{"id":22713,"date":"2025-05-02T07:52:34","date_gmt":"2025-05-02T05:52:34","guid":{"rendered":"http:\/\/blog.wenzlaff.de\/?p=22713"},"modified":"2025-05-02T19:45:25","modified_gmt":"2025-05-02T17:45:25","slug":"record-patterns-2","status":"publish","type":"post","link":"http:\/\/blog.wenzlaff.de\/?p=22713","title":{"rendered":"Record Patterns: Wie Record Patterns das Extrahieren von Komponenten vereinfachen (2)"},"content":{"rendered":"<p><img loading=\"lazy\" decoding=\"async\" src=\"http:\/\/blog.wenzlaff.de\/wp-content\/uploads\/2025\/05\/records.jpg\" alt=\"\" width=\"1920\" height=\"1080\" class=\"aligncenter size-full wp-image-22710\" srcset=\"http:\/\/blog.wenzlaff.de\/wp-content\/uploads\/2025\/05\/records.jpg 1920w, http:\/\/blog.wenzlaff.de\/wp-content\/uploads\/2025\/05\/records-300x169.jpg 300w, http:\/\/blog.wenzlaff.de\/wp-content\/uploads\/2025\/05\/records-1024x576.jpg 1024w, http:\/\/blog.wenzlaff.de\/wp-content\/uploads\/2025\/05\/records-768x432.jpg 768w, http:\/\/blog.wenzlaff.de\/wp-content\/uploads\/2025\/05\/records-1536x864.jpg 1536w\" sizes=\"auto, (max-width: 767px) 89vw, (max-width: 1000px) 54vw, (max-width: 1071px) 543px, 580px\" \/><\/p>\n<p><!--more--><\/p>\n<pre class=\"lang:java decode:true \" >\r\n\r\npackage de.wenzlaff.twrente;\r\n\r\nimport java.math.BigDecimal;\r\n\r\n\/**\r\n * Verwendung von Record Patterns beim Pattern Matching.\r\n * \r\n * Mit JEP 440 in Java 21 eingef\u00fchrt\r\n *  \r\n * @author Thomas Wenzlaff\r\n *\/\r\npublic class StartJava21 {\r\n\r\n\t\/\/ Records sind Klassen mit einer neuen kompakten Schreibweise zum Halten von unver\u00e4nderlichen Daten.\r\n\t\/\/ K\u00f6nnen \u00fcbrigens mittels Jackson direkt geparst und gleichzeitig per Annotation validiert werden.\r\n\t\/\/ Instanziert wird ein neuer Record immer mit dem Konstruktor, der alle Argumente enth\u00e4lt. \r\n\t\/\/ Dieser Konstruktor ergibt sich bereits aus der Record Definition.\r\n\trecord Point(int x, int y) {}\r\n\t\r\n\trecord Info(String thema) {}\r\n\t\r\n\trecord Mindmap(String name, Long id, String thema) {};\r\n\r\n\trecord ParameterObjekt(int id, BigDecimal w\u00e4hrung, Long ziel) { \r\n\t\t\/\/ default Konstruktor f\u00fcr w\u00e4hrung und ziel\r\n\t\tpublic ParameterObjekt(int id) { \r\n\t\tthis(id,BigDecimal.TEN, Long.MIN_VALUE); \r\n\t}};\r\n\t\r\n\tpublic static void main(String[] args) {\r\n\t\t\r\n\t\tObject obj = new Point(3, 4);\r\n\t\t\r\n\t\tif (obj instanceof Point(int x, int y)) {\r\n\t\t    System.out.println(\"x=\" + x + \", y=\" + y + \" Summe=\" + (x + y));\r\n\t\t    \/\/ Achtung, ohne Klammern:\r\n\t\t    System.out.println(\"x=\" + x + \", y=\" + y + \" Summe=\" + x + y); \/\/ = 34 !\r\n\t\t}\r\n\t\t\r\n\t\t\/\/ erzeugt automatisch:\r\n\t\t\/\/ Getter Methoden ...\r\n\t\t\/\/ equals Methode ...\r\n\t\t\/\/ hashCode Methode ...\r\n\t\t\/\/ toString Methode ...\r\n\t\t\r\n\t\tInfo i = new Info(\"Attributnamen ohne get also i.thema statt i.getThema\");\r\n\t\tSystem.out.println(\"Info: \" + i.thema + \" und toString: \" + i.toString()); \/\/ Info[thema=Attributnamen ohne get also i.thema statt i.getThema]\r\n\t\tSystem.out.println(\"hashCode: \" + i.hashCode()); \/\/ -702758727\r\n\t\tSystem.out.println(\"equals: \" + i.equals(i)); \/\/ true\r\n\t\t\r\n\t\tSystem.out.println(\"equals Info - Point: \" + i.equals(obj)); \/\/ false\r\n\t\t\r\n\t\tSystem.err.println(\"Keine setThema, da nicht ver\u00e4nderbar\");\r\n\t\t\r\n\t\tParameterObjekt btc = new ParameterObjekt(5, BigDecimal.ONE, Long.MAX_VALUE);\r\n\t\tSystem.out.println(\"Betrag: \" + btc.w\u00e4hrung); \/\/ 1\r\n\t\t\r\n\t\tParameterObjekt btcDefault = new ParameterObjekt(2);\r\n\t\tSystem.out.println(\"Default Betrag: \" + btcDefault.w\u00e4hrung); \/\/ 10\t\t\r\n\t}\r\n}\r\n<\/pre>\n","protected":false},"excerpt":{"rendered":"","protected":false},"author":2,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_import_markdown_pro_load_document_selector":0,"_import_markdown_pro_submit_text_textarea":"","footnotes":""},"categories":[220,6201,6202],"tags":[2178,6196,6198,6200],"class_list":["post-22713","post","type-post","status-publish","format-standard","hentry","category-anleitung","category-challenge","category-java-21-challenge","tag-java","tag-records","tag-records-tag","tag-recordschallenge"],"_links":{"self":[{"href":"http:\/\/blog.wenzlaff.de\/index.php?rest_route=\/wp\/v2\/posts\/22713","targetHints":{"allow":["GET"]}}],"collection":[{"href":"http:\/\/blog.wenzlaff.de\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/blog.wenzlaff.de\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/blog.wenzlaff.de\/index.php?rest_route=\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"http:\/\/blog.wenzlaff.de\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=22713"}],"version-history":[{"count":0,"href":"http:\/\/blog.wenzlaff.de\/index.php?rest_route=\/wp\/v2\/posts\/22713\/revisions"}],"wp:attachment":[{"href":"http:\/\/blog.wenzlaff.de\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=22713"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/blog.wenzlaff.de\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=22713"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/blog.wenzlaff.de\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=22713"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}