Java Tutorial/Collections/NavigableMap

Create NavigableMap from TreeMap

import java.util.Calendar;
import java.util.Locale;
import java.util.Map;
import java.util.NavigableMap;
import java.util.TreeMap;
public class NavigableMapSample {
  public static void main(String args[]) {
    Calendar now = Calendar.getInstance();
    Locale locale = Locale.getDefault();
    Map<String, Integer> names = now.getDisplayNames(Calendar.DAY_OF_WEEK, Calendar.LONG, locale);
    NavigableMap<String, Integer> nav = new TreeMap<String, Integer>(names);
    System.out.printf("Whole list:%n%s%n", nav);
    System.out.printf("First key: %s\tFirst entry: %s%n", nav.firstKey(), nav.firstEntry());
  }
}

Get ceiling key from NavigableMap

import java.util.Calendar;
import java.util.Locale;
import java.util.Map;
import java.util.NavigableMap;
import java.util.TreeMap;
public class NavigableMapSample {
  public static void main(String args[]) {
    Calendar now = Calendar.getInstance();
    Locale locale = Locale.getDefault();
    Map<String, Integer> names = now.getDisplayNames(Calendar.DAY_OF_WEEK, Calendar.LONG, locale);
    NavigableMap<String, Integer> nav = new TreeMap<String, Integer>(names);
    System.out.printf("Whole list:%n%s%n", nav);
    System.out.printf("Key ceiling after Sunday: %s%n", nav.ceilingKey("Sunday"));
  }
}

Get first key and first entry from NavigableMap

import java.util.Calendar;
import java.util.Locale;
import java.util.Map;
import java.util.NavigableMap;
import java.util.TreeMap;
public class NavigableMapSample {
  public static void main(String args[]) {
    Calendar now = Calendar.getInstance();
    Locale locale = Locale.getDefault();
    Map<String, Integer> names = now.getDisplayNames(Calendar.DAY_OF_WEEK, Calendar.LONG, locale);
    NavigableMap<String, Integer> nav = new TreeMap<String, Integer>(names);
    System.out.printf("Whole list:%n%s%n", nav);
    System.out.printf("First key: %s\tFirst entry: %s%n", nav.firstKey(), nav.firstEntry());
  }
}

Get floor key from NavigableMap

import java.util.Calendar;
import java.util.Locale;
import java.util.Map;
import java.util.NavigableMap;
import java.util.TreeMap;
public class NavigableMapSample {
  public static void main(String args[]) {
    Calendar now = Calendar.getInstance();
    Locale locale = Locale.getDefault();
    Map<String, Integer> names = now.getDisplayNames(Calendar.DAY_OF_WEEK, Calendar.LONG, locale);
    NavigableMap<String, Integer> nav = new TreeMap<String, Integer>(names);
    System.out.printf("Whole list:%n%s%n", nav);
    System.out.printf("Key floor before Sunday: %s%n", nav.floorKey("Sunday"));
  }
}

Get higher key from NavigableMap

import java.util.Calendar;
import java.util.Locale;
import java.util.Map;
import java.util.NavigableMap;
import java.util.TreeMap;
public class NavigableMapSample {
  public static void main(String args[]) {
    Calendar now = Calendar.getInstance();
    Locale locale = Locale.getDefault();
    Map<String, Integer> names = now.getDisplayNames(Calendar.DAY_OF_WEEK, Calendar.LONG, locale);
    NavigableMap<String, Integer> nav = new TreeMap<String, Integer>(names);
    System.out.printf("Whole list:%n%s%n", nav);
    System.out.printf("Key higher after Sunday: %s%n", nav.higherKey("Sunday"));
  }
}

Get last key and last entry from NavigableMap

import java.util.Calendar;
import java.util.Locale;
import java.util.Map;
import java.util.NavigableMap;
import java.util.TreeMap;
public class NavigableMapSample {
  public static void main(String args[]) {
    Calendar now = Calendar.getInstance();
    Locale locale = Locale.getDefault();
    Map<String, Integer> names = now.getDisplayNames(Calendar.DAY_OF_WEEK, Calendar.LONG, locale);
    NavigableMap<String, Integer> nav = new TreeMap<String, Integer>(names);
    System.out.printf("Whole list:%n%s%n", nav);
    System.out.printf("Last key: %s\tLast entry: %s%n", nav.lastKey(), nav.lastEntry());
  }
}

Get lower key from NavigableMap

import java.util.Calendar;
import java.util.Locale;
import java.util.Map;
import java.util.NavigableMap;
import java.util.TreeMap;
public class NavigableMapSample {
  public static void main(String args[]) {
    Calendar now = Calendar.getInstance();
    Locale locale = Locale.getDefault();
    Map<String, Integer> names = now.getDisplayNames(Calendar.DAY_OF_WEEK, Calendar.LONG, locale);
    NavigableMap<String, Integer> nav = new TreeMap<String, Integer>(names);
    System.out.printf("Whole list:%n%s%n", nav);
    System.out.printf("Key lower before Sunday: %s%n", nav.lowerKey("Sunday"));
  }
}

Get navigable key set from NavigableMap

import java.util.Calendar;
import java.util.Locale;
import java.util.Map;
import java.util.NavigableMap;
import java.util.TreeMap;
public class NavigableMapSample {
  public static void main(String args[]) {
    Calendar now = Calendar.getInstance();
    Locale locale = Locale.getDefault();
    Map<String, Integer> names = now.getDisplayNames(Calendar.DAY_OF_WEEK, Calendar.LONG, locale);
    NavigableMap<String, Integer> nav = new TreeMap<String, Integer>(names);
    System.out.printf("Whole list:%n%s%n", nav);
    System.out.printf("Map before Sunday: %s%n", nav.navigableKeySet());
  }
}

NavigableMap Demo

import java.util.Calendar;
import java.util.Locale;
import java.util.Map;
import java.util.NavigableMap;
import java.util.TreeMap;
public class NavigableMapSample {
  public static void main(String args[]) {
    Calendar now = Calendar.getInstance();
    Locale locale = Locale.getDefault();
    Map<String, Integer> names = now.getDisplayNames(Calendar.DAY_OF_WEEK, Calendar.LONG, locale);
    NavigableMap<String, Integer> nav = new TreeMap<String, Integer>(names);
    System.out.printf("Whole list:%n%s%n", nav);
  }
}

The NavigableMap Interface

The java.util.NavigableMap interface, a new addition to Java 6, inherits SortedMap to add navigation methods that allows for key/value pair searching.

The java.util.TreeMap class in Java 6 implements NavigableMap.

import java.util.NavigableMap;
import java.util.TreeMap;
import java.util.Map.Entry;
public class NavigableMapDemo {
  public static void main(String[] args) {
    NavigableMap<Integer, String> map = new TreeMap<Integer, String>();
    map.put(2, "two");
    map.put(1, "one");
    map.put(3, "three");
    System.out.println("Original map: " + map + "\n");
    Entry firstEntry = map.pollFirstEntry();
    System.out.println("First entry: " + firstEntry);
    System.out.println("After polling the first entry: " + map + "\n");
    Entry lastEntry = map.pollLastEntry();
    System.out.println("Last entry:" + lastEntry);
    System.out.println("After polling last entry:" + map);
  }
}

Original map: {1=one, 2=two, 3=three}
First entry: 1=one
After polling the first entry: {2=two, 3=three}
Last entry:3=three
After polling last entry:{2=two}