정규표현식) 메타문자 ^ . [] 써보기

정규표현식 써보기

 

 

[] 안에서의 ^

해당 문자를 제외한 문자 중 하나와 일치

 

public class Main {
    public static void main(String[] args) {
        String num = "123854-4565156";
        num = num.replaceAll("[^-]", "*");
        System.out.println(num);
    }
}

[] 안의 "-"를 제외한 문자들이 모두 "*"로 변환되었다.

 

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^

[]밖에서는 문자열의 시작 부분을 나타낸다.

public class Main {
    public static void main(String[] args) {
        String str1 = "abcde";
        String str2 = "bcde";
        String str3 = "apple";

        boolean matches1 = str1.matches("^a....");
        System.out.println("str1 : " + str1);
        System.out.println("regex : ^a....");
        System.out.println("result: " + matches1);
        System.out.println();

        boolean matches2 = str2.matches("^b[a-z][a-z][a-z]");
        System.out.println("str2 : " + str2);
        System.out.println("regex : ^b[a-z][a-z][a-z]");
        System.out.println("result: " + matches2);
        System.out.println();

        boolean matches3 = str3.matches("[a-z]^[p][p][l][e]");
        System.out.println("str3 : " + str3);
        System.out.println("regex : [a-z]^[p][p][l][e]");
        System.out.println("result: " + matches3);
        System.out.println();

        boolean matches4 = str3.matches("^[a-z][p][p][l][e]");
        System.out.println("str3 : " + str3);
        System.out.println("regex : ^[a-z][p][p][l][e]");
        System.out.println("result: " + matches4);
        System.out.println();
        
    }
}

'^'뒤에 문자로 시작하는 문자라는 의미

 

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.

임의의 문자 하나를 나타낸다. 단, 줄 바꿈 문자(\n)는 제외

public class Main {
    public static void main(String[] args) {
        String str1 = "abc";
        String str2 = "adc";
        String str3 = "aec";
        String str4 = "ac";
        String str5 = "abbc";
        String str6 = "accc";
        String str7 = "adec";
        String str8 ="a\nc";

        boolean matches1 = str1.matches("a.c");
        System.out.println("str1 : " + str1);
        System.out.println("matches1 : " + matches1);

        boolean matches2 = str2.matches("a.c");
        System.out.println("str2 : " + str2);
        System.out.println("matches2 : " + matches2);

        boolean matches3 = str3.matches("a.c");
        System.out.println("str3 : " + str3);
        System.out.println("matches3 : " + matches3);

        boolean matches4 = str4.matches("a.c");
        System.out.println("str4 : " + str4);
        System.out.println("matches4 : " + matches4);

        boolean matches5 = str5.matches("a.c");
        System.out.println("str5 : " + str5);
        System.out.println("matches5 : " + matches5);

        boolean matches6 = str6.matches("a.c");
        System.out.println("str6 : " + str6);
        System.out.println("matches6 : " + matches6);

        boolean matches7 = str7.matches("a..c");
        System.out.println("str7 : " + str7);
        System.out.println("matches7 : "+ matches7);

        boolean matches8 = str8.matches("a.c");
        System.out.println("str8 : " + str8);
        System.out.println("matches8 : "+ matches8);
    }
}

 

---

[]

대괄호 안에 들어가는 문자 중 하나와 일치하는지

 

public class Main {
    public static void main(String[] args) {
        String str1 = "d";
        String str2 = "ad";
        String str3 = "apple";
        String str4 = "[";
        String str5 = "[apple]";
        
        boolean matches = str1.matches("[acd]");
        System.out.println("str1 : " + str1);
        System.out.println("regex : [acd]");
        System.out.println("result : " + matches);
        System.out.println();

        boolean matches2 = str2.matches("[a-c][b-d]");
        System.out.println("str2 : " + str2);
        System.out.println("regex : [a-c][b-d]");
        System.out.println("result : " + matches2);
        System.out.println();

        boolean matches3 = str3.matches("[a][p][p][l][e]");
        System.out.println("str3 : " + str3);
        System.out.println("regex : [a][p][p][l][e]");
        System.out.println("result : " + matches3);
        System.out.println();

        boolean matches4 = str3.matches("[apple]");
        System.out.println("str3 : " + str3);
        System.out.println("regex : [apple]");
        System.out.println("result : " + matches4);
        System.out.println();

        boolean matches5 = str4.matches("[\\[]");
        System.out.println("str4 : " + str4);
        System.out.println("regex : [\\[]");
        System.out.println("result : " + matches5);
        System.out.println();

        boolean matches6 = str5.matches("[\\[][a][p][p][a-z][a-z].");
        System.out.println("str5 : " + str5);
        System.out.println("regex : [\\[][a][p][p][a-z][a-z].");
        System.out.println("result : " + matches6);
        System.out.println();

    }
}

 

대괄호를 써보며 false만 맞닥 뜨리다가

이것저것 넣어보며 이제는 정확하게 이해하게 되었다.

 

matches() 메서드의 괄호 안의 값과 정확하게 일치가 되어야

true를 반환한다.