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how to get all keys from hashtable in java?


Hashtable:

Hashtable extends Dictionary class and implements Map interface. It contains elements in key-value pair. It not allowed duplicate key. It is synchronized. It can’t contain null key or value. It uses hashcode() method for finding the position of the elements.

We can use keySet() method get all keys from hashtable in java. It returns a Set object with all keys.

Example:

package com.codesjava;
 
import java.util.Hashtable;
import java.util.Set;
 
public class Test {
  public static void main(String args[]){
	//Create Hashtable object.
	Hashtable<String, String> hashtable = new Hashtable<String, String>();
	//Add objects to the Hashtable.
	hashtable.put("1", "Jai");
	hashtable.put("2", "Mahesh");
	hashtable.put("3","Vivek");
        System.out.println(hashtable);
        Set<String> keys = hashtable.keySet();
        for(String key: keys){
            System.out.println(key);
        }
  }
}

Output

{3=Vivek, 2=Mahesh, 1=Jai}
3
2
1


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