Return type

In computer programming, the return type (or result type) defines and constrains the data type of the value returned from a subroutine or method.[1] In many programming languages (especially statically-typed programming languages such as C, C++, Java) the return type must be explicitly specified when declaring a function.

In the Java example:

public void setShuma(int n1, int n2) {
    Shuma = n1 + n2
}

public int getShuma() {
    return Shuma;
}

the return type is int. The program can therefore rely on the method returning a value of type int. Various mechanisms are used for the case where a subroutine does not return any value, e.g., a return type of void is used in some programming languages:

public void returnNothing()

Returning a value from a method

A method returns to the code that invoked it when it completes all the statements in the method, reaches a return statement, or throws an exception, whichever occurs first.

You declare a method's return type in its method declaration. Within the body of the method, you use the return statement to return the value.

Any method declared void doesn't return a value. It does not need to contain a return statement, but it may do so. In such a case, a return statement can be used to branch out of a control flow block and exit the method and is simply used like this:

return;

If you try to return a value from a method that is declared void, you will get a compiler error.

Any method that is not declared void must contain a return statement with a corresponding return value, like this:

return returnValue;

The data type of the return value must match the method's declared return type; you can't return an integer value from a method declared to return a boolean.

The getArea() method in the Rectangle Rectangle class that was discussed in the sections on objects returns an integer:

    // A method for computing the area of the rectangle
    public int getArea() {
        return width * height;
    }

This method returns the integer that the expression width * height evaluates to.

The getArea method returns a primitive type. A method can also return a reference type. For example, in a program to manipulate Bicycle objects, we might have a method like this:

    public Bicycle seeWhosFastest(Bicycle myBike, Bicycle yourBike,
                                  Environment env) {
        Bicycle fastest;
        // Code to calculate which bike is 
        // faster, given each bike's gear 
        // and cadence and given the 
        // environment (terrain and wind)
        return fastest;
    }
gollark: You can't stop people from misusing systems. The entire point of courts and such is that people don't act in good faith all the time.
gollark: Not that anyone actually unironically uses them.
gollark: In CS, we have a few examples of *provably* secure systems.
gollark: For example, if the court system was terrible and just asked the defendant whether they had broken the law and trusted them to be right, that would obviously be nonrobust.
gollark: No. There are robust systems and less robust ones.

References
  1. Kernighan, Brian W.; Ritchie, Dennis M. (1988). The C Programming Language (2nd ed.). Prentice Hall. ISBN 0-13-110362-8.
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