cpp_vs_java.md

• Function definition -

  In C++, function declaration should be done, before its use. Or else, define entirely before its use in the main function
  E.g.

  void foo(int); // Prototype declaration of foo, seen by main
                 // Must specify return type, name, and argument list types
  int main()
  {
    foo(2); // OK: foo is known, called even though its body is not yet defined
  }
  void foo(int x) //Must match the prototype
  {
    // Define body of foo here
  }

  In Java, there is no such rule. Define anywhere.

• Pointers & Reference

  In C++, define Reference (using the object and putting own label) like this:

  Box& b;  // defining a reference like Java
  b.setLength(3.5);
  b.setBreadth(5.6);
  b.setHeight(6.7);

  and Pointer (like a new stack in the memory) like this:

  Box* b = new Box(args);
  b->setLength(3.5);
  b->setBreadth(5.6);
  b->setHeight(6.7);

  In Java, no pointer only reference.

  Box b;
  b.setLength(3.5);
  b.setBreadth(5.6);
  b.setHeight(6.7);

• static use in functions

  C++:

  static (in function) saves the state. For more, click here

  #include <iostream>
  
  using namespace std;
  
  void func() {
      static int i = 0;
      cout << i;
      i++;
  }
  
  int main() {
      func();
      func();
      func();
  
      return 0;
  }

  Output:

  012
  

  Here, static means the function saves the previous state and runs from there on next call.

  Java:

  static has no such role.

  class Main {
      static void func() {
          /*static*/ int i = 0;
          System.out.println(i);
          i++;
      }
      public static void main(String[] args) {
          func();
          func();
          func();
      }
  }

  Output:

  0
  0
  0
  

  Here, use of static would give error.