TreeMap SortedMap subMap(K fromKey,K toKey) Method Example Program


Returns a view of the portion of this map whose keys range from fromKey, inclusive, to toKey, exclusive. (If fromKey and toKey are equal, the returned map is empty.) The returned map is backed by this map, so changes in the returned map are reflected in this map, and vice-versa. The returned map supports all optional map operations that this map supports.

Program

package com.candidjava;

import java.util.TreeMap;
import java.util.SortedMap;

/**
 * @author: Hari Haran
 * @discription: The subMap(K fromKey,K toKey) method is used to return a view
 *               of the portion of this map whose keys range from fromKey,
 *               inclusive, to toKey, exclusive. (If fromKey and toKey are
 *               equal, the returned map is empty.) The returned map is backed
 *               by this map, so changes in the returned map are reflected in
 *               this map, and vice-versa.
 */

public class TreeMapSubMap {
	public static void main(String[] args) {

		TreeMap<Integer, String> tm = new TreeMap<Integer, String>();
		SortedMap<Integer, String> tmin = new TreeMap<Integer, String>();

		tm.put(1, "Anand");
		tm.put(2, "Hari Haran");
		tm.put(8, "Kamal");
		tm.put(4, "Karthikeyan");
		tm.put(5, "Mohan");
		tm.put(6, "Vinoth");
		tm.put(7, "Hari Haran");

		System.out.println("Getting a portion of the map");
		tmin = tm.subMap(1, 5);
		System.out.println("Sub map values: " + tmin);
	}
}

Output

Getting a portion of the map
Sub map values: {1=Anand, 2=Hari Haran, 4=Karthikeyan}

Explanation

public SortedMap<K,V> subMap(K fromKey, K toKey)
Returns a view of the portion of this map whose keys range from fromKey, inclusive, to toKey, exclusive. (If fromKey and toKey are equal, the returned map is empty.) The returned map is backed by this map, so changes in the returned map are reflected in this map, and vice-versa. The returned map supports all optional map operations that this map supports.
The returned map will throw an IllegalArgumentException on an attempt to insert a key outside its range.

Equivalent to subMap(fromKey, true, toKey, false).

Specified by:
subMap in interface NavigableMap<K,V>
Specified by:
subMap in interface SortedMap<K,V>
Parameters:
fromKey - low endpoint (inclusive) of the keys in the returned map
toKey - high endpoint (exclusive) of the keys in the returned map
Returns:
a view of the portion of this map whose keys range from fromKey, inclusive, to toKey, exclusive
Throws:
ClassCastException - if fromKey and toKey cannot be compared to one another using this map's comparator (or, if the map has no comparator, using natural ordering). Implementations may, but are not required to, throw this exception if fromKey or toKey cannot be compared to keys currently in the map.
NullPointerException - if fromKey or toKey is null and this map uses natural ordering, or its comparator does not permit null keys
IllegalArgumentException - if fromKey is greater than toKey; or if this map itself has a restricted range, and fromKey or toKey lies outside the bounds of the range


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