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#. Convert\nString[] to Stream

\n
Arrays.asList(new String[]{\"aa\", \"bb\"}).stream()
\n

int[] to Stream

\n\n
int[] arr = new int[]{1,3,5,7,9,2,4,6,8,1,3,5,7,9,2};\n\nint[] result = IntStream.of(arr)\n    .distinct().toArray();\n\nList<Integer> result = IntStream.of(arr)\n    .distinct().boxed()\n    .collect(Collectors.toList());
\n

to String[]

\n
Arrays.stream(new String[]{\"aaa\", \"abc\", \"ccc\", \"add\"})\n    .toArray(String[]::new);
\n

to int[]

\n
List<Integer> list = new ArrayList<>();\nlist.stream().mapToInt(i->i).toArray();
\n

List<List<Integer>> to int[][]

\n
List<List<Integer>> result;\nresult.stream()\n    .map(r -> r.stream().mapToInt(i -> i).toArray())\n    .toArray(int[][]::new);
\n

to Map

\n\n
Map<String, String> input = new HashMap<>() {{\n    put(\"string1\", \"41\");\n    put(\"string2\", \"42\");\n}};\n\nMap<String, String> collect = input.entrySet().stream()\n    .map(entry -> {\n        //  Map.Entry<String, String> newEntry = new AbstractMap.SimpleEntry(entry.getKey(), entry.getValue());\n        Map.Entry<String, String> newEntry = Map.entry(entry.getKey(), entry.getValue());\n        return newEntry;\n    })\n    .collect(Collectors.toMap(\n        entry -> entry.getKey(),\n        entry -> entry.getValue()\n    ));
\n\n
.collect(Collectors.toMap(\n    e -> e.getKey(),\n    e -> e.getValue(),\n    (x,y) -> y,\n    LinkedHashMap::new\n));
\n\n
public static <X, Y, Z> Map<X, Z> transform(Map<X, Y> input, Function<Y, Z> function) {\n    return input.entrySet().stream()\n      .collect(Collectors.toMap(\n           (entry) -> entry.getKey(),\n           (entry) -> function.apply(entry.getValue())\n      ))\n    ;\n}\n\nMap<String, String> input = new HashMap<String, String>() {{\n     put(\"string1\", \"41\");\n     put(\"string2\", \"42\");\n}};\nMap<String, Integer> output = transform(input, val -> Integer.parseInt(val));
\n
\n

#. Sort\nAES

\n
IntStream.of(14, 11, 20, 39, 23)\n    .sorted()\n    .boxed()\n    .collect(Collectors.toList());\n[11, 14, 20, 23, 39]
\n

DESC

\n
IntStream.of(14, 11, 20, 39, 23)\n    .sorted(Comparator.reverseOrder())\n    .boxed()\n    .collect(Collectors.toList());\n// [39, 23, 20, 14, 11]
\n

Custom

\n
Arrays.asList(new String[]{\"abce\", \"abcd\", \"cdx\"}).stream()\n    .sorted((string1, string2) -> {\n        int result = string1.charAt(n) - string2.charAt(n);\n        if(result == 0)\n            return string1.compareTo(string2);\n        return result;\n    })\n    .toArray(String[]::new);\n// input : [\"abce\", \"abcd\", \"cdx\"], n:2\n// output : [\"abcd\", \"abce\", \"cdx\"]
\n

문자열 정렬

\n\n
String targetStr = \"abcdefABC\";\nString result = targetStr.chars().mapToObj(String::valueOf)\n    .sorted(Collections.reverseOrder())\n    .collect(Collectors.joining());\n\n// StringBuilder 로 리턴\ntargetStr.chars().mapToObj(item -> (char)item)\n    .sorted(Comparator.reverseOrder())\n    .collect(StringBuilder::new, StringBuilder::appendCodePoint, StringBuilder::append)\n    .toString();
\n
\n

Grouping\n

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