcher.find()){
- System.out.println("匹配到的数据为:"+matcher.group(0));
- }
- }
匹配到的是第一个“zyp”
分组
-
捕获分组
1)如(\\d\\d)(\\d\\d)表示匹配4位数字,如果字符串为2021abcd,
- @Test
- public void test2(){
- String str = "2021abcd";
- String regStr = "(\\d\\d)(\\d\\d)";
- Pattern compile = Pattern.compile(regStr);
- Matcher matcher = compile.matcher(str);
- while(matcher.find()){
- System.out.println("matcher.group(0):"+matcher.group(0));
- System.out.println("分组一:matcher.group(1):"+matcher.group(1));
- System.out.println("分组二:matcher.group(2):"+matcher.group(2));
- }
- }
结果展示
结论:由此可见()会将正则分组,并按顺序给出编号,从1开始
2) (?
- @Test
- public void test2(){
- String str = "2021abcd";
- String regStr = "(?
\\d\\d)(?\\d\\d)" ; - Pattern compile = Pattern.compile(regStr);
- Matcher matcher = compile.matcher(str);
- while(matcher.find()){
- System.out.println("matcher.group(0):"+matcher.group(0));
- System.out.println("分组一:matcher.group(1):"+matcher.group(1));
- System.out.println("分组二:matcher.group(2):"+matcher.group(2));
- System.out.println("分组名a1:matcher.group(1):"+matcher.group("a1"));
- System.out.println("分组名a2:matcher.group(2):"+matcher.group("a2"));
- }
- }
结果展示
结论:由此可见()除了能将正则分组,还能按顺序给出编号,从1开始。还可以给分组取名字,并根据名字获取对应匹配的值
非捕获分组
1)如20(?:20|21|22)表示匹配2020|2021|2022
- @Test
- public void test2(){
- String str = "2021a2022B2023";
- String regStr = "20(?:20|21|22)";
- Pattern compile = Pattern.compile(regStr);
- Matcher matcher = compile.matcher(str);
- while(matcher.find()){
- System.out.println("匹配到的数据为:"+matcher.group(0));
- }
- }
结果展示
2)如20(?=20|21|22)表示匹配2020或2021或2022中的20
- @Test
- public void test2(){
- String str = "2021a2022B2023";
- String regStr = "20(?=20|21|22)";
- Pattern compile = Pattern.compile(regStr);
- Matcher matcher = compile.matcher(str);
- while(matcher.find()){
- System.out.println("匹配到的数据为:"+matcher.group(0));
- }
- }
这里匹配到的20,为2021和2022中的20
3)如20(?!20|21|22)表示匹配不匹配2020或2021或2022中的20,匹配其它20
- @Test
- public void test2(){
- String str = "2021a2022B2023";
- String regStr = "20(?!20|21|22)";
- Pattern compile = Pattern.compile(regStr);
- Matcher matcher = compile.matcher(str);
- while(matcher.find()){
- System.out.println("匹配到的数据为:"+matcher.group(0));
- }
- }
这里匹配到的20为2023中的20
反向引用
-
字符串12345678870008,正则为(\\d)(\\d)\\2\\1
- @Test
- public void test2(){
- String str = "12345678870008";
-
- String regStr = "(\\d)(\\d)\\2\\1";
- Pattern compile = Pattern.compile(regStr);
- Matcher matcher = compile.matcher(str);
- while(matcher.find()){
- System.out.println("匹配到的数据为:"+matcher.group(0));
- }
- }
结果展示