{"id":207,"date":"2022-09-14T08:21:05","date_gmt":"2022-09-14T08:21:05","guid":{"rendered":"https:\/\/jassweb.com\/new22\/solved-regexp-for-matching-if-a-text-has-only-one-type-of-letter-example-kkkk\/"},"modified":"2022-09-14T08:21:05","modified_gmt":"2022-09-14T08:21:05","slug":"solved-regexp-for-matching-if-a-text-has-only-one-type-of-letter-example-kkkk-2","status":"publish","type":"post","link":"https:\/\/jassweb.com\/solved\/solved-regexp-for-matching-if-a-text-has-only-one-type-of-letter-example-kkkk-2\/","title":{"rendered":"[Solved] RegExp for matching if a text has only one type of letter, example \u201cKKKK\u201d"},"content":{"rendered":"<h2> Introduction <\/h2>\n<p>[ad_1]<\/p>\n<p>Regular expressions (RegEx) are a powerful tool for matching patterns in text. They can be used to check if a text contains only one type of letter, such as in the example &#8220;KKKK&#8221;. This can be done by creating a RegEx pattern that looks for any character that is repeated four times in a row. This pattern can then be used to test if a given text contains only one type of letter. In this article, we will discuss how to create a RegEx pattern for matching if a text has only one type of letter, and provide an example of how to use it.<\/p>\n<h2> Solution<\/h2>\n<p><\/p>\n<p>\/^(?:([a-zA-Z])\\1*)*$\/ <\/p>\n<p><\/p>\n<div class=\"entry-content\" itemprop=\"text\">\n<script async src=\"https:\/\/pagead2.googlesyndication.com\/pagead\/js\/adsbygoogle.js?client=ca-pub-1088640234840270\" crossorigin=\"anonymous\"><\/script><br \/>\n<script><\/p>\n<p><\/script><\/p>\n<p><\/p>\n<div id=\"answer-40089090\" class=\"answer js-answer accepted-answer js-accepted-answer\" data-answerid=\"40089090\" data-parentid=\"40088836\" data-score=\"0\" data-position-on-page=\"1\" data-highest-scored=\"1\" data-question-has-accepted-highest-score=\"1\" itemprop=\"acceptedAnswer\" itemscope itemtype=\"https:\/\/schema.org\/Answer\">\n<div class=\"post-layout\">\n<div class=\"votecell post-layout--left\"><\/div>\n<div class=\"answercell post-layout--right\">\n<div class=\"s-prose js-post-body\" itemprop=\"text\">\n<p>You can do this using groups and back-references.<\/p>\n<p>My examples are in Java\u2019s regex dialogue, but you can adapt it to any dialect that supports back-references. For example some engines need <code>\\(...\\)<\/code> instead of <code>(...)<\/code>.<\/p>\n<p>First you need a group, which you denote by surrounding in parentheses:<\/p>\n<pre><code>(.)\n<\/code><\/pre>\n<p>This matches any single character. If you want it to specifically be upper-case letters, you could use <code>(A-Z)<\/code> instead.<\/p>\n<p>Next you need to match a second character that is the same as the contents of the group. You can <em>back-reference<\/em> the contents of the first match using <code>\\1<\/code>:<\/p>\n<pre><code>(.)\\1\n<\/code><\/pre>\n<p>This will match <code>AA<\/code> or <code>BB<\/code> but not <code>AB<\/code>. And not <code>A<\/code>, since the second character is compulsory.<\/p>\n<p>Next you need to specify that the second character occurs any number of times, including zero. That\u2019s done with <code>*<\/code>.<\/p>\n<pre><code>(.)\\1*\n<\/code><\/pre>\n<p>This matches <code>A<\/code>, <code>B<\/code>, <code>AA<\/code>, <code>BB<\/code>, <code>AAA<\/code>, <code>BBBBBBB<\/code> but not <code>AB<\/code> or <code>AAB<\/code>.<\/p>\n<p>In Java, the <code>\\<\/code> has to be escaped:<\/p>\n<pre><code> Pattern pattern = Pattern.compile(\"(.)\\\\1*\");\n<\/code><\/pre>\n<p>Your regex engine might:<br \/>\n\u2013 use this to search the input string for a part that matches (so <code>BAAAAB<\/code> matches \u2014 it finds the <code>AAAA<\/code>)<br \/>\n\u2013 or it might require the whole string to match the pattern (so <code>BAAAAB<\/code> does not match).<\/p>\n<p>If you want the second behaviour from an engine that does the first, add <code>.*<\/code> either side of the pattern.<\/p>\n<p>If you want the first behaviour from an engine that does the second, add <code>^<\/code> at the start and <code>$<\/code> at the end of the pattern, these match the start and end of the line, respectively.<\/p>\n<\/div>\n<div class=\"mt24\"><\/div>\n<\/div>\n<p> <span class=\"d-none\" itemprop=\"commentCount\"><\/span> <\/p>\n<\/div>\n<\/div>\n<p>solved RegExp for matching if a text has only one type of letter, example \u201cKKKK\u201d <\/p>\n<p><script async src=\"https:\/\/pagead2.googlesyndication.com\/pagead\/js\/adsbygoogle.js?client=ca-pub-1088640234840270\" crossorigin=\"anonymous\"><\/script><br \/>\n<script><\/p>\n<p><\/script><\/div>\n<p>[ad_2]<\/p>\n<p>Regular expressions (RegEx) are a powerful tool for matching patterns in text. They can be used to check if a text contains only one type of letter, such as &#8220;KKKK&#8221;. To do this, you can use the following RegEx:<\/p>\n<pre><code>^([A-Za-z])\\1+$<\/code><\/pre>\n<p>This expression will match any string that contains only one type of letter. For example, it will match &#8220;KKKK&#8221; but not &#8220;KKKG&#8221;.<\/p>\n<p>The expression works by using a capturing group to match any letter (A-Z or a-z). The \\1+ part of the expression then checks that the same letter is repeated one or more times. The ^ and $ anchors ensure that the entire string is made up of the same letter.<\/p>\n<p>This expression can be used in a variety of programming languages, including JavaScript, Python, and PHP.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Introduction [ad_1] Regular expressions (RegEx) are a powerful tool for matching patterns in text. They can be used to check if a text contains only one type of letter, such as in the example &#8220;KKKK&#8221;. This can be done by creating a RegEx pattern that looks for any character that is repeated four times in &#8230; <a title=\"[Solved] RegExp for matching if a text has only one type of letter, example \u201cKKKK\u201d\" class=\"read-more\" href=\"https:\/\/jassweb.com\/solved\/solved-regexp-for-matching-if-a-text-has-only-one-type-of-letter-example-kkkk-2\/\" aria-label=\"More on [Solved] RegExp for matching if a text has only one type of letter, example \u201cKKKK\u201d\">Read more<\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[320],"tags":[347],"class_list":["post-207","post","type-post","status-publish","format-standard","hentry","category-solved","tag-regex"],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v26.5 - https:\/\/yoast.com\/wordpress\/plugins\/seo\/ -->\n<title>[Solved] RegExp for matching if a text has only one type of letter, example \u201cKKKK\u201d - JassWeb<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/jassweb.com\/solved\/solved-regexp-for-matching-if-a-text-has-only-one-type-of-letter-example-kkkk-2\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"[Solved] RegExp for matching if a text has only one type of letter, example \u201cKKKK\u201d - JassWeb\" \/>\n<meta property=\"og:description\" content=\"Introduction [ad_1] Regular expressions (RegEx) are a powerful tool for matching patterns in text. 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