Navigating (Searching) TreeSets and TreeMaps : TreeSet « Utility Classes « SCJP

1. SCJP
2. Utility Classes
3. TreeSet

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