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Java System.exit(0) vs C++ return 0

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  • Last Updated : 01 Sep, 2020
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Java and C++ are languages with different applications and design goals. C++ is an extension of procedural programming language C and Java relies on a Java virtual machine to be secure and highly portable. This leads them to many differences. In this article, we will see the difference between C++ return 0 and Java System.exit(0). Before getting into the differences, let us first understand what each of them actually means.

C++ return 0

  • In Standard C++, it is recommended to create a main() function with a return type.
  • So, the main() function must return an integer value and this integer value is usually the value that will be passed back to the operating system.

In stdlib.h the macros EXIT_SUCCESS and EXIT_FAILURE are defined like this :

#define EXIT_SUCCESS    0
#define EXIT_FAILURE    1
  • return 0 –> successful termination.
  • return 1 or any other non-zero value –> unsuccessful termination.
  • Returning different values like return 1 or return -1 or any other non-zero value means that program is returning error.

C++




#include <iostream>
  
using namespace std;
  
int main()
{
    int num1, num2;
    cin >> num1 >> num2;
    cout << num1 + num2;
  
    return 0;
}

Input:
54
4


Output:
58

Java System.exit(0)

The first thing to take into consideration is that the main function in java has a return type void.

  • In Java, you can’t return the exit code, because it’s a void function. So, if you want to explicitly specify an exit code, you have to use System.exit() method.
  • The java.lang.System.exit() method exits the current program by terminating running Java virtual machine.

Declaration for java.lang.System.exit() method:

public static void exit(int status)
exit(0) -->successful termination.
exit(1) or exit(-1) or any other non-zero value –-> unsuccessful termination.

Java




import java.io.*;
  
class GFG {
    public static void main (String[] args) {
        System.out.println("GeeksForGeeks");
    }
}

Output:
GeeksforGeeks

Note: The work of both return 0 and System.exit(0) is the same as the difference in the return type of the main() functions.  

The following table describes the differences:

SR.NOC++ Return 0Java System.exit(0) 
1.The main() function in C++ has a return type. Hence, every main method in C++ should return any value.The main() method in java is of void return type. Hence, main method should not return any value.
2.In a C++ program return 0 statement is optional: the compiler automatically adds a return 0 in a program implicitly.In Java, there is no special requirement to call System.exit(0) or add it explicitly.
3.It is a keyword which is used to return some value, so it does not need any declaration.It needs only return keyword with value or variables.   

Declaration for java.lang.System.exit() method:

public static void exit(int status)

4.Generally, return 0 is used to return exit code to the operating system.If we want to explicitly specify an exit code to the operating system, we have to use System.exit().
5.Using return 0 in C++ programs is considered a good practice.Using System.exit(0) is avoided in practice because we have our main() method with void return type.

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