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$CheckedMap.typeCheck(Collections.java:2547)
	at java.util.Collections$CheckedMap.put(Collections.java:2579)
	at com.java2novice.collections.MyCheckedMap.main(MyCheckedMap.java:22)