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/* Get Head Map from Java TreeMap example This Java Example shows how to get the portion of TreeMap whose keys are less than the specified key using headMap method of Java TreeMap class. */ import java.util.SortedMap; import java.util.TreeMap; public class GetHeadMapFromTreeMapExample { public static void main(String[] args) { //create TreeMap object TreeMap treeMap = new TreeMap(); //add key value pairs to TreeMap treeMap.put("1","One"); treeMap.put("3","Three"); treeMap.put("2","Two"); treeMap.put("5","Five"); treeMap.put("4","Four"); /* To get a Head Map from Java TreeMap use, SortedMap headMap(Object toKey) method of Java TreeMap class. This method returns the portion of TreeMap whose keys are less than toKey. Please note that, the SortedMap returned by this method is backed by the original TreeMap. So any changes made to SortedMap will be reflected back to original TreeMap. */ SortedMap sortedMap = treeMap.headMap("3"); System.out.println("Head Map Contains : " + sortedMap); /* Please also note that, - SortedMap throws IllegalArgumentException for any attempts to insert the key grater than or equal to toKey. - subMap throws ClassCastException, if toKey can not be compared using Map's Comparators */ } } /* Output would be Head Map Contains : {1=One, 2=Two} */ |
Great examples