{"id":328973,"date":"2023-09-29T06:15:31","date_gmt":"2023-09-29T06:15:31","guid":{"rendered":"https:\/\/www.baeldung.com\/?p=166218"},"modified":"2023-09-29T06:15:31","modified_gmt":"2023-09-29T06:15:31","slug":"check-if-a-list-contains-a-string-element-while-ignoring-case","status":"publish","type":"post","link":"https:\/\/itteacheritfreelance.hk\/wordpress\/index.php\/2023\/09\/29\/check-if-a-list-contains-a-string-element-while-ignoring-case\/","title":{"rendered":"Check if a List Contains a String Element While Ignoring Case"},"content":{"rendered":"

<\/p>\n

\"\"<\/p>\n

1. Overview<\/h2>\n
<\/div>\n

List<\/a><\/em> is a pretty commonly used data structure\u00a0in Java. Sometimes, we want to case-insensitively check if a string is an element in a string list.<\/p>\n

In this quick tutorial, we’ll explore various methods and strategies to solve this common problem in Java.<\/p>\n

2. Introduction to the Problem<\/h2>\n
<\/div>\n

List<\/em> provides the convenient contains()<\/em><\/a> method to check if a given value exists in the list. Under the hood, List.contains()<\/em> compares the given object with each element in the list through the equals()<\/em> method<\/strong>.<\/p>\n

Therefore, if the list is a List<String>,<\/em> the contains()<\/em> method only compares strings case-sensitively. For example, we have a list of movie titles:<\/p>\n

List<String> THE_LIST = List.of("Game of Thrones", "Forrest Gump", "American Beauty", "Pretty Woman", "Catch Me If You Can");<\/code><\/pre>\n
When we check whether it has “catch me if you can<\/em>” using the contains()<\/em> method, it returns\u00a0false:<\/em><\/p>\n
assertFalse(THE_LIST.contains("catch me if you can"));<\/code><\/pre>\n
However, in many cases, we want the contains()<\/em> method to support case-ignored checks. Unfortunately, the standard contains()<\/em> doesn’t offer us this option. So next, let’s see how to achieve our goal.<\/p>\n
For simplicity, we’ll leverage unit test assertions to verify whether each approach works as expected.<\/p>\n
3. Using a Loop<\/h2>\n
<\/div>\n
We know the String<\/em> class provides the equalsIgnoreCase()<\/em><\/a> method, which does case-insensitive equality checks. Therefore, the first idea to solve our problem is looping through the list and using the equalsIgnoreCase()<\/em> method to check each element and the given value:<\/strong><\/p>\n
boolean ignoreCaseContainsForLoop(List<String> list, String value) {\r\n    for (String e : list) {\r\n        if (value.equalsIgnoreCase(e)) {\r\n            return true;\r\n        }\r\n    }\r\n    return false;\r\n}<\/code><\/pre>\n
As the code above shows, we used a for<\/em>-loop<\/a> to check each element in the list. Once the equalsIgnoreCase()<\/em> method reports true<\/em> on an element, we return true<\/em> immediately and stop checking further<\/strong>. Otherwise, if no match is found among all the elements in the list, the method returns false.<\/em><\/p>\n
We can create a test to verify whether the ignoreCaseContainsForLoop()<\/em> method works as expected:<\/p>\n
assertTrue(ignoreCaseContainsForLoop(THE_LIST, "CATCH me if you CAN"));\r\nassertTrue(ignoreCaseContainsForLoop(THE_LIST, "game of thrones"));\r\nassertFalse(ignoreCaseContainsForLoop(THE_LIST, "The Godfather"));<\/code><\/pre>\n
4. Using the Stream API<\/h2>\n
<\/div>\n
Java introduced the Stream API<\/a> starting from version 8. The Stream API provides a powerful mechanism for efficiently and effectively processing collections.<\/p>\n
Next, let’s solve our problem using the Stream API:<\/p>\n
assertTrue(THE_LIST.stream().anyMatch(e -> e.equalsIgnoreCase("CATCH me if you CAN")));\r\n<\/code><\/pre>\n
As demonstrated, we utilized the anyMatch()<\/em> method from the Stream API to ascertain whether an element matches our criteria. We conveyed our criteria to anyMatch()<\/em> using a lambda expression.<\/strong><\/p>\n
Alternatively, we have the option to employ a method reference to pass the predicate to the anyMatch()<\/em> method:<\/strong><\/p>\n
assertTrue(THE_LIST.stream().anyMatch("game of thrones"::equalsIgnoreCase));\r\nassertFalse(THE_LIST.stream().anyMatch("The Godfather"::equalsIgnoreCase));<\/code><\/pre>\n
5. Conclusion<\/h2>\n
<\/div>\n
In this article, we’ve explored two approaches to performing a case-insensitive check to determine if a string list contains a specific string. <\/span><\/p>\n
First, we tackled the problem by crafting a traditional loop-based method. Next, we harnessed the power of the Stream API’s anyMatch()<\/em> method to accomplish the same objective.<\/span><\/p>\n
As always, the complete source code for the examples is available over on GitHub<\/span><\/a>.<\/span><\/p>\n
\"\"<\/p>\n
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<\/p>","protected":false},"excerpt":{"rendered":"
\"\"<\/p>\n
Explore two approaches to performing a case-insensitive check to determine if a string list contains a specific string.<\/p>\n
<\/a>\u00a0<\/a>\u00a0<\/a>\u00a0<\/a>\u00a0<\/a>\u00a0<\/a>\u00a0<\/a>\u00a0<\/div>\n<\/div>","protected":false},"author":915,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"slim_seo":{"title":"Check if a List Contains a String Element While Ignoring Case - ITTeacherITFreelance.hk","description":"Explore two approaches to performing a case-insensitive check to determine if a string list contains a specific string. \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0"},"footnotes":""},"categories":[6,1307],"tags":[10675],"_links":{"self":[{"href":"https:\/\/itteacheritfreelance.hk\/wordpress\/index.php\/wp-json\/wp\/v2\/posts\/328973"}],"collection":[{"href":"https:\/\/itteacheritfreelance.hk\/wordpress\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/itteacheritfreelance.hk\/wordpress\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/itteacheritfreelance.hk\/wordpress\/index.php\/wp-json\/wp\/v2\/users\/915"}],"replies":[{"embeddable":true,"href":"https:\/\/itteacheritfreelance.hk\/wordpress\/index.php\/wp-json\/wp\/v2\/comments?post=328973"}],"version-history":[{"count":1,"href":"https:\/\/itteacheritfreelance.hk\/wordpress\/index.php\/wp-json\/wp\/v2\/posts\/328973\/revisions"}],"predecessor-version":[{"id":328974,"href":"https:\/\/itteacheritfreelance.hk\/wordpress\/index.php\/wp-json\/wp\/v2\/posts\/328973\/revisions\/328974"}],"wp:attachment":[{"href":"https:\/\/itteacheritfreelance.hk\/wordpress\/index.php\/wp-json\/wp\/v2\/media?parent=328973"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/itteacheritfreelance.hk\/wordpress\/index.php\/wp-json\/wp\/v2\/categories?post=328973"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/itteacheritfreelance.hk\/wordpress\/index.php\/wp-json\/wp\/v2\/tags?post=328973"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}