Packages, access modifiers, and top-level classes: will this code compile?\n\npackage foo;\nimport java.util.Vector; // Line 2\nprivate class MyVector extends Vector {\n int i = 1; // Line 5\n public MyVector() {\n i = 2;\n }\n}\npublic class MyNewVector extends MyVector {\n public MyNewVector() {\n i = 4; // Line 15\n }\n public static void main (String args[]) {\n MyVector v = new MyNewVector(); // Line 19\n }\n}

Introduction / Context:
Here we test Java's rules for top-level class access modifiers within a package. Only public or package-private (no modifier) are allowed for top-level classes; private and protected are illegal at the top level.

Given Data / Assumptions:

• File declares package foo;.
• MyVector is declared as private class MyVector at top level (Line 3).
• MyNewVector is a public class extending MyVector.

Concept / Approach:
The Java Language Specification allows only two choices for top-level class visibility: public or no modifier (package-private). Any attempt to mark a top-level class as private is a compile-time error.

Step-by-Step Solution:
Encounter private class MyVector extends Vector at line 3. Compiler flags: “modifier private not allowed here” (or similar message). Compilation halts; subsequent lines are not relevant.

Verification / Alternative check:
Change private to no modifier (package-private) or move MyVector to a nested class inside another type if private scope is required.

Why Other Options Are Wrong:
There is nothing illegal at lines 5, 15, or 19 once line 3 is fixed. The failure is specifically due to the top-level private modifier.

Common Pitfalls:
Confusing inner class modifiers with top-level class modifiers; forgetting that only one public top-level class per file is allowed (matching file name).

Final Answer:
Compilation will fail at line 3.