User-Defined Methods - Questions & Answers

EXERCISE

Part A : Objective Type Questions

1. The header is divided into return type, method name and the parameter list and is called as the prototype of the method.
(a) exception list    (b) prototype    (c) header    (d) signature

2. The list of parameters along with their data types is called the method signature.
(a) exception list    (b) prototype    (c) header    (d) signature

3. The void type is used if the method does not return any value.
(a) void    (b) null    (c) zero    (d) leave blank

4. Local variables are those variables that are defined within a method or a block and accessed only within the particular function or block.
(a) Global variables    (b) Local variables    (c) Instance variables    (d) Class variables

5. The parameters passed on the method call are called actual parameters.
(a) actual    (b) formal    (c) global    (d) local

6. Both a and b are those functions that only return the state of an object and does not make any changes to the current state.
(a) Pure functions    (b) Accessor functions    (c) Both a and b    (d) None of these

7. When the parameters passed are of array or class types, it is known as call by reference.
(a) call by value    (b) call by reference    (c) call by address    (d) none of these

8. A function can return maximum one value to the called function.
(a) any    (b) one    (c) zero    (d) none of these

9. When more than one method with the same name exists in the same program with different signatures, this is called method overloading.
(a) underloading    (b) overhauling    (c) overloading    (d) all of these

10. The method call in which the data in actual arguments and formal parameters remains same is known as call by reference.
(a) call by value    (b) pure function    (c) call by reference    (d) impure function

11. Impure methods are also known as Mutator functions.
(a) Accessor    (b) Mutator    (c) Overloading    (d) none of these

12. In Java a class is the basis of all computation.
(a) method    (b) constructor    (c) class    (d) object

13. When primitive data is passed through method call, is known as call by value.
(a) call by value    (b) call by reference    (c) call by address    (d) none of these

Part B : Solved Questions

1. What are two ways of invoking functions?
There are two ways of invoking functions :
Call by Value : When primitive data types are passed as an argument during function call, it is known as call by value. Any change made to the formal parameters will not affect or change the actual parameters.
Call by Reference : When an array or objects are passed as an argument during function call, it is known as call by reference. Any change made to the formal parameters will automatically change the value of the actual parameters.

2. Give the prototype of a function check which receives a character ch and an integer n and returns true or false.
boolean check (char ch, int n)

3. Name the keyword that causes the control to transfer back to the method call.
return

4. What do you understand by the term prototype? What is the need of it?
The header of a method with return type, method name and the parameter list is called the prototype of the method. Using the method prototype, the compiler checks the method during the invocation and compilation, whether the number and type of parameters are proper or not. If the number of parameters are not proper, an error message will be displayed by the compiler.

5. Define the terms pure and impure functions.
Pure functions are those functions that only return the state of an object and does not make any changes to the current state. They are also called Accessor Methods.
Impure functions are those functions that change the value of one or more fields or data members each time they are called. They are also called Mutator Methods.

6. Define the term function overloading. Give a program with functions to calculate area to explain it.
When more than one function with the same name exist in the same class with different signatures, this is called function overloading.
Example:
// Program to demonstrate Function overloading.
public class AreaCalculator
{
    float CalculateArea(float r)
        // area of circle
    {
        System.out.print("Area of Circle - ");
        float ar=22/7*r*r;
        return ar;
    }

    int CalculateArea (int l, int b)
        //area of rectangle
    {
        System.out.print("Area of Rectangle - ");
        return l*b;
    }
}

(i)
(a) What is the return type of method test()
(b) What will be the output if n = 12 is given.
(a) void
(b) 1 2 4 6 12

(ii) public class test
{
    public boolean result (int x)
    {
        if (x >= 0)
            return true;
        else
            return false;
    }
}
What will be the method result return, if
(a) x = -10
(b) x = +10
(c) return type of method
(d) signature type
(a) false
(b) true
(c) boolean
(d) one variable of type int

(iii) public class Demo
{
    int a, b;
    Demo()
    {
        a = 0;
        b = 0;
    }
    public int compare (int p, int q)
    {
        a = p;
        b = q;
        if (a>b)
            return a;
        else
            return b;
    }
    public static void main(String args[])
    {
        Scanner sc = new Scanner(System.in);
        int x, y, max;
        System.out.println("enter x");
        x = sc.nextInt(); // say x = 51
        System.out.println("enter y");
        y = sc.nextInt(); // say y = 50
        Demo ob1 = new Demo();
        max = ob1.compare(x, y);
        System.out.println("Maximum number is = " + max);
    }
}
(a) The Actual Arguments :
(b) The Formal Parameters :
(c) Return type of compare() :
(d) Method calling statement :
(e) Output : Maximum number is :
(a) x, y
(b) p, q
(c) int
(d) max = ob1.compare(x, y);
(e) 51