Question 1

Question 1What is a java package? Give an example.

Accepted Answer

A package is a named collection of Java classes that are grouped on the basis of their functionality. For example, java.util.

Question 2

Question 2Explain the use of import statement with an example.

Accepted Answer

import statement is used to import built-in and user-defined packages and classes into our Java program. For example, we can import all the classes present in the java.util package into our program using the below statement:import java.util.*;

Question 3

Question 3Explain the statement, "a well-documented code is as important as the correctly working code".

Accepted Answer

Writing fully commented code is a good programming style. The primary purpose of comments is to document the code so that even a layman can understand the purpose of the written code. Hence, a well-documented code is as important as the correctly working code.

Question 4

Question 4How can you write single line comments in Java?

Accepted Answer

Single line comments in Java can be written in the below two ways:Using Single line comments style — Single line comment begin with a double slash (//) and continues till the end of the line. For example:// Single line comment exampleUsing Multi line comments style — In this style, comments start with the initiating slash-asterisk (/*) and ends with the terminating asterisk-slash(*/). For example:/* Single line comment using multi line comment style */

Question 5

Question 5Explain data input technique in a program using the Scanner class.

Accepted Answer

The data entered by the user through the keyboard is provided to our Java program with the help of standard input stream that is specified as System.in in the program. We connect our Scanner class to this stream while creating its object. The input received by Scanner class is broken into tokens using a delimiter pattern. The default delimiter is whitespace. Scanner class provides various next methods to read these tokens from the stream. The different next methods provided by Scanner class are next(), nextShort(), nextInt(), nextLong(), nextFloat(), nextDouble(), nextLine(), next().charAt(0).

Question 6

Question 6Distinguish between the following:i. next() and nextLine()

Accepted Answer

next()nextLine()It reads the input only till the next complete token until the delimiter is encountered.It reads the input till the end of line so it can read a full sentence including spaces.It places the cursor in the same line after reading the input.It places the cursor in the next line after reading the input.ii. next() and next().charAt(0)next()next().charAt(0)It reads the input only till the next complete token until the delimiter is encountered.It reads the complete token and then the first character is returned using the charAt(0) method.It returns the read data as a String value.It returns the read data as a char value.iii. next() and hasNext()next()hasNext()It reads the input till the next complete token until the delimiter is encountered.It checks if the Scanner has another token in its input.It returns a String value.It returns a boolean value.iv. hasNext() and hasNextLine()hasNext()hasNextLine()Returns true if the Scanner object has another token in its input.Returns true if there is another line in the input of the Scanner object.

Question 7

Question 7What are delimiters? Which is the default delimiter used in the Scanner class?

Accepted Answer

A delimiter is a sequence of one or more characters that separates two tokens. The default delimiter is a whitespace.

Question 8

Question 8What are errors in a program?

Accepted Answer

Errors are mistakes in a program that prevents it from its normal working. They are often referred to as bugs. Errors are classified into three categories — Syntax Errors, Runtime Errors and Logical Errors.

Question 9

Question 9Explain the following terms, giving an example of each.i. Syntax error

Accepted Answer

Syntax Errors are the errors that occur when we violate the rules of writing the statements of the programming language. These errors are reported by the compiler and they prevent the program from executing. For example, the following statement will give an error as we missed terminating it with a semicolon:int sumii. Runtime errorErrors that occur during the execution of the program primarily due to the state of the program which can only be resolved at runtime are called Run Time errors.Consider the below example:import java.util.Scanner;

class RunTimeError
{
    public static void main(String args[]) {
        Scanner in = new Scanner(System.in);
        System.out.print("Enter a number: ");
        int n = in.nextInt();
        int result = 100 / n;
        System.out.println("Result = " + result);
    }
}This program will work fine for all non-zero values of n entered by the user. When the user enters zero, a run-time error will occur as the program is trying to perform an illegal mathematical operation of division by 0. When we are compiling the program, we cannot say if division by 0 error will occur or not. It entirely depends on the state of the program at run-time.iii. Logical errorWhen a program compiles and runs without errors but produces an incorrect result, this type of error is known as logical error. It is caused by a mistake in the program logic which is often due to human error. Logical errors are not caught by the compiler. Consider the below example for finding the perimeter of a rectangle with length 2 and breadth 4:class RectanglePerimeter
{
    public static void main(String args[]) {
        int l = 2, b = 4;
        double perimeter = 2 * (l * b);    //This line has a logical error
        System.out.println("Perimeter = " + perimeter);
    }
}OutputPerimeter = 16
The program gives an incorrect perimeter value of 16 as the output due to a logical error. The correct perimeter is 12. We have written the formula of calculating perimeter incorrectly in the line double perimeter = 2 * (l * b);. The correct line should be double perimeter = 2 * (l + b);.

Question 10

Question 10A program has compiled successfully without any errors. Does this mean the program is error free? Explain.

Accepted Answer

Successful compilation of the program only ensures that there are no syntax errors. Runtime and logical errors can still be there in the program so we cannot say that the program is error free. Only after comprehensive testing of the program, we can say that the program is error free.

Question 11

Question 11Write a program in Java that uses 'input using initialisation' to calculate the Simple Interest and the Total Amount with the given values:i. Principle Amount = Rs. 20000ii. Rate = 8.9%iii. Time = 3 years

Accepted Answer

public class KboatInterest
{
    public static void main(String args[]) {
        int p = 20000;
        double r = 8.9;
        int t = 3;
        double si = p * r * t / 100.0;
        double amt = p + si;
        System.out.println("Simple Interest = " + si);
        System.out.println("Total Amount = " + amt);
    }
}Output

Question 12

Question 12Write a program in Java that accepts the seconds as input and converts them into the corresponding number of hours, minutes and seconds. A sample output is shown below:Enter Total Seconds:
5000
1 Hour(s) 23 Minute(s) 20 Second(s)

Accepted Answer

import java.util.Scanner;

public class KboatTimeConvert
{
    public static void main(String args[]) {
        Scanner in = new Scanner(System.in);
        System.out.print("Enter time in seconds: ");
        long secs = in.nextLong();
        long hrs = secs / 3600;
        secs %= 3600;
        long mins = secs / 60;
        secs %= 60;
        System.out.println(hrs + " Hour(s) " + mins 
            + " Minute(s) " + secs + " Second(s)");
        in.close();
    }
}Output

Question 13

Question 13Write a program in java to input the temperature in Fahrenheit, convert it into Celsius and display the value in the Terminal window. A sample output is displayed below:Enter temperature in Fahrenheit
176
176.0 degree Fahrenheit = 80.0 degree Celsius

Accepted Answer

import java.util.Scanner;

public class KboatTemperature
{
    public static void main(String args[]) {
        Scanner in = new Scanner(System.in);
        System.out.println("Enter temperature in Fahrenheit: ");
        double f = in.nextDouble();
        double c = (f - 32) * 5.0 / 9.0;
        System.out.println(f + " degree Fahrenheit = " + c + " degree Celsius");
    }
}Output

Input in Java