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Program: How to copy Map content to another HashMap?


Description:

Below example shows how to copy another collection to HashMap. putAll() method helps us to copy another collections to HashMap object.


Code:
package com.java2novice.hashmap;

import java.util.HashMap;

public class MyHashMapCopy {

	public static void main(String a[]){
		HashMap<String, String> hm = new HashMap<String, String>();
		//add key-value pair to hashmap
		hm.put("first", "FIRST INSERTED");
		hm.put("second", "SECOND INSERTED");
		hm.put("third","THIRD INSERTED");
		System.out.println(hm);
		HashMap<String, String> subMap = new HashMap<String, String>();
		subMap.put("s1", "S1 VALUE");
		subMap.put("s2", "S2 VALUE");
		hm.putAll(subMap);
		System.out.println(hm);
	}
}

Output:
{second=SECOND INSERTED, third=THIRD INSERTED, first=FIRST INSERTED}
{s2=S2 VALUE, s1=S1 VALUE, second=SECOND INSERTED, third=THIRD INSERTED, first=FIRST INSERTED}
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List Of All HashMap Sample Programs:

  1. Basic HashMap Operations.
  2. How to iterate through HashMap?
  3. How to copy Map content to another HashMap?
  4. How to search a key in HashMap?
  5. How to search a value in HashMap?
  6. How to get all keys from HashMap?
  7. How to get entry set from HashMap?
  8. How to delete all elements from HashMap?
  9. How to eliminate duplicate user defined objects as a key from HashMap?
  10. How to find user defined objects as a key from HashMap?
  11. How to delete user defined objects as a key from HashMap?
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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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