Heap pollution occurs when a variable of aparameterized type refers to an object that is not of thatparameterized type. This situation can only occur if the programperformed some operation that would give rise to an uncheckedwarning at compile-time. An unchecked warning is generatedif, either at compile-time (within the limits of the compile-timetype checking rules) or at runtime, the correctness of an operationinvolving a parameterized type (for example, a cast or method call)cannot be verified.