JAVA EXAMPLE PROGRAMS

JAVA EXAMPLE PROGRAMS

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Program: How to copy Map content to another TreeMap?


Description:

Below example shows how to copy another collection entries to TreeMap. By using putAll() method, you can copy all entries from another collections to TreeMap.


Code:
package com.java2novice.treemap;

import java.util.TreeMap;

public class MyTreeMapCopy {

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

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

  1. Basic TreeMap Operations.
  2. How to iterate through TreeMap?
  3. How to copy Map content to another TreeMap?
  4. How to search a key in TreeMap?
  5. How to search a value in TreeMap?
  6. How to get all keys from TreeMap?
  7. How to get entry set from TreeMap?
  8. How to delete all elements from TreeMap?
  9. How to sort keys in TreeMap by using Comparator?
  10. How to sort keys in TreeMap by using Comparator with user define objects?
  11. How to get sorted sub-map from TreeMap?
  12. How to get first key element from TreeMap (Sorted Map)?
  13. How to get last key element from TreeMap (Sorted Map)?
  14. How to reverse sorted keys in a TreeMap?
Knowledge Centre
String Vs StringBuffer
We know that String is immutable object. We can not change the value of a String object once it is initiated. If we try to change the value of the existing String object then it creates new object rather than changing the value of the existing object. So incase, we are going to do more modificatios on String, then use StringBuffer. StringBuffer updates the existing objects value, rather creating new object.
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If you don’t make mistakes, you’re not working on hard enough problems. And that’s a big mistake.
-- Frank Wilczek

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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