Вы можете использовать API коллекции последней версии Java 6 для навигации по наборам и коллекциям карт. Эти API предоставляют большую гибкость для получения требуемого результата из коллекции.
1. Пример навигационной карты
package com.example.collection; import java.util.NavigableMap; import java.util.TreeMap; public class NavigableMapDemo { public static void main(String[] args) { NavigableMapnavigableMap=new TreeMap (); navigableMap.put("X", 500); navigableMap.put("B", 600); navigableMap.put("A", 700); navigableMap.put("T", 800); navigableMap.put("Y", 900); navigableMap.put("Z", 200); System.out.printf("Descending Set : %s%n",navigableMap.descendingKeySet()); System.out.printf("Floor Entry : %s%n",navigableMap.floorEntry("L")); System.out.printf("First Entry : %s%n",navigableMap.firstEntry()); System.out.printf("Last Key : %s%n",navigableMap.lastKey()); System.out.printf("First Key : %s%n",navigableMap.firstKey()); System.out.printf("Original Map : %s%n",navigableMap); System.out.printf("Reverse Map : %s%n",navigableMap.descendingMap()); } }
Выход
Descending Set : [Z, Y, X, T, B, A] Floor Entry : B=600 First Entry : A=700 Last Key : Z First Key : A Original Map : {A=700, B=600, T=800, X=500, Y=900, Z=200} Reverse Map : {Z=200, Y=900, X=500, T=800, B=600, A=700}
2. Пример набора навигации
package com.example.collection; import java.util.Arrays; import java.util.Iterator; import java.util.NavigableSet; import java.util.TreeSet; public class NavigableSetDemo { public static void main(String[] args) { NavigableSetnavigableSet = new TreeSet (Arrays.asList( "X", "B", "A", "Z", "T")); Iterator iterator = navigableSet.descendingIterator(); System.out.println("Original Set :"); while (iterator.hasNext()) { System.out.println(iterator.next()); } iterator = navigableSet.iterator(); System.out.println("Sorted Navigable Set :"); while (iterator.hasNext()) { System.out.println(iterator.next()); } System.out.printf("Head Set : %s.%n", navigableSet.headSet("X")); System.out.printf("Tail Set : %s.%n", navigableSet.tailSet("T", false)); System.out.printf("Sub Set : %s.%n", navigableSet.subSet("B", true, "X", true)); System.out.printf("Last Element : %s%n", navigableSet.last()); System.out.printf("First Element : %s%n", navigableSet.first()); System.out.printf("Reverse Set : %s%n", navigableSet.descendingSet()); System.out.printf("Original Set : %s%n", navigableSet); } }
Выход
Original Set : Z X T B A Sorted Navigable Set : A B T X Z Head Set : [A, B, T]. Tail Set : [X, Z]. Sub Set : [B, T, X]. Last Element : Z First Element : A Reverse Set : [Z, X, T, B, A] Original Set : [A, B, T, X, Z]
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Оригинал: “https://mkyong.com/java/how-to-work-with-java-6s-navigableset-and-navigablemap/”