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Program: How to get all keys from Hashtable?


Description:

Below example shows how to get list of keys. keySet() method returns Set object will all keys.


Code:
package com.java2novice.hashtable;

import java.util.Hashtable;
import java.util.Set;

public class MyHashtableKeys {

	public static void main(String a[]){
		Hashtable<String, String> hm = new Hashtable<String, String>();
		//add key-value pair to Hashtable
		hm.put("first", "FIRST INSERTED");
		hm.put("second", "SECOND INSERTED");
		hm.put("third","THIRD INSERTED");
		System.out.println(hm);
		Set<String> keys = hm.keySet();
		for(String key: keys){
			System.out.println(key);
		}
	}
}


Output:
{third=THIRD INSERTED, second=SECOND INSERTED, first=FIRST INSERTED}
third
second
first
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List Of All Hashtable Sample Programs:

  1. Basic Hashtable Operations.
  2. How to iterate through Hashtable?
  3. How to copy Map content to another Hashtable?
  4. How to search a key in Hashtable?
  5. How to search a value in Hashtable?
  6. How to get all keys from Hashtable?
  7. How to get entry set from Hashtable?
  8. How to delete all elements from Hashtable?
  9. How to read elements using Enumeration in Hashtable?
  10. Hashtable implementation with equals and hashcode example.
  11. How to fetch values with user define object as keys in Hashtable?
  12. How to eliminate duplicate keys (user defined objects) with Hashtable?
Knowledge Centre
Different types of Access Modifiers
public: Any thing declared as public can be accessed from anywhere.

private: Any thing declared as private can't be seen outside of its class.

protected: Any thing declared as protected can be accessed by classes in the same package and subclasses in the other packages.

default modifier: Can be accessed only to classes in the same package.
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About Author

I'm Nataraja Gootooru, programmer by profession and passionate about technologies. All examples given here are as simple as possible to help beginners. The source code is compiled and tested in my dev environment.

If you come across any mistakes or bugs, please email me to [email protected].

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Reference: Java™ Platform Standard Ed. 7 - API Specification | Java™ Platform Standard Ed. 8 - API Specification | Java is registered trademark of Oracle.
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