How to work with Java 6’s NavigableSet and NavigableMap
You can use latest Java 6’s Collection API to navigate a set and Map collections. These API gives a lot of flexibility to find out required result from the collection.
1. NavigableMap Example
package com.example.collection;
import java.util.NavigableMap;
import java.util.TreeMap;
public class NavigableMapDemo {
public static void main(String[] args) {
NavigableMap<String,Integer> navigableMap=new TreeMap<String, Integer>();
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());
}
}
Output
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. NavigableSet Example
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) {
NavigableSet<String> navigableSet = new TreeSet<String>(Arrays.asList(
"X", "B", "A", "Z", "T"));
Iterator<String> 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);
}
}
Output
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]
Download Source Code
Download it – Navigable-Collection-Example.zip (1kb)
Thank you very much for your code example!
It really helps me,
Needs more on new java collection API