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Get Size of Java HashMap Example

  1. /*
  2.   Get Size of Java HashMap Example
  3.   This Java Example shows how to get the size or nubmer of key value pairs
  4.   stored in HashMap using size method.
  5. */
  6.  
  7. import java.util.HashMap;
  8.  
  9. public class GetSizeOfHashMapExample{
  10.  
  11.   public static void main(String[] args) {
  12.    
  13.     //create HashMap object
  14.     HashMap hMap = new HashMap();
  15.    
  16.     /*
  17.       To get the size of HashMap use
  18.       int size() method of HashMap class. It returns the number of key value
  19.       pairs stored in HashMap object.    
  20.     */
  21.     System.out.println("Size of HashMap : " + hMap.size());
  22.    
  23.     //add key value pairs to HashMap using put method
  24.     hMap.put("1","One");
  25.     hMap.put("2","Two");
  26.     hMap.put("3","Three");
  27.     System.out.println("Size of HashMap after addition : " + hMap.size());
  28.    
  29.     //remove one element from HashMap using remove method
  30.     Object obj = hMap.remove("2");
  31.     System.out.println("Size of HashMap after removal : " + hMap.size());
  32.   }
  33. }
  34.  
  35. /*
  36. Output would be
  37. Size of HashMap : 0
  38. Size of HashMap after addition : 3
  39. Size of HashMap after removal : 2
  40. */