Numerous articles contrast the technical aspects of C++ and Java, but which disparities are most crucial for developers? For instance, what are the implications of Java’s lack of multiple inheritance support, a feature present in C++? Is this difference beneficial or not? Opinions vary, with some advocating for Java’s approach while others perceive it as a limitation.

This article aims to guide developers in determining when to choose C++, Java, or an alternative language, emphasizing the reasons behind such decisions.

Fundamentals: Language Construction and Ecosystems

Launched in 1985, C++ acted as a front end for C compilers, similar to how TypeScript compiles to JavaScript. Today’s C++ compilers generally produce native machine code. Although some argue that C++’s compilers hinder portability due to the need for recompilation for different architectures, C++ code enjoys broad compatibility across almost all processor platforms.

Introduced in 1995, Java doesn’t directly compile to native code. Instead, it generates bytecode, an intermediary binary representation executed by the Java Virtual Machine (JVM). This means the output of the Java compiler requires a platform-specific executable to run.

Both C++ and Java belong to the C-like language family, sharing a syntactic resemblance to C. Their primary distinction lies in their ecosystems. While C++ seamlessly integrates with libraries based on C, C++, or operating system APIs, Java excels when working with Java-based libraries. Accessing C libraries from Java is possible via the Java Native Interface (JNI) API, but this method is prone to errors and necessitates some C or C++ code. As a lower-level language, C++ interacts with hardware more readily than Java.

Weighing the Trade-offs: Generics, Memory, and Beyond

Comparing C++ and Java can be multifaceted. In certain scenarios, the choice is straightforward. Native Android applications typically favor Java, except for games, where developers often opt for C++ or another language for smoother real-time animation. Java’s memory management often introduces lag during gameplay.

This discussion excludes cross-platform applications outside of gaming. Neither C++ nor Java proves ideal for such cases due to their verbosity, which hinders efficient GUI development. High-performance applications benefit from C++ modules for demanding tasks, combined with a more developer-friendly language for GUI development.

Cross-platform applications that aren’t games are beyond the scope of this discussion. Neither C++ nor Java are ideal in this case because they’re too verbose for efficient GUI development.

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When the choice remains unclear, further comparison is necessary:

Beyond the table’s comparisons, we’ll delve into object-oriented programming (OOP) features such as multiple inheritance, generics/templates, and reflection. Both languages support OOP: Java mandates it, while C++ offers OOP alongside global functions and static data.

Multiple Inheritance

In OOP, inheritance allows a child class to inherit attributes and methods from a parent class. A classic example is a Rectangle class inheriting from a more general Shape class:

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// Note that we are in a C++ file
class Shape {
    // Position
    int x, y;
  public:
    // The child class must override this pure virtual function
    virtual void draw() = 0;
};
 
class Rectangle: public Shape {
    // Width and height
    int w, h;
  public:
    void draw();
};

Multiple inheritance occurs when a child class inherits from several parents. Consider this example, utilizing the Rectangle and Shape classes along with a Clickable class:

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// Not recommended
class Shape {...};
class Rectangle: public Shape {...};
 
class Clickable {
    int xClick, yClick;
  public:
    virtual void click() = 0;
};
 
class ClickableRectangle: public Rectangle, public Clickable {
    void click();
};

Here, we have two base types: Shape (the base of Rectangle) and Clickable. ClickableRectangle inherits from both, combining the two object types.

C++ supports multiple inheritance, while Java does not. Although generally discouraged, multiple inheritance proves useful in specific edge cases, such as:

• Developing advanced domain-specific languages (DSLs).
• Performing complex calculations during compilation.
• Enhancing project type safety in ways unattainable in Java.

However, multiple inheritance can complicate code and impact performance unless combined with template metaprogramming, a technique best left to experienced C++ programmers.

Generics and Templates

Generic class implementations that work with any data type are valuable for code reuse. Both languages provide this support—Java through generics, C++ through templates—but the flexibility of C++ templates enhances safety and robustness in advanced programming. C++ compilers generate specialized classes or functions for each distinct type used with a template. Moreover, C++ templates can invoke custom functions based on the types of parameters passed to the top-level function, enabling specialized code for specific data types. This is known as template specialization. Java lacks an equivalent feature.

