List Handling in Java vs C# vs C++ – A Deep Comparison

In every software project, managing collections of data is a fundamental need. Lists (dynamic arrays) that grow and shrink at runtime are among the most common structures in any application, from simple TODO apps to complex trading systems.

Lists (or dynamic arrays) are fundamental to every language, but their implementation and behavior vary significantly across Java, C#, and C++. This comparison provides a full view of how these languages deal with list-like structures, from syntax to internals.

Why Compare Java, C#, and C++ for List Handling?

Java, C# and C++ are among the most widely used languages in the world for both academic and professional development. Each language has its own set of strengths

• Java is platform-independent, heavily used in enterprise applications.
• C# is known for rapid development with rich .NET ecosystem integrations.
• C++ offers low-level control, ideal for performance-critical systems.

Understanding how each handles list-like structures helps developers write more optimized, idiomatic and maintainable code.

Q1. What is the difference between ArrayList in Java and List<T> in C#?

Both ArrayList in Java and List<T> in C# are dynamic arrays that resize automatically. However

• ArrayList in Java is a raw type that requires boxing/unboxing for primitives. For type safety, use List<Integer> with generics.
• List<T> in C# is always generic and type-safe, avoiding unnecessary boxing for value types like int.
• Use Java generics to ensure type safety, similar to how C# enforces it by design.

Q2. Is std::vector in C++ faster than Java's ArrayList and C#'s List<T>?

Yes, std::vector is generally faster than Java’s ArrayList and C#’s List<T> for raw performance and low-level operations, because

• No Garbage Collection: C++ doesn’t use garbage collection like Java and C#. This means memory is released immediately when it's no longer needed, avoiding unpredictable GC pauses that might slow down performance in managed languages.
• Minimal Runtime Overhead : Unlike Java and C#, std::vector does not perform runtime bounds checking by default, which removes an extra layer of overhead and speeds up access operations. (Though you can enable checks manually using .at().)
• Direct Memory Control: With std::vector, developers have more control over memory usage. You can use functions like reserve(), shrink_to_fit(), and custom allocators to optimize memory allocation, which can lead to better performance in tight loops and large-scale operations.

However, this performance advantage comes with trade-offs

Q3. Are these list structures thread-safe by default?

No. All three list implementations are not thread-safe by default. If you want thread safety

• Java: Use Collections.synchronizedList() or CopyOnWriteArrayList.
• C#: Use ConcurrentBag, BlockingCollection or ImmutableList<T>.
• C++: Use std::mutex, std::lock_guard or tbb::concurrent_vector.

Note : Always wrap or replace list structures when working in multithreaded environments.

Q4. How can I improve performance when using lists in high-traffic systems?

Here are some language-specific tips to improve performance when using lists in high-traffic systems

• Java: Use ensureCapacity() if you know the list size ahead of time to reduce resizing.
• C#: Set .Capacity or initialize with new List<T>(capacity).
• C++: Use reserve(n) early and avoid frequent reallocations.

Note : Preallocating memory is key to maintaining high throughput in performance-sensitive systems.

Q5. What happens when I access an invalid index in a list?

• Java: Throws IndexOutOfBoundsException.
• C#: Throws ArgumentOutOfRangeException.
• C++: Undefined behavior (may crash, corrupt memory or return garbage).

Tip : In C++, prefer .at(index) for bounds checking (throws std::out_of_range).

Q6. Can I store objects in these lists?

Yes. All three support storing user-defined or reference types

• Java: List<MyClass> list = new ArrayList<>();
• C#: List<MyClass> list = new List<MyClass>();
• C++: std::vector<MyClass> list;

Tip : Make sure to implement proper copy/move constructors in C++ to avoid unnecessary overhead.

Q7. Which List Implementation Is Best for Sorting and Searching in Java, C# and C++?

All three languages Java, C# and C++ offer efficient built-in support for sorting and searching in their list implementations. Here's how they compare and when to use which

Q9. How do I clone a list in each Java, c# and c++?

• Java: List<Integer> copy = new ArrayList<>(originalList);
• C#: List<int> copy = new List<int>(originalList);
• C++: std::vector<int> copy = original; (deep copy)

All copies above are shallow copies for reference types objects themselves are not duplicated unless manually done.

Q10. Which language provides the best support for functional programming with lists?

• C# offers the most concise, expressive, and feature-rich experience with LINQ — unmatched in flexibility
• C#: LINQ (list.Where(...).Select(...))
• Java comes in strong with Streams, though it’s generally more verbose and slightly heavier at runtime.
• Java: Streams (list.stream().filter(...).collect(...))
• C++, with Ranges, provides high-performance, zero-overhead pipelines — still evolving in expressiveness and library support.
• C++: Ranges (C++20): std::views::filter, std::ranges::sort

In short: C# wins in expressiveness, Java is powerful but verbose, C++ offers performance-driven pipelines with evolving ergonomics.

