Chapter 5

Input In Java
Class 9 - APC Understanding Computer Applications with
BlueJ

Name the following

Question 1

a package needed to import scanner class

java.util

Question 2

a method that accepts a character through scanner object

charAt()

Question 3

a package needed to import Stream Reader Class

java.io

Question 4

a method to accept an exponential value through scanner object

nextDouble()

Question 5

a method that accepts an integer token through scanner object

nextInt()

Write down the syntax with reference to Java Programming

Question 1

to accept an integral value 'p' through Stream Class

InputStreamReader read = new InputStreamReader(System.in);
BufferedReader in = new BufferedReader(read);
int p = Integer.parseInt(in.readLine());

Question 2

to accept a fractional value (float) 'm' through Scanner Class

Scanner in = new Scanner(System.in);

float m = in.nextFloat();

Question 3

to accept a character 'd' through Stream Class

InputStreamReader read = new InputStreamReader(System.in);

BufferedReader in = new BufferedReader(read);
char d = (char)in.read();

Question 4

to accept a fraction value 'n' in double data type through Stream Class

InputStreamReader read = new InputStreamReader(System.in);

BufferedReader in = new BufferedReader(read);
double n = Double.parseDouble(in.readLine());

Question 5

to accept a word 'wd' through Stream Class

InputStreamReader read = new InputStreamReader(System.in);

BufferedReader in = new BufferedReader(read);
String wd = in.readLine();

Question 6

to create a scanner object

Scanner in = new Scanner(System.in);

Differentiate between the following

Question 1
nextInt( ) and nextFloat( ) methods

nextInt( ) nextFloat( )

Scans the next token of input as an int Scans the next token of input as a float

Question 2

Syntax and logical errors

Syntax Errors Logical Errors

Syntax Errors occur when we violate the rules of writing the Logical Errors occur due to our mistakes in
statements of the programming language. programming logic.

Program compiles and executes but doesn't gi

Program fails to compile and execute.
the desired output.

Logic errors need to be found and corrected b

Syntax Errors are caught by the compiler.
people working on the program.

Answer the following

Question 1

What do you mean by scanner class?

Scanner class is used to get user input. It is present in java.util package.

Question 2

What are the different ways to give inputs in a Java Program?

Java provides the following ways to give input in a program:

1. Using Function Argument.

2. Using InputStreamReader class.
3. Using Scanner class.
4. Using Command Line Arguments.

Question 3
What is the use of the keyword import?
import keyword is used to import built-in and user-defined packages into our Java
program.

Question 4

What is a package? Give an example.

In Java, a package is used to group related classes. Packages are of 2 types:

1. Built-In packages — These are provided by Java API

2. User-Defined packages — These are created by the programmers to efficiently
structure their code.
java.util, java.lang are a couple of examples of built-in packages.

Question 5

What is the use of the keyword 'import' in Java programming?

import keyword is used to import built-in and user-defined packages into our Java
program.

Question 6

What is a compound statement? Give an example.

Two or more statements can be grouped together by enclosing them between opening and
closing curly braces. Such a group of statements is called a compound statement.

if (a < b) {

/*
* All statements within this set of braces
* form the compound statement
*/

System.out.println("a is less than b");

a = 10;
b = 20;
System.out.println("The value of a is " + a);
System.out.println("The value of b is " + b);

Question 7

Write down the syntax to input a character through scanner class with an example.

Syntax:
char <variable name> = <Scanner Object>.next().charAt(0);
Example:

Scanner in = new Scanner(System.in);

char ch = in.next().charAt(0);

Question 8

What do you understand by 'Run Time' error? Explain with an example

Errors 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.

Question 9

What are the different types of errors that take place during the execution of a program?
Logical errors and Run-Time errors occur during the execution of the program.

Question 10

Distinguish between:
(a) Testing and Debugging

Testing Debugging

In the process of Testing, we check if the program is working as In the process of Debugging, we correc
expected and find out the errors if it is not giving the expected
 Testing Debugging

output. errors that were found during testing.

