正则表达式是修改java先前存在的正则表达式以允许一个新字符的最佳方法

Question

有一个预先存在的正则表达式，在一个条件下，它应该允许多个字符：

String regex = "^[a-zA-Z0-9\u00A0-\uD7FF\uF900-\uFDCF\uFDF0-\uFFEF \\-&*()_+|~=`{}\\[\\]:\";'<>?,.]{0,900}$";

if (condition is true) { 
      regex = regex .substring(0, 47) + "/" + regex.substring(47, 
      regex.length());
}

Answer 1

您可以使用charclass并集：

String myCharclass = "[a-zA-Z0-9\u00A0-\uD7FF\uF900-\uFDCF\uFDF0-\uFFEF \\-&*()_+|~=`{}\\[\\]:\";'<>?,.]"

if (condition)
    myCharclass = "[/" + charclass + "]"; // a character class union

String regex = "^" + myCharclass + "{0,900}$";

如果使用almson-regex编写，它将如下所示：

import static net.almson.util.Regex.*;

String myCharclass = charclassUnion (LETTER, DIGIT, charclassRange ('\u00A0', '\uD7FF'), charclassRange ('\uF900', '\uFDCF'), charclassRange ('\uFDF0','\uFFEF'), charclass (' ', '-', '&', '*', '(', ')', '_', '+', '|', '~', '=', '`', '{', '}', '[', ']', ':', '"', ';', '\'', '<', '>', '?', ',', '.'));

if (condition)
    myCharclass = charclassUnion (myCharclass, charclass ('/'));

regex = START_BOUNDARY + between (0, 900, myCharclass) + END_BOUNDARY;

Answer 2

最好的方法可能是分别定义它们，然后根据您的if条件使用它们

    String regex1 = "^[a-zA-Z0-9\u00A0-\uD7FF\uF900-\uFDCF\uFDF0-\uFFEF \\-&*()_+|~=`{}\\[\\]:\";'<>?,.]{0,900}$";
    String regex2 = "^[a-zA-Z0-9\u00A0-\uD7FF\uF900-\uFDCF\uFDF0-\uFFEF \\-&*()_+|~=`{}\\[\\]:\";'<>?,/.]{0,900}$";

    String currentRegex;
    if (condition is true) { 
          currentRegex = regex2;
    } else {
        currentRegex = regex1;
    }