{"id":12001,"date":"2022-09-29T06:50:23","date_gmt":"2022-09-29T01:20:23","guid":{"rendered":"https:\/\/jassweb.com\/solved\/solved-create-a-map-with-values-of-one-map-as-key-and-values-of-each-map-as-values-from-a-list-of-maps-closed\/"},"modified":"2022-09-29T06:50:23","modified_gmt":"2022-09-29T01:20:23","slug":"solved-create-a-map-with-values-of-one-map-as-key-and-values-of-each-map-as-values-from-a-list-of-maps-closed","status":"publish","type":"post","link":"https:\/\/jassweb.com\/solved\/solved-create-a-map-with-values-of-one-map-as-key-and-values-of-each-map-as-values-from-a-list-of-maps-closed\/","title":{"rendered":"[Solved] Create a map with values of one map as key and values of each map as values from a list of maps [closed]"},"content":{"rendered":"<p> [ad_1]<br \/>\n<\/p>\n<div id=\"answer-69827050\" class=\"answer js-answer accepted-answer js-accepted-answer\" data-answerid=\"69827050\" data-parentid=\"69826629\" data-score=\"4\" 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 want something like this:<\/p>\n<pre><code>List&lt;Map&lt;String, String&gt;&gt; result = four.stream()  \/\/ iterate the Map with values\n   .map(map -&gt; map.entrySet()                     \/\/ .. for each one\n           .stream()                              \/\/ .. stream and collect\n           .collect(Collectors.toMap(             \/\/ .. into a new Map\n                   e -&gt; one.get(e.getKey()),      \/\/ .. with a key from the `one` Map\n                   Map.Entry::getValue)))         \/\/ .. and the same value\n   .collect(Collectors.toList());                 \/\/ and pack as a List\n<\/code><\/pre>\n<p>The output on calling <code>result.forEach(System.out::println);<\/code> is (remember that <code>HashMap<\/code> is unordered):<\/p>\n<pre><code>{Engineer=Software Engineer, Doctor=MBBS}\n{Engineer=Aerospace Engineer, Doctor=Ortho}\n<\/code><\/pre>\n<p>If you want the keys in each map sorted, you need to use the <code>TreeMap<\/code> implementation and an overloaded <a rel=\"nofollow noopener\" target=\"_blank\" href=\"https:\/\/docs.oracle.com\/javase\/8\/docs\/api\/java\/util\/stream\/Collectors.html#toMap-java.util.function.Function-java.util.function.Function-java.util.function.BinaryOperator-java.util.function.Supplier-\"><code>Collectors.toMap(Function, Function, BinaryOperator, Supplier)<\/code><\/a>. However, the default behavior of the merger <code>BinaryOperator<\/code> in the previous <a rel=\"nofollow noopener\" target=\"_blank\" href=\"https:\/\/docs.oracle.com\/javase\/8\/docs\/api\/java\/util\/stream\/Collectors.html#toMap-java.util.function.Function-java.util.function.Function-\"><code>Collectors.toMap(Function, Function)<\/code><\/a> method is that it throws an exception on duplicated keys. You have to implement this one by yourself.<\/p>\n<pre><code>BinaryOperator&lt;String&gt; throwingMerger = (u,v) -&gt; { \n            throw new IllegalStateException(String.format(\"Duplicate key %s\", u)); \n};\n        \nList&lt;Map&lt;String, String&gt;&gt; result = four.stream() \/\/ iterate the Map with values\n    .map(map -&gt; map.entrySet()                     \/\/ .. for each one\n            .stream()                              \/\/ .. stream and collect\n            .collect(Collectors.toMap(             \/\/ .. into a new Map\n                    e -&gt; one.get(e.getKey()),      \/\/ .. with a key from the `one` Map\n                    Map.Entry::getValue,           \/\/ .. and the same value\n                    throwingMerger,                \/\/ .. failing fast on duplicated keys\n                    TreeMap::new)))                \/\/ .. as TreeMap\n    .collect(Collectors.toList());                 \/\/ and pack as a List\n<\/code><\/pre>\n<pre><code>{Doctor=MBBS, Engineer=Software Engineer}\n{Doctor=Ortho, Engineer=Aerospace Engineer}\n<\/code><\/pre>\n<\/p><\/div>\n<div class=\"mt24\"><\/div>\n<\/div>\n<p>            <span class=\"d-none\" itemprop=\"commentCount\">5<\/span> <\/p><\/div>\n<\/div>\n<p>[ad_2]<\/p>\n<p>solved Create a map with values of one map as key and values of each map as values from a list of maps [closed] <\/p>\n","protected":false},"excerpt":{"rendered":"<p>[ad_1] You want something like this: List&lt;Map&lt;String, String&gt;&gt; result = four.stream() \/\/ iterate the Map with values .map(map -&gt; map.entrySet() \/\/ .. for each one .stream() \/\/ .. stream and collect .collect(Collectors.toMap( \/\/ .. into a new Map e -&gt; one.get(e.getKey()), \/\/ .. with a key from the `one` Map Map.Entry::getValue))) \/\/ .. and the &#8230; <a title=\"[Solved] Create a map with values of one map as key and values of each map as values from a list of maps [closed]\" class=\"read-more\" href=\"https:\/\/jassweb.com\/solved\/solved-create-a-map-with-values-of-one-map-as-key-and-values-of-each-map-as-values-from-a-list-of-maps-closed\/\" aria-label=\"More on [Solved] Create a map with values of one map as key and values of each map as values from a list of maps [closed]\">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":[1616,323],"class_list":["post-12001","post","type-post","status-publish","format-standard","hentry","category-solved","tag-collections","tag-java"],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v26.5 - https:\/\/yoast.com\/wordpress\/plugins\/seo\/ -->\n<title>[Solved] Create a map with values of one map as key and values of each map as values from a list of maps [closed] - 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-create-a-map-with-values-of-one-map-as-key-and-values-of-each-map-as-values-from-a-list-of-maps-closed\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"[Solved] Create a map with values of one map as key and values of each map as values from a list of maps [closed] - JassWeb\" \/>\n<meta property=\"og:description\" content=\"[ad_1] You want something like this: List&lt;Map&lt;String, String&gt;&gt; result = four.stream() \/\/ iterate the Map with values .map(map -&gt; map.entrySet() \/\/ .. for each one .stream() \/\/ .. stream and collect .collect(Collectors.toMap( \/\/ .. into a new Map e -&gt; one.get(e.getKey()), \/\/ .. with a key from the `one` Map Map.Entry::getValue))) \/\/ .. and the ... 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