Java to C++: Conversion of basic concepts and syntax

Converting Java code to C++ code is a mapping between languages. Although both are object-oriented programming languages, there are obvious differences in some programming concepts and grammatical rules. In this article, we mainly conduct in-depth analysis and example demonstrations from aspects such as objects and classes, memory management, and exception handling.

1. Objects and classes

In Java and C++, classes are blueprints and templates for objects. However, Java is completely object-oriented and does not support global functions and global variables. In contrast, C++ is multi-paradigm and supports global functions and global variables.

// Java
class HelloWorld {
    public static void main(String[] args) {
        System.out.println("Hello, World!");
    }
}

// C++
#include <iostream>

using namespace std;

int main() {
    cout << "Hello, World!" << endl;
    return 0;
}

In addition, all class member functions in Java implicitly carry a self reference pointing to the current class object, but C++ requires an explicit declaration.

2. Memory management

Java has an automatic memory management mechanism, but C++ programmers need to be responsible for their own memory management. In Java, the garbage collector automatically cleans up memory that is no longer used, while in C++, programmers must manually release the memory they have applied for, otherwise memory leaks will occur.

// Java
public class Main {
    public static void main(String[] args) {
        int[] arr = new int[10];
        // No need to free memory in Java
    }
}

// C++
int main() {
    int* arr = new int[10];
    delete[] arr; // Don't forget to free memory in C++
    return 0;
}

3. Exception handling

Both Java and C++ support exception handling, but their implementations are slightly different. In Java, an exception is an object used to represent errors or other abnormal conditions. In C++, an exception can be any expression.

// Java
public class Main {
    public static void main(String[] args) {
        try {
            int[] myNumbers = {1, 2, 3};
            System.out.println(myNumbers[10]);
        } catch (ArrayIndexOutOfBoundsException e) {
            System.out.println("ArrayIndexOutOfBoundsException caught");
        }
    }
}

// C++
#include <iostream>
#include <exception>

using namespace std;

int main() {
    try {
        int myNumbers[3] = {1, 2, 3};
        cout << myNumbers[10];
    } catch (exception& e) {
        cout << "Array out of bound exception caught" << endl;
    }
    return 0;
}

With the above code, we can better understand how to convert Java code to C++ code. In real applications, depending on the complexity of the program and the amount of code, the language conversion effort may become more complex.