java regular expression summary

Regular expression with String

Regular expression replacement with String

• replaceAll // Replace all pairs

• replaceFirst // First replace

  /**

• Exclude non-alphabets.

• [^ a-zA-Z]-> Other than the alphabet */ private static void testReplace() { String str = "fjslru7974294jlsjfJLJL+;]:@:UOIUO"; String regex = "[^a-zA-Z]"; System.out.println(str.replaceAll(regex, "")); } //結果fjslrujlsjfJLJLUOIUO

Regular expression split by String

• split // split

  /**

• Divide the numbers by and make an array.

• [0-9] +-> Many numbers

• \ d +-> Many numbers */ private static void testSplit() { String str = "jfslj47924fjslk24729djldja492824"; String regex = "[0-9]+"; System.out.println(Arrays.toString(str.split(regex))); } // Result [jfslj, fjslk, djldja]

Regular expression matching by String

• matches // matching

• Decimal judgment

  /**

• \ d +-> Many numbers

  • \. -->.

• (\. \ d +)?-> 0 or 1 in parentheses

  */ private static void testMatchDouble() { String str = "10.5"; String regex = "\d+(\.\d+)?"; if(str.matches(regex)) { System.out.println(Double.parseDouble(str)); }else { System.out.println ("not double"); } }

• Date determination

  /**

• \ d {4}-> 4 numbers

• \ d {2}-> 2 numbers

  • \- -->- */ private static void testMatchDate() { String str = "2019-09-10"; String regex = "\d{4}\-\d{2}\-\d{2}"; if(str.matches(regex)) { try { System.out.println(new SimpleDateFormat("yyyy-MM-dd").parse(str)); } catch (ParseException e) { e.printStackTrace(); } }else { System.out.println ("not date"); } }

• Judgment of phone number

  /**

• \ d {10,12}-> 10-12 numbers

• \ d {3,5}-> 3-5 numbers

  • •        -->-
      

  */ private static void testMatchTellphoneNumber() { String str = "080-1111-1111"; String regex1 = "\d{10,12}"; String regex2 = "\d{3,5}-\d{3,5}-\d{3,5}"; if(str.matches(regex1) || str.matches(regex2)) { System.out.println(str); }else { System.out.println ("not phone number"); } }

• Email judgment

  /**

• \ w +-> Many alphabets

• [a-zA-Z]-> Many alphabets

  • @ -->@
  • \. -->.
  • \- -->-
  • \_ -->_

• [a-zA-Z0-9 \ _ \-\.]-> Alphabet or __. */ private static void testMatchEmail() { String str = "[email protected]_c-d.com"; String regex = "[a-zA-Z][a-zA-Z0-9\\-\.]{5,29}@[a-zA-Z0-9\\-\.]+\.\w+";

   if(str.matches(regex)) {
   	System.out.println(str);
   }else {
  

System.out.println ("not E-mail"); } }

Comparison of String regular expression and (Pattern, Matcher) regular expression

String and pattern

private static void textPattern() {

//文字列 String string = "da646dad4da64da54d6a4d5a4d6a4d5ae78w"; String regex = "[0-9]+"; // Divide by pattern Pattern pattern = Pattern.compile(regex); System.out.println(Arrays.toString(pattern.split(string))); // Divide by string System.out.println(Arrays.toString(string.split(regex))); } // Result [da, dad, da, da, d, a, d, a, d, a, d, ae, w] 　　　[da, dad, da, da, d, a, d, a, d, a, d, ae, w]

String and matcher

private static void testMatcher() {
	String str = "2019-09-10";
	String regex = "\\d{4}\\-\\d{2}\\-\\d{2}";

// Matching by Matcher Pattern pattern = Pattern.compile(regex); Matcher matcher = pattern.matcher(str); System.out.println(""+ matcher.matches()); // Matching by String System.out.println(""+str.matches(regex)); } // Result true true

Summary of frequently used regular expressions

One letter

Many characters

Numerous judgments

Sample code