package sample;
/*
Get Set view of Keys from Java HashMap example
This Java Example shows how to get a Set of keys contained in HashMap
using keySet method of Java HashMap class.
*/
import java.util.HashMap;
import java.util.Iterator;
import java.util.Set;
public class GetSetViewOfKeysFromHashMapExample {
public static void main(String[] args) {
//create HashMap object
HashMap hMap = new HashMap();
//add key value pairs to HashMap
hMap.put("1", "One");
hMap.put("2", "Two");
hMap.put("3", "Three");
/*
get Set of keys contained in HashMap using
Set keySet() method of HashMap class
*/
Set st = hMap.keySet();
System.out.println("Set created from HashMap Keys contains :");
//iterate through the Set of keys
Iterator itr = st.iterator();
while (itr.hasNext()) System.out.println(itr.next());
/*
Please note that resultant Set object is backed by the HashMap.
Any key that is removed from Set will also be removed from
original HashMap object. The same is not the case with the element
addition.
*/
//remove 2 from Set
st.remove("2");
//check if original HashMap still contains 2
boolean blnExists = hMap.containsKey("2");
System.out.println("Does HashMap contain 2 ? " + blnExists);
}
}
/*
Output would be
Set created from HashMap Keys contains :
3
2
1
Does HashMap contain 2 ? false
*/
