D286 Java Fundamentals - Set 5 - Part 2

Correct Answer: How closely related the responsibilities within a single component are

High cohesion means a component's elements work together toward one clear purpose, which makes the component easier to understand, name, and reuse.

Correct Answer: Low coupling and high cohesion

Well-designed systems minimize dependencies between components while ensuring each component's internal parts are strongly related to a single purpose.

Correct Answer: A reusable solution to a commonly recurring design problem

A design pattern describes a proven general approach to a recurring design problem, providing shared vocabulary rather than code to copy verbatim.

Correct Answer: Only one instance of a class exists with global access

The Singleton pattern restricts a class to a single instance and provides a global access point, though it is often criticized for hindering testability.

Correct Answer: A method for creating objects without specifying exact concrete classes

A factory encapsulates object creation, letting calling code request an object by type or configuration without depending on specific concrete classes.

Correct Answer: Supplying a class's dependencies from outside rather than creating them internally

Dependency injection passes collaborators into a class rather than having it construct them, which decouples components and makes substitution for testing straightforward.

Correct Answer: Test doubles can be supplied in place of real dependencies

Because dependencies are provided externally, tests can inject mocks or stubs, isolating the unit under test from databases, networks, and other slow collaborators.

Correct Answer: It allows a fake implementation to substitute for the real one

Coding against an interface lets tests provide lightweight fake implementations, isolating the unit under test from external systems.

Correct Answer: Changing internal structure without altering external behavior

Refactoring improves internal design while preserving observable behavior. Behavior changes belong to feature work or bug fixing, which are distinct activities.

Correct Answer: They verify behavior is preserved through the restructuring

A reliable test suite gives confidence that restructuring has not changed observable behavior, which is what makes aggressive refactoring safe.

Correct Answer: The future cost of shortcuts taken in design or implementation

Technical debt is the accumulated future cost of expedient choices. Like financial debt it accrues interest, making later changes progressively more expensive.

Correct Answer: When a deliberate short-term trade-off is made and scheduled for repayment

Deliberate, documented debt taken to meet a genuine constraint can be sound, provided the team recognizes it and plans to repay it before it compounds.

Correct Answer: Consistent style that makes code easier to read across a team

Consistent formatting reduces cognitive load when reading unfamiliar code and eliminates trivial disagreements, letting reviews focus on substance.

Correct Answer: UpperCamelCase, such as CustomerAccount

Java classes use UpperCamelCase. Methods and variables use lowerCamelCase, and constants use ALL_CAPS with underscores.

Correct Answer: ALL_CAPS with underscores, such as MAX_SIZE

Constants, typically declared static final, use uppercase letters with underscores separating words, distinguishing them clearly from variables.

Correct Answer: Automating compilation, dependency management, and packaging

Build tools automate dependency resolution, compilation, testing, and packaging, producing reproducible builds without manual classpath management.

Correct Answer: An archive packaging compiled classes and resources for distribution

A JAR is a ZIP-format archive bundling compiled .class files and resources, optionally with a manifest making it directly executable.

Correct Answer: The list of locations where the JVM searches for classes

The classpath tells the JVM and compiler where to find class files and libraries. Misconfiguration causes ClassNotFoundException or NoClassDefFoundError.

Correct Answer: The JDK includes development tools such as the compiler; the JRE only runs programs

The JDK contains development tools including javac, while the JRE provides only the runtime environment needed to execute already-compiled Java programs.

Correct Answer: Compiled bytecode runs on any system with a compatible JVM

Java compiles to platform-neutral bytecode that any conforming JVM can execute, giving the write once, run anywhere property.