Giving The Following Code Snippet: Discuss The Reasons For U ✓ Solved

Giving the following code snippet: Discuss the reasons of us

Giving the following code snippet: Discuss the reasons of using private access specifier in some places of the code and public in other places. Additionally, discuss how can you test this code.

Paper For Above Instructions

Introduction

The Book class shown is a small Java data model whose fields are declared private and whose constructor and accessor methods are public. Choosing private for some members and public for others is a deliberate design decision rooted in encapsulation, API design, maintainability, and testability. This paper explains the reasons for those access choices and describes practical ways to test the class, with concrete testing patterns and recommendations.

Why use private for fields?

Declaring the fields bookName, ed, and author as private enforces encapsulation: it hides internal representation from clients and exposes a controlled public interface (getters and behaviors) instead (Bloch, 2018). Encapsulation provides multiple practical benefits. First, it prevents external code from directly mutating internal state, reducing unintended side effects and helping the class maintain invariants (Martin, 2008). For example, if the edition must always be positive, keeping ed private prevents arbitrary code from setting it to an invalid value.

Second, information hiding gives the class implementer freedom to change internal representation without breaking callers. If the author field needed to change from String to a structured Author object later, the class could adapt internally while keeping the public accessor contract stable (McConnell, 2004; Gamma et al., 1994). This reduces coupling and improves long-term maintainability and binary compatibility (Oracle Java SE Documentation, Access Control).

Third, private fields encourage a behavioral API orientation (methods that express intent) rather than exposing raw data. This promotes clearer abstractions and better readability (Fowler, 2018).

Why use public for constructor and accessors?

The constructor and accessor methods are public because they are the class’s service surface: they are the legitimate ways for other code to create and read Book instances. A public constructor is necessary so client code can instantiate the object (or a factory method could be provided as an alternative) (Bloch, 2018). Public getters provide read access while preserving control over representation. By making getters public instead of exposing fields, the class can perform lazy computation, validation, formatting, or convert internal structures to API-friendly forms without breaking callers (Fowler, 2018).

Public methods also support reasoning about contract and responsibility. For example, printBookDetails is a convenience behavior that outputs a formatted representation. Keeping it public provides a clear, discoverable capability of Book while still not exposing the internal fields directly.

When might other access levels be appropriate?

Package-private or protected access may be used when members should be visible to test helpers or subclasses but not to general clients. However, prefer minimal exposure: favor private for state and public for well-defined operations unless there is a compelling reason to widen visibility (Liskov & Wing, 1994; Martin, 2008).

Testing strategy: principles

Unit tests should verify externally observable behavior through the public API rather than testing private implementation details. Tests that depend on private fields are brittle and hinder refactoring (McConnell, 2004). Therefore test the constructor, getters, and printBookDetails by exercising public methods and asserting expected results.

Where direct output to System.out is used (as in printBookDetails), prefer refactoring to improve testability: either return a String with the formatted details (and let callers print it) or accept a PrintStream/Writer dependency so tests can inject a test double (Fowler, 2018). If refactoring is not possible, capture stdout in the test process to assert printed content.

Concrete test cases and techniques

1) Constructor and getters: write JUnit tests that build a Book instance and assert the getters return the values passed to the constructor.

Example assertions: assertEquals("Title", book.getBookName()); assertEquals(2, book.getBookEd()); assertEquals("Author Name", book.getAuthor()) (JUnit 5 User Guide).

2) printBookDetails: two approaches

  • Refactor to return String: change printBookDetails toString or a method that returns formatted text; test the returned String directly (Bloch, 2018; Fowler, 2018).
  • Capture System.out: in a unit test redirect System.out to a ByteArrayOutputStream, invoke printBookDetails, then assert the captured output contains expected lines (JUnit 5 + standard Java I/O).

3) Invariants and invalid inputs: if you add validation (e.g., non-null name, positive edition), write tests that assert exceptions are thrown for invalid inputs (assertThrows in JUnit 5) (JUnit 5 User Guide).

4) Integration tests: verify Book participates correctly when used by higher-level components (e.g., serialization, persistence). These tests validate that the public API integrates as intended (Pressman, 2014).

5) Avoid testing private fields: if you absolutely must confirm an internal detail, use reflection carefully or, preferably, expose the required behavior via the public API. Testing via reflection couples tests to implementation and is generally discouraged (McConnell, 2004).

Testing code examples (patterns)

Unit test for getters (JUnit 5): instantiate Book and assert getters. For printBookDetails without refactor: use ByteArrayOutputStream and System.setOut(new PrintStream(baos)), call printBookDetails(), then convert baos to string and assert lines. For behavior-driven tests, prefer asserting on returned values or toString output rather than console text (Martin, 2008).

Design recommendations to improve testability and robustness

- Prefer immutability for simple value objects: make fields final if they are never reassigned to express intent and to make reasoning and testing easier (Bloch, 2018).

- Consider overriding toString() to provide a machine- and test-friendly representation and keep printing logic out of the model class (clean separation of concerns) (Fowler, 2018).

- Add input validation in the constructor with clear exceptions so tests can assert invalid inputs fail early (McConnell, 2004).

Conclusion

Using private for fields and public for constructor and accessors follows established object-oriented design principles: it enforces encapsulation, reduces coupling, improves maintainability, and enables safer evolution of the implementation (Bloch, 2018; Oracle Docs). Testing should focus on the public API: verify constructor behavior, getters, printed or returned representations, and invariants via unit tests (JUnit). When methods write to System.out, prefer refactoring (returning strings or injecting streams) to make tests simpler and less brittle. These practices together yield clearer, more robust, and more easily testable code.

References

  • Bloch, J. (2018). Effective Java (3rd ed.). Addison-Wesley.
  • Oracle. Java Platform, Standard Edition Documentation: Access Control. https://docs.oracle.com/javase/tutorial/java/javaOO/accesscontrol.html
  • Gamma, E., Helm, R., Johnson, R., & Vlissides, J. (1994). Design Patterns: Elements of Reusable Object-Oriented Software. Addison-Wesley.
  • McConnell, S. (2004). Code Complete (2nd ed.). Microsoft Press.
  • Fowler, M. (2018). Refactoring: Improving the Design of Existing Code (2nd ed.). Addison-Wesley.
  • Martin, R. C. (2008). Clean Code: A Handbook of Agile Software Craftsmanship. Prentice Hall.
  • Liskov, B., & Wing, J. M. (1994). A behavioral notion of subtyping. ACM Transactions on Programming Languages and Systems.
  • JUnit 5 Team. JUnit 5 User Guide. https://junit.org/junit5/docs/current/user-guide/
  • Pressman, R. S. (2014). Software Engineering: A Practitioner's Approach (8th ed.). McGraw-Hill Education.
  • Martin, R. C. (2002). Agile Software Development: Principles, Patterns, and Practices. Prentice Hall.

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