Java Programs

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Short Questions/Answers - Java Programs

Question 1
Choose the correct answers to the questions from the given options.
(Do not copy the questions, write the correct answers only)

(i)

Consider the above picture and choose the correct statement from the following:
(a) Polygon is the object and the pictures are classes.
(b) Both polygon and pictures are classes.
(c) Polygon is the class and the pictures are objects.
(d) Both polygon and the pictures are objects.

(ii) int x = 98; char ch = (char)x; What is the value in ch?
(a) b
(b) A
(c) B
(d) 97

(iii) The output of the statement “CONCENTRATION”.indexOf(‘T’) is:
(a) 9
(b) 7
(c) 6
(d) (-1)

(iv) The access specifier that gives least accessibility is:
(a) package
(b) public
(c) protected
(d) private

(v) The output of the statement “talent”.compareTo(“genius”) is:
(a) 11
(b) -11
(c) 0
(d) 13

(vi) Which of the following is an escape sequence character in Java?
(a) /n
(b) \t
(c) /t
(d) //n

(vii) if(a > b && b > c) then largest number is:
(a) b
(b) c
(c) a
(d) wrong expression

(viii) What is the output of Math.ceil(5.4) + Math.ceil(4.5)?
(a) 10.0
(b) 11.0
(c) 12.0
(d) 9.0

(ix) What is the method to check whether a character is a letter or digit?
(a) isDigit(char)
(b) isLetterOrDigit()
(c) isLetterOrDigit(char)
(d) isLETTERorDIGIT(char)

(x) The extension of a Java source code file is:
(a) exe
(b) obj
(c) jvm
(d) java

(xi) The number of bytes occupied by a character array of four rows and three columns are:
(a) 12
(b) 24
(c) 96
(d) 48

(xii) Which of the following data type cannot be used with switch case construct?
(a) int
(b) char
(c) String
(d) double

(xiii) Which of the following are entry-controlled loops?
1. for
2. while
3. do..while
4. switch

(a) only 1
(b) 1 and 2
(c) 1 and 3
(d) 3 and 4

(xiv) Method which reverses a given number is:
(a) Impure method
(b) Pure method
(c) Constructor
(d) Destructor

(xv) If the name of the class is “Yellow”, what can be the possible name for its constructors?
(a) yellow
(b) YELLOW
(c) Yell
(d) Yellow

(xvi) Invoking a method by passing the objects of a class is termed as:
(a) Call by reference
(b) Call by value
(c) Call by method
(d) Call by constructor

(xvii) The correct statement to create an object named mango of class fruit:
(a) Fruit Mango = new fruit();
(b) fruit mango = new fruit();
(c) Mango fruit = new Mango();
(d) fruit mango = new mango();

(xviii) Assertion (A): Static method can access static and instance variables.
Reason (R): Static variable can be accessed only by static method.
(a) Assertion and Reason both are correct.
(b) Assertion is true and Reason is false
(c) Assertion is false and Reason is true
(d) Assertion and Reason both are false

(xix) What is the output of the Java code given below?
String color[] = {“Blue”, “Red”, “Violet”};
System.out.println(color[2].length());
(a) 6
(b) 5
(c) 3
(d) 2

(xx) Which of the following mathematical methods returns only an integer?
(a) Math.ceil(n)
(b) Math.sqrt(n)
(c) Math.floor(n)
(d) Math.round(n)

Question 2

(i) Write Java expression for:
OUTPUT: Math.abs(a + b) / Math.sqrt(a * a + b * b)

(ii) Evaluate the expression when x is 4:
x += x++ * ++x % 2;
x = x + (x++ * ++x % 2);
x = 4 + (4 * 6 % 2)
x = 4 + (24 % 2)
x = 4 + 0
x = 4

(iii) Rewrite the following do while program segment using for:
x = 10; y = 20;
do{
    x++;
   y++;
  }while(x <= 20);
System.out.println(x * y);

x = 10; y = 20;
for(;;){
x++;
y++;
if(x > 20)
break;
}
System.out.println(x * y);

(iv) Give the output of the following program segment. How many times is the loop executed?
for(x = 10; x > 20; x++)
 System.out.println(x);
 System.out.println(x * 2);

OUTPUT: 20
The loop executes 0 times.

(v) String s1 = “45.50”; String s2 = “54.50”;
double d1 = Double.parseDouble(s1);
double d2 = Double.parseDouble(s2);
int x = (int)(d1 + d2);

What is the value of x?

OUTPUT:
x = 100

(vi) Consider the following two-dimensional array and answer the questions given below:
int x[][] = {{4, 3, 2}, {7, 8, 2}, {8, 3, 10}, {1, 2, 9}};
(a) What is the order of the array?
(b) What is the value of x[0][0] + x[2][2]?

OUTPUT:
Order is 4 × 3.
x[0][0] + x[2][2] = 4 + 10 = 14

(vii) Differentiate between boxing and unboxing.

OUTPUT:

Autoboxing/boxing is the automatic conversion of primitive data types to their corresponding wrapper classes when needed. Unboxing is the automatic conversion of wrapper class objects to their corresponding primitive data types when needed.

(viii) The following code to compare two strings is compiled, the following syntax error was displayed – incompatible types – int cannot be converted to boolean. Identify the statement which has the error and write the correct statement. Give the output of the program segment.

void calculate(){

    String a = "KING", b = "KINGDOM";

    boolean x = a.compareTo(b);

    System.out.println(x);

}

OUTPUT:

The error is in line: boolean x = a.compareTo(b);
The correct statement is: int x = a.compareTo(b);
The output is: -3

(ix) Consider the given program and answer the questions given below:

class temp{

    int a;

    temp(){

        a = 10;

    }

    temp(int z){

        a = z;

    }

    void print(){

        System.out.println(a);

    }

    void main(){

        temp t = new temp();

        temp x = new temp(30);

        t.print();

        x.print();

    }

}

(a) What concept of OOPs is depicted in the above program with two constructors?
(b) What is the output of the method main()?

OUTPUT:
(a) Due to constructor overloading, the OOP Polymorphism is depicted.
(b) The output is:
10
30

(x) Primitive data types are built-in data types which are a part of the wrapper classes. These wrapper classes are encapsulated in the java.lang package. Non-primitive data types like Scanner class are a part of the utility package for which an object needs to be created.

(a) To which package the Character and Boolean classes belong?
(b) Write the statement to access the Scanner class in the program.

OUTPUT:
(a) The Character and Boolean classes belong to the java.lang package.
(b) The statement to access the Scanner class is: import java.util.Scanner;

class Overload{
    public static void display(){
        for(int i = 1; i <= 3; i++){
            int value = 1;
            for(int j = 1; j <= 5; j++){
                System.out.print(value + " ");
                if(value == 1)
                    value = 2;
                else
                    value = 1;
            }
            System.out.println();
        }
    }
    public static void display(int n, int m){
        if(m > n){
            int q = m / n;
            System.out.println("Quotient = " + q);
        }
        else{
            int sum = 2 * n + 3 * m;
            System.out.println("Sum = " + sum);
        }
    }
    public static double display(double a, double b, double c){
        double p = (a + b) / c;
        double q = a + b + c;
        double z = p * q;
        System.out.println("z = " + z);
        return z;
    }
}