@@ -106,27 +106,25 @@ all(x % 2 == 0 for x in number_list)
106106** Java declaration/methods**
107107
108108``` java
109- var arr = new int []{1 , 2 , 3 , 4 , 5 };
109+ int [] arr = new int []{1 , 2 , 3 , 4 , 5 }; // array
110+ int [][] matrix = new int [m][n]; // 2d array (m by n matrix)
111+ ```
110112
111- // 2d array (m by n matrix)
112- var matrix = new int [m][n] ;
113+ ``` java
114+ import java.util.* ;
113115
114116// Arrays
115- import java.util.Arrays ;
116117binarySearch(arr, 3 ), equals(arr, another_arr), copyOf(arr, arr. length), copyOfRange(arr, from, to),
117118sort(arr), sort(arr, from, to), fill(arr, 42 ), fill(arr, from, to, 42 ),
118119// Arrays.stream()
119120anyMatch(x - > x % 2 == 0 ), allMatch(x - > x % 2 == 0 ), noneMatch(x - > x % 2 == 0 ),
120121count(), sum(), min(), max(), average(), map(x - > x * 2 ). toArray(), filter(x - > x % 2 == 0 ). count()
121122
122123// Collections
123- import java.util.Collections ;
124124sort(list), binarySearch(list, 3 ), min(list), max(list), swap(list, 0 , 1 ), replaceAll(list, 1 , 2 ),
125125frequency(list, 1 ), reverse(list), rotate(list, 1 ), shuffle(list), unmodifiableList(list)
126126
127127// list
128- import java.util.Comparator ;
129- import java.util.List ;
130128var list = Arrays . asList(boxedArray);
131129Arrays . stream(arr). boxed(). collect(Collectors . toList())
132130sort(), sort(Comparator . naturalOrder()), sort(Comparator . reverseOrder())
@@ -138,14 +136,14 @@ str.toCharArray() // string to char array
138136str. chars(). toArray() // string to int array
139137
140138// boxing
141- var v = Arrays . stream(arr). boxed(). toArray(Integer []:: new ); // int[] to Integer[]
142- var v = Arrays . stream(arr). mapToObj(String :: valueOf). toArray(String []:: new ); // int[] to String[]
143- var v = Arrays . stream(arr). boxed(). collect(Collectors . toList()); // int[] to List<Integer>
139+ var arr1 = Arrays . stream(arr). boxed(). toArray(Integer []:: new ); // int[] to Integer[]
140+ var arr2 = Arrays . stream(arr). mapToObj(String :: valueOf). toArray(String []:: new ); // int[] to String[]
141+ var arr3 = Arrays . stream(arr). boxed(). collect(Collectors . toList()); // int[] to List<Integer>
144142
145143// integer sequence
146- var arr = IntStream . range(0 , speeds . length ). toArray(); // range to int array in [0, n)
147- var arr = IntStream . rangeClosed(1 , speeds . length ). toArray(); // range to int array in [1, n]
148- var list = IntStream . range(0 , speeds . length ). boxed(). collect( Collectors . toList() ); // range to list
144+ var arr = IntStream . range(0 , n ). toArray(); // range to int array in [0, n)
145+ var arr = IntStream . rangeClosed(1 , n ). toArray(); // range to int array in [1, n]
146+ var list = IntStream . range(0 , n ). boxed(). toList(); // range to list
149147
150148var list = List . of(arr); // array to list
151149var list = Arrays . asList(arr); // array to list
@@ -438,29 +436,26 @@ sample_counter.update([1, 1, 2, 2, 3])
438436** Java declaration/ methods**
439437
440438```java
439+ import java. util. * ;
440+
441441// map
442- import java.util. HashMap ;
443- var map = new HashMap<String , Integer > ();
442+ Map<String , Integer > map = new HashMap<> ();
444443put(" a" , 1 ), putIfAbsent(" b" , 2 ), get(" a" ), getOrDefault(" f" , 6 ), remove(" a" ), size(), isEmpty(),