11. Explain Custom Sorting in Java with Example

In Java, you can perform custom sorting on lists using

• Comparator interface
• Lambda expressions (Java 8+)
• Method references (Java 8+)

public class Person {
    String name;
    int age;
    public Person(String name, int age) {
        this.name = name;
        this.age = age;
    }
    @Override
    public String toString() {
        return name + " (" + age + ")";
    }
    public int getAge() {
        return age;
    }
    public String getName() {
        return name;
    }
}

import java.util.*;

public class SortExample {
    public static void main(String[] args) {
        List<Person> people = new ArrayList<>();
        people.add(new Person("Alice", 30));
        people.add(new Person("Bob", 25));
        people.add(new Person("Charlie", 35));
        // Sort by age (ascending)
        people.sort((p1, p2) -> p1.age - p2.age);
        // Print sorted list
        System.out.println("Sorted by age:");
        people.forEach(System.out::println);
    }
}

// Sort by name alphabetically
people.sort(Comparator.comparing(Person::getName));

System.out.println("Sorted by name:");
people.forEach(System.out::println);

// Sort by age descending
people.sort((p1, p2) -> p2.age - p1.age);

// Or using Comparator:
people.sort(Comparator.comparing(Person::getAge).reversed());

12. Explain Custom Sorting in C# with Example

In C#, you can perform custom sorting on lists using

• Lambda expressions
• IComparer<T> implementation
• Comparison<T> delegate

public class Person
{
    public string Name { get; set; }
    public int Age { get; set; }

    public override string ToString() => $"{Name} ({Age})";
}

using System;
using System.Collections.Generic;

class Program
{
    static void Main()
    {
        List<Person> people = new List<Person>
        {
            new Person { Name = "Alice", Age = 30 },
            new Person { Name = "Bob", Age = 25 },
            new Person { Name = "Charlie", Age = 35 }
        };

        // Sort by Age ascending
        people.Sort((p1, p2) => p1.Age.CompareTo(p2.Age));
        Console.WriteLine("Sorted by Age:");
        people.ForEach(p => Console.WriteLine(p));
    }
}

// Sort by Name alphabetically
people.Sort((p1, p2) => p1.Name.CompareTo(p2.Name));

Console.WriteLine("Sorted by Name:");
people.ForEach(p => Console.WriteLine(p));

// Sort by Age descending
people.Sort((p1, p2) => p2.Age.CompareTo(p1.Age));

public class AgeDescendingComparer : IComparer<Person>
{
    public int Compare(Person x, Person y)
    {
        return y.Age.CompareTo(x.Age);
    }
}

// Usage:
people.Sort(new AgeDescendingComparer());

people.Sort((p1, p2) => {
    int ageCompare = p1.Age.CompareTo(p2.Age);
    return ageCompare != 0 ? ageCompare : p1.Name.CompareTo(p2.Name);
});

Comparison<Person> ageComparison = delegate(Person x, Person y)
{
    return x.Age.CompareTo(y.Age);
};

// Sort using the Comparison<T> delegate
people.Sort(ageComparison);

Console.WriteLine("Sorted by Age:");
people.ForEach(p => Console.WriteLine(p));

13. Explain Custom Sorting in C++ with example

In C++, you can customize sorting behavior using

• Lambda expressions
• Function pointers
• Functor (function objects)

The standard sorting function is std::sort() from <algorithm>, which works on containers like std::vector.

#include <iostream>
#include <vector>
#include <algorithm>

struct Person {
    std::string name;
    int age;

    void print() const {
        std::cout << name << " (" << age << ")\n";
    }
};

int main() {
    std::vector<Person> people = {
        {"Alice", 30},
        {"Bob", 25},
        {"Charlie", 35}
    };
    // Sort by age (ascending)
    std::sort(people.begin(), people.end(), [](const Person&amp; a, const Person&amp; b) {
        return a.age < b.age;
    });
    std::cout << "Sorted by age:\n";
    for (const auto&amp; person : people) person.print();
    return 0;
}

// Sort by name
std::sort(people.begin(), people.end(), [](const Person& a, const Person& b) {
    return a.name < b.name;
});

std::sort(people.begin(), people.end(), [](const Person& a, const Person& b) {
    return a.age > b.age;
});

std::sort(people.begin(), people.end(), [](const Person& a, const Person& b) {
    if (a.age == b.age) {
        return a.name < b.name;
    }
    return a.age < b.age;
});

bool compareByAge(const Person& a, const Person& b) {
    return a.age < b.age;
}

// Usage
std::sort(people.begin(), people.end(), compareByAge);

struct CompareByName {
    bool operator()(const Person& a, const Person& b) const {
        return a.name < b.name;
    }
};

// Usage
std::sort(people.begin(), people.end(), CompareByName());

14. What’s the impact of equals() vs == in these lists?

It comes down to comparing values vs references (or memory addresses).

• Java (ArrayList)
  • equals() compares the contents of two lists — same size and same elements in order.
  • == checks if both lists are the same object in memory (i.e. same reference).
  • So, use list1.equals(list2) when you want to check if two ArrayLists contain the same values.
• C# (List<T>)
  • == depends on operator overloading, which by default compares references — not values.
  • To compare values, use list1.SequenceEqual(list2) which checks if both lists have the same elements in order.
• C++ (std::vector)
  • In modern C++ (C++20 and even earlier), == compares vectors element by element by default.
  • Alternatively, you can use std::equal() for manual or more flexible comparisons.
  • If you're working with pointers, remember: == compares the addresses, not the pointed-to values.

Tip : Always use value-based comparison methods (equals(), SequenceEqual(), std::equal()) when checking if two lists/vectors contain the same elements, this ensures accurate, reliable results across all languages.

15. How do I merge two lists?

Merging lists efficiently is essential for algorithms that combine datasets or transform collections. Here is how you can merge lists

• Java: newList.addAll(otherList) merges elements.
• C#: list.AddRange(otherList).
• C++: vec.insert(vec.end(), otherVec.begin(), otherVec.end()).