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Program: Write an example for Collections.checkedMap() method.


Collections.checkedMap() method returns a dynamically typesafe view of the specified map. Any attempt to insert a mapping whose key or value have the wrong type will result in an immediate ClassCastException. Similarly, any attempt to modify the value currently associated with a key will result in an immediate ClassCastException, whether the modification is attempted directly through the map itself, or through a Map.Entry instance obtained from the map's entry set view.

package com.java2novice.collections;

import java.util.Collections;
import java.util.HashMap;
import java.util.Map;

public class MyCheckedMap {

	public static void main(String a[]){
		Map myMap = new HashMap();
		myMap.put("one", 1);
		myMap.put("two", 2);
		myMap.put("three", 3);
		myMap.put("four", 4);
		Map chkMap = Collections.checkedMap(myMap, String.class, Integer.class);
		System.out.println("Checked map content: "+chkMap);
		//you can add any type of elements to myMap object
		myMap.put(10, "ten");
		//you cannot add any type of elements to chkMap object, doing so
		//throws ClassCastException
		chkMap.put(10, "ten"); //throws ClassCastException

Checked map content: {two=2, one=1, three=3, four=4}
Exception in thread "main" java.lang.ClassCastException: Attempt to insert class java.lang.Integer key into
						collection with key type class java.lang.String
	at java.util.Collections$CheckedMap.typeCheck(
	at java.util.Collections$CheckedMap.put(
	at com.java2novice.collections.MyCheckedMap.main(
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List Of All Collections Class Sample Programs:

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  3. How to search user defined object from a List by using binary search?
  4. Write an example for Collections.checkedCollection() method.
  5. Write an example for Collections.checkedList() method.
  6. Write an example for Collections.checkedSet() method.
  7. Write an example for Collections.checkedMap() method.
  8. How to check there in no common element between two list objects by using Collections.disjoint() method?
  9. How to create empty list using Collections class?
  10. How to create empty set using Collections class?
  11. How to create empty map using Collections class?
  12. How to Enumeration for ArrayList object?
  13. How to fill or replace elements of a List or ArrayList?
  14. How to find repeated element cound (frequency) of a given collection?
  15. How to convert Enumeration to List object?
  16. How to get index of a sub list from another list?
  17. How to get last index of a sub list from another list?
  18. How to get max element from the given list?
  19. How to get min element from the given list?
  20. How to get max element of a list of user defined objects?
  21. How to get min element of a list of user defined objects?
  22. How to get max element of a list of user defined objects using Comparator?
  23. How to get min element of a list of user defined objects using Comparator?
  24. How to create multiple copies of a given object?
  25. How to replace all occurances of a given object in the list?
  26. How to rotate elements in the list by specified distance?
  27. How to create synchronized list?
  28. How to create synchronized set?
  29. How to create synchronized map?
Knowledge Centre
Exception Vs Error
An error is an irrecoverable condition occurring at runtime like out of memory error. These kind of jvm errors cannot be handled at runtime. Exceptions are because of condition failures, which can be handled easily at runtime.
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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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