/* package whatever; // don't place package name! */
 
import java.util.*;
import java.lang.*;
import java.io.*;
 
/* Name of the class has to be "Main" only if the class is public. */
class Ideone
{
	public static void main (String[] args) throws java.lang.Exception
	{
List<Map<Integer,Double>> list = new ArrayList<>();
// Cast to raw List to disable type checking, so the example compiles.
List<Map<? extends Number,? extends Number>> listX = (List) list;  
 
Map<Double,Integer> map = new HashMap<>();
map.put(0.0, 0);
 
listX.add(map);
 
for (Map<Integer, Double> e : list) {
  Integer i = e.keySet().iterator().next();  // ClassCastException!
}
 
	}
}

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