(b) Syntax error and Logical error

Syntax Error Logical Error

Syntax Errors occur when we violate the rules of writing the Logical Errors occur due to our mistakes in
statements of the programming language. programming logic.

Program compiles and executes but doesn't g

Program fails to compile and execute.
the desired output.

Logical errors need to be found and corrected

Syntax Errors are caught by the compiler.
people working on the program.

Solutions to Unsolved Java Programs

Question 1
The time period of a Simple Pendulum is given by the formula:
T = 2π√(l/g)
Write a program to calculate the time period of a Simple Pendulum by
taking length and acceleration due to gravity (g) as inputs.
import java.util.Scanner;

public class KboatSimplePendulum

{
public static void main(String args[]) {
Scanner in = new Scanner(System.in);
System.out.print("Enter length: ");
double l = in.nextDouble();
System.out.print("Enter g: ");
double g = in.nextDouble();
double t = 2 * (22.0 / 7.0) * Math.sqrt(l/g);
System.out.println("T = " + t);
}
}

Output

Question 2
Write a program by using class 'Employee' to accept Basic Pay of an
employee. Calculate the allowances/deductions as given below.

Allowance / Deduction Rate

Dearness Allowance (DA) 30% of Basic Pay

House Rent Allowance (HRA) 15% of Basic Pay

Provident Fund (PF) 12.5% of Basic Pay

Finally, find and print the Gross and Net pay.

Gross Pay = Basic Pay + Dearness Allowance + House Rent Allowance
Net Pay = Gross Pay - Provident Fund
import java.util.Scanner;

public class Employee

{
public static void main(String args[]) {
Scanner in = new Scanner(System.in);
System.out.print("Enter Basic Pay: ");
double bp = in.nextDouble();
double da = 0.3 * bp;
double hra = 0.15 * bp;
double pf = 0.125 * bp;
double gp = bp + da + hra;
double np = gp - pf;
System.out.println("Gross Pay = " + gp);
System.out.println("Net Pay = " + np);
}
}
Output

Question 3
A shopkeeper offers 10% discount on the printed price of a Digital
Camera. However, a customer has to pay 6% GST on the remaining
amount. Write a program in Java to calculate the amount to be paid by
the customer taking printed price as an input.
import java.util.Scanner;

public class KboatCameraPrice

{
public static void main(String args[]) {
Scanner in = new Scanner(System.in);
System.out.println("Enter printed price of Digital Camera:");
double mrp = in.nextDouble();
double disc = mrp * 10 / 100.0;
double price = mrp - disc;
double gst = price * 6 / 100.0;
price += gst;
System.out.println("Amount to be paid: " + price);
}
}

Output

Question 4
A shopkeeper offers 30% discount on purchasing articles whereas the
other shopkeeper offers two successive discounts 20% and 10% for
purchasing the same articles. Write a program in Java to compute and
display the discounts.
Take the price of an article as the input.
import java.util.Scanner;

public class KboatDiscounts

{
public static void main(String args[]) {
Scanner in = new Scanner(System.in);
System.out.print("Enter price of article: ");
double price = in.nextDouble();

double d1 = price * 30 / 100.0;

double amt1 = price - d1;
System.out.println("30% discount = " + d1);
System.out.println("Amount after 30% discount = " + amt1);

double d2 = price * 20 / 100.0;

double amt2 = price - d2;
double d3 = amt2 * 10 / 100.0;
amt2 -= d3;
System.out.println("20% discount = " + d2);
System.out.println("10% discount = " + d3);
System.out.println("Amount after successive discounts = " +
amt2);
}
}