445444keySet(), values(), entrySet(), containsKey(" a" ), containsValue(1 ), replace(" a" , 2 ), clear()
446445var keys = map. keySet(). toArray(String []:: new );
447446var values = map. values(). toArray(Integer []:: new );
448447
449448// set
450- import java.util. HashSet ;
451- var set = new HashSet<Integer > ();
449+ Set<Integer > set = new HashSet<> ();
452450add(1 ), remove(1 ), size(), isEmpty(), contains(1 ), clear(), iterator()
453451var arr = set. toArray(Integer []:: new );
454452
455453// enum map
456- import java.util. EnumMap ;
457454Map<City , Integer > map = new EnumMap<> (City . class);
458455
459456// linked hash map, linked hash set
460- import java.util. LinkedHashMap ;
461- import java.util. LinkedHashSet ;
462- var map = new LinkedHashMap<String , Integer > ();
463- var set = new LinkedHashSet<Integer > ();
457+ Map<String , Integer > map = new LinkedHashMap<> ();
458+ Set<Integer > set = new LinkedHashSet<> ();
464459
465460// unboxing
466461int [] result = map. entrySet(). stream()
@@ -478,15 +473,13 @@ Map<String, Integer> map = Maps.newLinkedHashMap();
478473Set<Integer > set = Sets . newLinkedHashSet();
479474
480475// guava multiset (implements Multiset<E>)
481- import com. google. common. collect. * ;
482476Multiset<String > multiset = HashMultiset . create();
483477Multiset<String > multiset = TreeMultiset . create();
484478Multiset<String > multiset = LinkedHashMultiset . create();
485479Multiset<String > multiset = ConcurrentHashMultiset . create();
486480Multiset<String > multiset = ImmutableMultiset . of(" a" , " b" , " c" );
487481
488482// guava multimap (implements Multimap<K, V>)
489- import com. google. common. collect. * ;
490483Multimap<String , Integer > multimap = ArrayListMultimap . create();
491484Multimap<String , Integer > multimap = HashMultimap . create();
492485Multimap<String , Integer > multimap = LinkedListMultimap . create();
@@ -496,14 +489,12 @@ Multimap<String, Integer> multimap = ImmutableListMultimap.of("a", 1, "a", 2, "b
496489Multimap<String , Integer > multimap = ImmutableSetMultimap . of(" a" , 1 , " a" , 2 , " b" , 3 );
497490
498491// guava bimap (implements BiMap<K, V>, Map<K, V>)
499- import com. google. common. collect. * ;
500492BiMap<String , Integer > bimap = HashBiMap . create();
501493BiMap<String , Integer > bimap = ImmutableBiMap . of(" a" , 1 , " b" , 2 );
502494BiMap<City , Country > bimap = EnumBiMap . create(City . class, Country . class);
503495BiMap<City , Integer > bimap = EnumHashBiMap . create(City . class);
504496
505497// guava table (implements Table<R, C, V>)
506- import com. google. common. collect. * ;
507498Table<Vertex , Vertex , Double > weightedGraph = HashBasedTable . create();
508499Table<Vertex , Vertex , Double > weightedGraph = TreeBasedTable . create();
509500Table<Vertex , Vertex , Double > weightedGraph = ArrayTable . create(Arrays . asList(v1, v2), Arrays . asList(v3, v4));
@@ -549,9 +540,9 @@ heapq.heappush(number_list, 6), heapq.heappop(number_list), heapq.heapreplace(nu
549540** Java declaration/ methods**
550541
551542```java
552- import java.util. PriorityQueue ;
553- var queue = new PriorityQueue<Integer > ();
554- var queue = new PriorityQueue<Integer > (Collections . reverseOrder());
543+ import java. util. * ;
544+ Queue< Integer > queue = new PriorityQueue<> ();
