JAVA EXAMPLE PROGRAMS

JAVA EXAMPLE PROGRAMS

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Program: How to delete all elements from TreeMap?


Description:

Below example shows how to delete all elements from the given TreeMap at one call. By calling clear() method, we can delete all key-value pairs from TreeMap.


Code:
package com.java2novice.treemap;

import java.util.TreeMap;

public class MyTreeMapClear {

	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("My TreeMap content:");
		System.out.println(hm);
		System.out.println("Clearing TreeMap:");
		hm.clear();
		System.out.println("Content After clear:");
		System.out.println(hm);
	}
}

Output:
My TreeMap content:
{first=FIRST INSERTED, second=SECOND INSERTED, third=THIRD INSERTED}
Clearing TreeMap:
Content After clear:
{}
<< Previous Program | Next Program >>

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
What is wrapper class?
Everything in java is an object, except primitives. Primitives are int, short, long, boolean, etc. Since they are not objects, they cannot return as objects, and collection of objects. To support this, java provides wrapper classes to move primitives to objects. Some of the wrapper classes are Integer, Long, Boolean, etc.
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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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