Why Can\'t I Create an Array of LinkedLists in Java and How Do I Fix It?

Creating an Array of LinkedLists in Java

In Java, questions arise when attempting to create an array of LinkedLists. When declaring an array like private LinkedList[] myMatrix, it's expected that an array can be allocated with the following line: myMatrix = new LinkedList[numRows]. However, this strategy results in an error stating that a generic array of LinkedList cannot be created.

This raises two issues:

1. What is the error causing this situation?
2. Why is the LinkedList type allowed in the array declaration if it cannot be created?

It's important to note that IntegerNode is a user-defined class in this scenario.

Resolution

The solution to this issue is to cast the type in the declaration to allow the array creation. The revised declaration should be:

myMatrix = (LinkedList<IntegerNode>[]) new LinkedList<?>[numRows];

Explanation

In Java, generic arrays are not directly supported. Instead, raw types (i.e., types without type parameters) are used. Casting the type allows the compiler to infer the correct generic type for the array.

So, the type LinkedList[] in the declaration is allowed, even though it can't be created directly. This is because the compiler considers it as a raw type, leaving it up to the programmer to cast it to the specific generic type that is needed.

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