545+ Queue< Integer > queue = new PriorityQueue<> (Collections . reverseOrder());
555546add(1 ), peek(), poll(), remove(), size(), isEmpty(),
556547contains(1 ), clear(), iterator()
557548
@@ -592,17 +583,17 @@ push_front(4), emplace_front(5), pop_front(), reverse(), sort()
592583** Java declaration/ methods**
593584
594585```java
586+ import java. util. * ;
587+
595588// doubly linked list
596- import java.util. LinkedList ;
597- var list = new LinkedList<Integer > ();
589+ List<Integer > list = new LinkedList<> ();
598590add(1 ), addAll(List . of(2 , 3 , 4 , 5 )),
599591remove(0 ), removeFirst(), removeLast(), removeIf(x - > x % 2 == 0 ), subList(1 , 3 ),
600592get(0 ), getFirst(), getLast(), size(), isEmpty(), contains(1 ), containsAll(List . of(1 , 2 , 3 )),
601593iterator(), listIterator()
602594
603595// dynamically resized array
604- import java.util. ArrayList ;
605- var list = new ArrayList<Integer > ();
596+ List<Integer > list = new ArrayList<> ();
606597add(1 ), addAll(List . of(2 , 3 , 4 , 5 )), remove(0 ), subList(1 , 3 ),
607598get(0 ), size(), isEmpty(), contains(3 ), containsAll(List . of(3 , 4 )),
608599iterator(), listIterator()
@@ -657,8 +648,8 @@ append(6), appendleft(7), pop(), popleft()
657648** Java declaration/ methods**
658649
659650```java
660- import java.util. ArrayDeque ;
661- var deque = new ArrayDeque<Integer > ();
651+ import java. util. * ;
652+ Deque< Integer > deque = new ArrayDeque<> ();
662653add(1 ), remove(), pop(), size(), isEmpty(), contains(1 ), clear(),
663654offerFirst(6 ), offerLast(7 ), pollFirst(), pollLast(), peekFirst(), peekLast(),
664655addFirst(8 ), addLast(9 ), removeFirst(), removeLast(), getFirst(), getLast(),
@@ -699,8 +690,8 @@ append(4), pop()
699690** Java declaration/ methods**
700691
701692```java
702- import java.util. Stack ;
703- var stack = new Stack<Integer > ();
693+ import java. util. * ;
694+ Stack< Integer > stack = new Stack<> ();
704695push(1 ), add(1 , 2 ), addAll(anotherList), pop(), peek(), size(), isEmpty(),
705696contains(1 ), search(1 ), size(),
706697remove(1 ), removeIf(x - > x == 1 ), clear(),
@@ -746,21 +737,21 @@ sort_dict = SortedDict({'a': 1, 'b': 2, 'c': 3, 'd': 4, 'e': 5})
746737** Java declaration/ methods (binary search tree based)**
747738
748739```java
740+ import java. util. * ;
741+
749742// tree map (based on red-black tree)
750- import java.util. TreeMap ;
751- var map = new TreeMap<Integer , Integer > ();
752- var map = new TreeMap<Integer , Integer > (Collections . reverseOrder());
753- var map = new TreeMap<String , Integer > (Map . of(" a" , 1 , " b" , 2 , " c" , 3 ));
743+ Map<Integer , Integer > map = new TreeMap<> ();
744+ Map<Integer , Integer > map = new TreeMap<> (Collections . reverseOrder());
745+ Map<String , Integer > map = new TreeMap<> (Map . of(" a" , 1 , " b" , 2 , " c" , 3 ));
754746put(" a" , 1 ), putIfAbsent(" b" , 2 ), get(" a" ), getOrDefault(" f" , 6 ), remove(" a" ), size(), isEmpty(),
755747keySet(), values(), entrySet(), containsKey(" a" ), containsValue(1 ), replace(" a" , 2 ), clear()
756748firstKey(), lastKey(), lowerKey(" b" ), higherKey(" b" ), floorKey(" b" ), ceilingKey(" b" ),pollFirstEntry(), pollLastEntry(),
757749headMap(" c" ), tailMap(" c" ), subMap(" a" , " c" ), descendingMap(), descendingKeySet()
758750
759751// tree set (based on red-black tree)
