Challenge 2: Attempting new T() Inside a Generic Class — Possible Solution
====================================================================

Broken attempt — Pair.java:

public class Pair<T> {
    private T first;
    private T second;

    public T createDefault() {
        T value = new T();   // attempting to instantiate the type parameter
        return value;
    }
}

Representative compile error:

    Pair.java:5: error: unexpected type
            T value = new T();
                          ^
      required: class
      found:    type parameter T
      where T is a type-variable:
        T extends Object declared in class Pair

Explanation:
By the time Pair's bytecode exists, T has been erased -- there is no
real class left at runtime for `new T()` to instantiate. `new`
requires a genuine, concrete class to allocate; T is only ever a
compile-time placeholder telling the compiler what type checking to
perform, not something that survives into the compiled class file.
The compiler catches this immediately, rather than letting it fail at
runtime, because it already knows T won't exist by then.

WHY THIS WORKS AS AN ANSWER
------------------------------
This reproduces exactly the `new T()` limitation the chapter names as
a direct consequence of erasure, and the explanation ties the failure
back to the chapter's own claim that the type argument doesn't exist
at runtime, so there's nothing concrete for `new` to construct.