Output

Question 5
Mr. Agarwal invests certain sum at 5% per annum compound interest
for three years. Write a program in Java to calculate:
(a) the interest for the first year
(b) the interest for the second year
(c) the amount after three years.
Take sum as an input from the user.
Sample Input: Principal = ₹5000, Rate =10%, Time = 3 yrs
Sample Output: Interest for the first year: ₹500
Interest for the second year: ₹550
Interest for the third year: ₹605
import java.util.Scanner;
public class KboatCompoundInterest
{
public static void main(String args[]) {
Scanner in = new Scanner(System.in);
System.out.print("Enter sum of money: ");
double p = in.nextDouble();
double interest = p * 5 * 1 / 100.0;
System.out.println("Interest for the first year = " +
interest);
p += interest;
interest = p * 5 * 1 / 100.0;
System.out.println("Interest for the second year = " +
interest);
p += interest;
interest = p * 5 * 1 / 100.0;
System.out.println("Interest for the third year = " +
interest);
}
}

Output

Question 6
A businessman wishes to accumulate 3000 shares of a company.
However, he already has some shares of that company valuing ₹10
(nominal value) which yield 10% dividend per annum and receive
₹2000 as dividend at the end of the year. Write a program in Java to
calculate the number of shares he has and how many more shares to
be purchased to make his target.
Hint: No. of share = (Annual dividend * 100) / (Nominal value * div%)
public class KboatShares
{
public static void main(String args[]) {
int sharesHeld = (2000 * 100)/(10 * 10);
System.out.println("No. of shares held currently = "
+ sharesHeld);
int sharesRequired = 3000 - sharesHeld;
System.out.println("No. of shares to purchase = "
+ sharesRequired);
 }
}

Output

Question 7
Write a program to input the time in seconds. Display the time after
converting them into hours, minutes and seconds.
Sample Input: Time in seconds 5420
Sample Output: 1 Hour 30 Minutes 20 Seconds
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 + " Hours " + mins
+ " Minutes " + secs + " Seconds");
}
}

Output

Question 8
Write a program to input two unequal numbers. Display the numbers
after swapping their values in the variables without using a third
variable.
Sample Input: a = 23, b = 56
Sample Output: a = 56, b = 23
import java.util.Scanner;

public class KboatNumberSwap

{
public static void main(String args[]) {
Scanner in = new Scanner(System.in);
System.out.println("Enter two unequal numbers");
System.out.print("Enter first number: ");
int a = in.nextInt();
System.out.print("Enter second number: ");
int b = in.nextInt();
a = a + b;
b = a - b;
a = a - b;
System.out.println("a = " + a + " b = " + b);
}
}

Output

Question 9
A certain amount is invested at the rate 10% per annum for 3 years.
Find the difference between Compound Interest (CI) and Simple
Interest (SI). Write a program to take amount as an input.
Hint: SI = (P * R * T) / 100
A = P * (1 + (R/100)) T
CI = A - P
import java.util.Scanner;

public class KboatInterestDifference

{
public static void main(String args[]) {
Scanner in = new Scanner(System.in);
System.out.print("Enter Amount: ");
double p = in.nextDouble();
double si = p * 10 * 3 / 100;
double ciAmt = p * Math.pow(1 + (10/100.0), 3);
double ci = ciAmt - p;
System.out.print("Difference between CI & SI: " + (ci - si));
}
}

Output

Question 10
A shopkeeper sells two calculators for the same price. He earns 20%
profit on one and suffers a loss of 20% on the other. Write a program to
find his total cost price of the calculators by taking selling price as input.
Hint: CP = (SP / (1 + (profit / 100))) (when profit)
CP = (SP / (1 - (loss / 100))) (when loss)
import java.util.Scanner;

public class KboatShopkeeper

{
public static void main(String args[]) {
Scanner in = new Scanner(System.in);
System.out.print("Enter the selling price: ");
double sp = in.nextDouble();
double cp1 = (sp / (1 + (20 / 100.0)));
double cp2 = (sp / (1 - (20 / 100.0)));
double totalCP = cp1 + cp2;
System.out.println("Total Cost Price = " + totalCP);
}
}