Conversely, Java compilers employ type erasure to create general, type-agnostic objects when using generics. While Java performs type checking during compilation, programmers cannot modify the behavior of a generic class or method based on its type parameters. To illustrate this, let’s examine a simple example of a generic std::string format(std::string fmt, T1 item1, T2 item2) function utilizing a template, template<class T1, class T2>, from a custom C++ library:

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std::string firstParameter = "A string";
int secondParameter = 123;
// Format printed output as an eight-character-wide string and a hexadecimal value
format("%8s %x", firstParameter, secondParameter);
// Format printed output as two eight-character-wide strings
format("%8s %8s", firstParameter, secondParameter);

C++ would generate the format function as std::string format(std::string fmt, std::string item1, int item2), whereas Java would create it without specific string and int types for item1 and item2. In this case, our C++ template recognizes that the final parameter is an int and performs the necessary std::to_string conversion in the second format call. Without templates, a C++ printf statement attempting to print a number as a string (as in the second format call) would result in undefined behavior, potentially crashing the application or producing garbage output. The Java function could only handle a number as a string in the first format call and wouldn’t directly format it as a hexadecimal integer. While this example is basic, it highlights C++’s ability to utilize a specialized template for any arbitrary class object without altering the class itself or the format function. Achieving the correct output in Java would require reflection instead of generics, a less extensible and more error-prone approach.

Reflection

Java allows runtime discovery of structural details like available members in a class or class type. This feature is called reflection, possibly because it’s like reflecting on the object’s structure. (More information can be found in Oracle’s reflection documentation.)

While lacking full reflection, modern C++ provides runtime type information (RTTI). RTTI enables runtime detection of specific object types, but it cannot access information like the object’s members.

Memory Management

Another crucial difference lies in memory management, which has two primary approaches: manual, where developers handle memory allocation and release; and automatic, where software tracks object usage to recycle unused memory. One example in Java is garbage collection.

Java mandates garbage-collected memory, simplifying memory management compared to the manual approach and eliminating memory-related errors that often lead to security vulnerabilities. While C++ doesn’t natively offer automatic memory management, it supports a form of garbage collection known as smart pointers. These smart pointers employ reference counting, providing security and performance when used correctly. C++ also offers destructors to clean up or release resources when an object is destroyed.

While Java only permits heap allocation, C++ supports both heap allocation (using new and delete or the older C malloc functions) and stack allocation. Stack allocation can be faster and safer than heap allocation due to the stack’s linear data structure compared to the heap’s tree-based structure. This simplicity makes stack memory allocation and release more straightforward.

Another C++ advantage related to stack allocation is Resource Acquisition Is Initialization (RAII), a programming technique where resources (e.g., references) are tied to their controlling object’s life cycle. These resources are then automatically destroyed at the end of that object’s life cycle. RAII underpins the functionality of C++ smart pointers without manual dereferencing. For instance, a smart pointer referenced at the beginning of a function is automatically dereferenced upon exiting the function, releasing the associated memory if it’s the last reference to that smart pointer. Although Java offers a similar pattern, it’s considered it’s more awkward than C++’s RAII, particularly when creating multiple resources within the same code block.

Runtime Performance

Despite Java’s respectable runtime performance, C++ reigns supreme. Manual memory management proves faster than garbage collection in real-world applications. While Java can outperform C++ in specific scenarios due to JIT compilation, C++ prevails in most non-trivial cases.

Specifically, Java’s standard memory library, with its garbage collector, tends to over-allocate compared to C++’s more conservative heap allocation strategy. However, Java’s speed remains relatively high and should suffice unless latency is paramount, such as in games or applications with real-time constraints.

Build and Package Management

Java compensates for its performance shortcomings with its user-friendliness. One contributing factor is build and package management—the process of building projects and incorporating external dependencies. Java simplifies this with a tool called Maven, which integrates seamlessly with various IDEs like IntelliJ IDEA, reducing the process to a few straightforward steps.

C++, however, lacks a standardized package repository and even a standardized approach to building applications. While some developers prefer Visual Studio, others opt for CMake or alternative custom toolsets. Further complicating matters, certain commercial C++ libraries come in binary format, lacking a consistent integration method within the build process. Additionally, variations in build settings or compiler versions can lead to challenges when working with binary libraries.

Beginner-friendliness

The complexities of build and package management aren’t the sole reason behind C++’s steeper learning curve compared to Java. Debugging and safely utilizing C++ can be challenging for programmers unfamiliar with C, assembly languages, or low-level computer workings. C++ is akin to a power tool: highly capable but potentially dangerous if mishandled.

Java’s automatic memory management significantly enhances its accessibility. Java programmers are relieved from manual object memory deallocation, as the language handles this automatically.

The Decision: C++ or Java?

Having explored the intricacies of C++ and Java, we circle back to the initial question: Which language to choose? Even with a thorough understanding, there’s no universal answer.

Software engineers lacking familiarity with low-level programming concepts might favor Java when choosing between these two, except for real-time contexts like game development. Conversely, developers seeking to broaden their horizons might benefit more from C++.

However, the technical disparities between C++ and Java might play a minor role in the ultimate decision. Certain product types necessitate specific choices. If uncertainty persists, consulting a decision flowchart can be helpful, bearing in mind that it might ultimately point towards a third language.