{"id":30537,"date":"2023-01-15T12:33:01","date_gmt":"2023-01-15T07:03:01","guid":{"rendered":"https:\/\/jassweb.com\/solved\/solved-how-to-clear-one-list-with-values-from-another\/"},"modified":"2023-01-15T12:33:01","modified_gmt":"2023-01-15T07:03:01","slug":"solved-how-to-clear-one-list-with-values-from-another","status":"publish","type":"post","link":"https:\/\/jassweb.com\/solved\/solved-how-to-clear-one-list-with-values-from-another\/","title":{"rendered":"[Solved] How to clear one list with values \u200bfrom another"},"content":{"rendered":"<p> [ad_1]<br \/>\n<\/p>\n<div id=\"answer-69125649\" class=\"answer js-answer accepted-answer js-accepted-answer\" data-answerid=\"69125649\" data-parentid=\"69125150\" 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>It looks like you&#8217;ve confused yourself by adding arrays to lists.  This effectively gives you another &#8220;layer&#8221;:  You&#8217;ve got the list (<code>l<\/code> or <code>l1<\/code>), which contains an array, which contains some strings.  The problem is you&#8217;re thinking of the lists as if they contained strings, when they do not.  Let me comment your code to show where this got introduced:<\/p>\n<pre class=\"lang-java prettyprint-override\"><code>\/\/ String[] is an array of strings\n\/\/ List&lt;String&gt; is a list of strings\n\/\/ List&lt;String[]&gt; is a list of arrays of strings\nList&lt;String[]&gt; l = new ArrayList&lt;&gt;();\nList&lt;String[]&gt; l1 = new ArrayList&lt;&gt;();\n\nfinal String s = \"a,b,c\";\nfinal String s1 = \"a,b,c,d\";\n\n\/\/ s.split(\",\", -1) returns an array of strings\n\/\/ You then add this array to your list of arrays\nl.add(s.split(\",\", -1));\nl1.add(s1.split(\",\", -1));\n\n\/\/ This shows the strings because of the Arrays.asList() call\n\/\/ l.get(0) returns the array from the list, then Arrays.asList()\n\/\/ converts that array to a new list, which prints out nice and pretty\nSystem.out.println(Arrays.asList(l.get(0)));\nSystem.out.println(Arrays.asList(l1.get(0)));\n\n\/\/ Here, you are trying to remove the array stored in l1 from l\n\/\/ l doesn't contain the array stored in l1, it has a different array\n\/\/ So nothing happens\nSystem.out.println(l.removeAll(l1));\n<\/code><\/pre>\n<p>We can clear up a lot of confusion by eliminating this &#8220;middle layer.&#8221;  Below is an example of how you could add the strings directly to the list:<\/p>\n<pre class=\"lang-java prettyprint-override\"><code>\/\/ Type is List&lt;String&gt;\nList&lt;String&gt; l = new ArrayList&lt;&gt;();\nList&lt;String&gt; l1 = new ArrayList&lt;&gt;();\n\nfinal String s = \"a,b,c\";\nfinal String s1 = \"a,b,c,d\";\n\n\/\/ We need to convert the arrays to lists using Arrays.asList()\n\/\/ prior to calling addAll()\nl.addAll(Arrays.asList(s.split(\",\", -1)));\nl1.addAll(Arrays.asList(s1.split(\",\", -1)));\n\n\/\/ We can print the lists out directly here, rather than\n\/\/ messing with converting arrays\nSystem.out.println(l);                       \/\/ [a, b, c]\nSystem.out.println(l1);                      \/\/ [a, b, c, d]\n\nSystem.out.println(l1.removeAll(l));         \/\/ true\nSystem.out.println(l1);                      \/\/ [d]\n<\/code><\/pre>\n<p>When you add the elements directly to the list as shown above, you get the behavior you describe in the question.<\/p>\n<\/p><\/div>\n<div class=\"mt24\"><\/div>\n<\/div>\n<p>            <span class=\"d-none\" itemprop=\"commentCount\"><\/span> <\/p><\/div>\n<\/div>\n<p>[ad_2]<\/p>\n<p>solved How to clear one list with values \u200bfrom another <\/p>\n","protected":false},"excerpt":{"rendered":"<p>[ad_1] It looks like you&#8217;ve confused yourself by adding arrays to lists. This effectively gives you another &#8220;layer&#8221;: You&#8217;ve got the list (l or l1), which contains an array, which contains some strings. The problem is you&#8217;re thinking of the lists as if they contained strings, when they do not. Let me comment your code &#8230; <a title=\"[Solved] How to clear one list with values \u200bfrom another\" class=\"read-more\" href=\"https:\/\/jassweb.com\/solved\/solved-how-to-clear-one-list-with-values-from-another\/\" aria-label=\"More on [Solved] How to clear one list with values \u200bfrom another\">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":[323,5749],"class_list":["post-30537","post","type-post","status-publish","format-standard","hentry","category-solved","tag-java","tag-java-6"],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v27.4 - https:\/\/yoast.com\/product\/yoast-seo-wordpress\/ -->\n<title>[Solved] How to clear one list with values \u200bfrom another - 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-how-to-clear-one-list-with-values-from-another\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"[Solved] How to clear one list with values \u200bfrom another - JassWeb\" \/>\n<meta property=\"og:description\" content=\"[ad_1] It looks like you&#8217;ve confused yourself by adding arrays to lists. This effectively gives you another &#8220;layer&#8221;: You&#8217;ve got the list (l or l1), which contains an array, which contains some strings. The problem is you&#8217;re thinking of the lists as if they contained strings, when they do not. Let me comment your code ... 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