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| 8.17.4.Navigating (Searching) TreeSets and TreeMaps |
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import java.util.TreeSet;
public class MainClass {
public static void main(String[] args) {
TreeSet<Integer> times = new TreeSet<Integer>();
times.add(1205);
times.add(1505);
times.add(1545);
times.add(1830);
times.add(2010);
times.add(2100);
// Java 5 version
TreeSet<Integer> subset = new TreeSet<Integer>();
subset = (TreeSet) times.headSet(1600);
System.out.println("last before 4pm is: " + subset.last());
TreeSet<Integer> sub2 = new TreeSet<Integer>();
sub2 = (TreeSet) times.tailSet(2000);
System.out.println("first after 8pm is: " + sub2.first());
// Java 6 version using the new lower() and higher() methods
System.out.println("last before 4pm is: " + times.lower(1600));
System.out.println("first after 8pm is: " + times.higher(2000));
}
}
last before 4pm is: 1545
first after 8pm is: 2010
last before 4pm is: 1545
first after 8pm is: 2010
Important "Navigation" Related Methods
Method Description
TreeSet.ceiling(e) Returns the lowest element >= e
TreeMap.ceilingKey(key) Returns the lowest key >= key
TreeSet.higher(e) Returns the lowest element > e
TreeMap.higherKey(key) Returns the lowest key > key
TreeSet.floor(e) Returns the highest element <= e
TreeMap.floorKey(key) Returns the highest key <= key
TreeSet.lower(e) Returns the highest element < e
TreeMap.lowerKey(key) Returns the highest key < key
TreeSet.pollFirst() Returns and removes the first entry
TreeMap.pollFirstEntry() Returns and removes the first key-value pair
TreeSet.pollLast() Returns and removes the last entry
TreeMap.pollLastEntry() Returns and removes the last key-value pair
TreeSet.descendingSet() Returns a NavigableSet in reverse order
TreeMap.descendingMap() Returns a NavigableMap in reverse order
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