760- import java.util. TreeSet ;
761- var set = new TreeSet<Integer > ();
762- var set = new TreeSet<Integer > (Collections . reverseOrder());
763- var set = new TreeSet<Integer > (List . of(1 , 2 , 3 , 4 , 5 ));
752+ Set<Integer > set = new TreeSet<> ();
753+ Set<Integer > set = new TreeSet<> (Collections . reverseOrder());
754+ Set<Integer > set = new TreeSet<> (List . of(1 , 2 , 3 , 4 , 5 ));
764755add(1 ), remove(1 ), size(), isEmpty(), contains(1 ), clear(), iterator(), descendingIterator(),
765756first(), last(), lower(3 ), higher(3 ), floor(3 ), ceiling(3 ), pollFirst(), pollLast(),
766757headSet(3 ), tailSet(3 ), subSet(2 , 4 ), descendingSet()
@@ -965,11 +956,11 @@ Long.toString(num, base) // long -> string with base
965956Long . bitCount(42 ) // number of 1-bits
966957
967958// bitset
968- import java.util. BitSet ;
959+ import java. util. * ;
969960new BitSet (16 ), set(0 ), set(0 , 8 ), set(0 , 8 , true )
970961
971962// hex digits
972- import java.util. HexFormat ;
963+ import java. util. * ;
973964HexFormat hex = HexFormat . of();
974965byte b = 127 ;
975966String byteStr = hex. toHexDigits(b);
@@ -1035,16 +1026,15 @@ bisect.bisect_left(number_list, 3), bisect.bisect_right(number_list, 3), bisect.
10351026
10361027```java
10371028import java. util. * ;
1038- var array = new int []{1 , 2 , 3 , 4 , 5 };
1039- var arrayList = new ArrayList<Integer > (List . of(1 , 2 , 3 , 4 , 5 ));
1040- var linkedList = new LinkedList<Integer > (List . of(1 , 2 , 3 , 4 , 5 ));
1041- var hashSet = new HashSet<Integer > (List . of(1 , 2 , 3 , 4 , 5 ));
1042- var linkedHashSet = new LinkedHashSet<Integer > (List . of(1 , 2 , 3 , 4 , 5 ));
1043- var treeSet = new TreeSet<Integer > (List . of(1 , 2 , 3 , 4 , 5 ));
1029+
1030+ int [] array = new int []{1 , 2 , 3 , 4 , 5 };
1031+ List<Integer > arrayList = new ArrayList<> (List . of(1 , 2 , 3 , 4 , 5 ));
1032+ List<Integer > linkedList = new LinkedList<> (List . of(1 , 2 , 3 , 4 , 5 ));
1033+ Set<Integer > hashSet = new HashSet<> (List . of(1 , 2 , 3 , 4 , 5 ));
1034+ Set<Integer > linkedHashSet = new LinkedHashSet<> (List . of(1 , 2 , 3 , 4 , 5 ));
1035+ Set<Integer > treeSet = new TreeSet<> (List . of(1 , 2 , 3 , 4 , 5 ));
10441036
10451037// binary search
1046- import java.util. Arrays ;
1047- import java.util. Collections ;
10481038Arrays . binarySearch(array, 3 ) // for array
10491039Collections . binarySearch(arrayList, 3 ); // for list
10501040```
@@ -1092,13 +1082,15 @@ result = sorted(number_list) # return a new list(copy)
10921082`Arrays . sort()` and `Collections . sort()` sort the array and list in ascending order in- place.
10931083
10941084```java
1095- import java.util. Arrays ;
1085+ import java. util. * ;
1086+
1087+ // Arrays
10961088Arrays . sort(arr); // dual pivot quick sort (primitive types)
10971089 // timsort (insertion sort + merge sort) (reference types)
10981090Arrays . sort(arr, Comparator . comparingInt(String :: length));
10991091Arrays . sort(arr, Comparator . comparingInt(String :: length). reversed());
11001092
1101- import java.util . Collections;
1093+ // Collections
11021094Collections . sort(list); // timsort (insertion sort + merge sort)
11031095list. sort(Comparator . naturalOrder());
11041096list. sort(Comparator . reverseOrder());
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