JAVA EXAMPLE PROGRAMS

JAVA EXAMPLE PROGRAMS

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Program: How to iterate through TreeMap?


Description:

Below example shows how to iterate through all entries from the TreeMap. First you can get all keys by calling keySet() method, which returns list of keys as Set object. By going through each element in the set, you can get corresponding values from TreeMap.


Code:
package com.java2novice.treemap;

import java.util.Set;
import java.util.TreeMap;

public class MyTreeMapRead {

	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);
		Set<String> keys = hm.keySet();
		for(String key: keys){
			System.out.println("Value of "+key+" is: "+hm.get(key));
		}
	}
}

Output:
{first=FIRST INSERTED, second=SECOND INSERTED, third=THIRD INSERTED}
Value of first is: FIRST INSERTED
Value of second is: SECOND INSERTED
Value of third is: 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
Difference between Enumeration and Iterator
The functionality of Enumeration and the Iterator are same. You can get remove() from Iterator to remove an element, while while Enumeration does not have remove() method. Using Enumeration you can only traverse and fetch the objects, where as using Iterator we can also add and remove the objects. So Iterator can be useful if you want to manipulate the list and Enumeration is for read-only access.
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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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