{"id":27347,"date":"2022-12-23T21:37:41","date_gmt":"2022-12-23T16:07:41","guid":{"rendered":"https:\/\/jassweb.com\/solved\/solved-why-this-code-is-not-printing-30-since-int-is-primitive-and-mutable\/"},"modified":"2022-12-23T21:37:41","modified_gmt":"2022-12-23T16:07:41","slug":"solved-why-this-code-is-not-printing-30-since-int-is-primitive-and-mutable","status":"publish","type":"post","link":"https:\/\/jassweb.com\/solved\/solved-why-this-code-is-not-printing-30-since-int-is-primitive-and-mutable\/","title":{"rendered":"[Solved] Why this code is not printing 30, since int is primitive and mutable?"},"content":{"rendered":"<p> [ad_1]<br \/>\n<\/p>\n<div id=\"answer-28926895\" class=\"answer js-answer accepted-answer js-accepted-answer\" data-answerid=\"28926895\" data-parentid=\"28926874\" data-score=\"2\" 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<blockquote>\n<p>Why this code is not printing 30<\/p>\n<\/blockquote>\n<p>Because you&#8217;re outputting the <code>age<\/code> field of <code>person2<\/code>, which you never set to 30. You&#8217;re setting the <code>age<\/code> field of <strong><code>person1<\/code><\/strong> to <code>30<\/code>, but not <code>person2<\/code>. Instance fields are instance-specific.<\/p>\n<p>In particular, if you were expecting this line to create some link between the instances:<\/p>\n<pre><code>person2.setAge(person1.getAge());\n<\/code><\/pre>\n<p>it doesn&#8217;t. It gets the <em>value<\/em> of teh <code>age<\/code> field of <code>person1<\/code> and then assigns that <em>value<\/em> (<code>10<\/code>, at that point) to the <code>age<\/code> field of <code>person2<\/code>. There is no ongoing link between them.<\/p>\n<p>Blow-by-blow account:<\/p>\n<pre><code>Person person1 = new Person();        \/\/ Creates a Person instance\nperson1.setAge(10);                   \/\/ Sets person1's age to 10\n\nPerson person2 = new Person();        \/\/ Creates a separate Person instance\nperson2.setAge(person1.getAge());     \/\/ Sets person2's age to 10\n\nperson1.setAge(30);                   \/\/ Sets person1's age to 30; no effect on person2\n\nSystem.out.println(person2.getAge()); \/\/ Shows person2's age (10)\n<\/code><\/pre>\n<blockquote>\n<p>&#8230;since int is primitive and mutable?<\/p>\n<\/blockquote>\n<p><code>int<\/code> is primitive; you could argue that it&#8217;s <strong>not<\/strong> mutable, if you take mutable to mean what it normally means: Having state that can change. <code>int<\/code>s don&#8217;t have that. <code>5<\/code> is <code>5<\/code> is <code>5<\/code> and cannot change. Variables <em>containing<\/em> <code>int<\/code> values can be updated to contain <em>different<\/em> <code>int<\/code> values, but that&#8217;s changing the variable, not the <code>int<\/code>.<\/p>\n<p>In contrast, objects have state that can change without changing the variable that refers to them:<\/p>\n<pre><code>\/\/ Create a LinkedList and save a reference to it in `list`\nList&lt;String&gt; list = new LinkedList&lt;String&gt;();\n\n\/\/ Change the state of the list\nlist.add(\"Foo\");\n<\/code><\/pre>\n<p>In the second statement above, the <em>variable<\/em> <code>list<\/code> isn&#8217;t changed; it still contains a reference to the same list. That statement changes the state of the list (not the state of the variable referring to it).<\/p>\n<\/p><\/div>\n<div class=\"mt24\"><\/div>\n<\/div>\n<p>            <span class=\"d-none\" itemprop=\"commentCount\">6<\/span> <\/p><\/div>\n<\/div>\n<p>[ad_2]<\/p>\n<p>solved Why this code is not printing 30, since int is primitive and mutable? <\/p>\n","protected":false},"excerpt":{"rendered":"<p>[ad_1] Why this code is not printing 30 Because you&#8217;re outputting the age field of person2, which you never set to 30. You&#8217;re setting the age field of person1 to 30, but not person2. Instance fields are instance-specific. In particular, if you were expecting this line to create some link between the instances: person2.setAge(person1.getAge()); it &#8230; <a title=\"[Solved] Why this code is not printing 30, since int is primitive and mutable?\" class=\"read-more\" href=\"https:\/\/jassweb.com\/solved\/solved-why-this-code-is-not-printing-30-since-int-is-primitive-and-mutable\/\" aria-label=\"More on [Solved] Why this code is not printing 30, since int is primitive and mutable?\">Read more<\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[320],"tags":[323],"class_list":["post-27347","post","type-post","status-publish","format-standard","hentry","category-solved","tag-java"],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v27.4 - https:\/\/yoast.com\/product\/yoast-seo-wordpress\/ -->\n<title>[Solved] Why this code is not printing 30, since int is primitive and mutable? - 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-why-this-code-is-not-printing-30-since-int-is-primitive-and-mutable\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"[Solved] Why this code is not printing 30, since int is primitive and mutable? - JassWeb\" \/>\n<meta property=\"og:description\" content=\"[ad_1] Why this code is not printing 30 Because you&#8217;re outputting the age field of person2, which you never set to 30. You&#8217;re setting the age field of person1 to 30, but not person2. Instance fields are instance-specific. In particular, if you were expecting this line to create some link between the instances: person2.setAge(person1.getAge()); it ... 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