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Simple Java TreeMap example

  1. /*
  2.   Simple Java TreeMap example
  3.   This simple Java Example shows how to use Java TreeMap. It also describes how to
  4.   add something to TreeMap and how to retrieve the value added from TreeMap.
  5. */
  6.  
  7. import java.util.TreeMap;
  8.  
  9. public class JavaTreeMapExample {
  10.  
  11.   public static void main(String[] args) {
  12.    
  13.     //create object of TreeMap
  14.     TreeMap treeMap = new TreeMap();
  15.    
  16.     /*
  17.       Add key value pair to TreeMap using,
  18.       Object put(Object key, Object value) method of Java TreeMap class,
  19.       where key and value both are objects
  20.       put method returns Object which is either the value previously tied
  21.       to the key or null if no value mapped to the key.
  22.     */
  23.    
  24.     treeMap.put("One", new Integer(1));
  25.     treeMap.put("Two", new Integer(2));
  26.    
  27.     /*
  28.       Please note that put method accepts Objects. Java Primitive values CAN NOT
  29.       be added directly to TreeMap. It must be converted to corrosponding
  30.       wrapper class first.
  31.     */
  32.    
  33.     //retrieve value using Object get(Object key) method of Java TreeMap class
  34.     Object obj = treeMap.get("Two");
  35.     System.out.println(obj);  
  36.    
  37.     /*
  38.       Please note that the return type of get method is an Object. The value must
  39.       be casted to the original class.
  40.     */
  41.   }
  42. }
  43. /*
  44. Output of the program would be
  45. 2
  46. */