Chapter 1 - Unit 5b

Input in Java

Class 10 - APC Understanding Computer Applications with BlueJ

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Fill in the blanks

Question 1

The package needed to import StreamReader class is java.io

Question 2

nextInt() function accepts an integer by using scanner object.

Question 3

The package needed to import Scanner class is java.util

Question 4

The keyword import is used to include a package in a program.

Question 5

Division by a variable that contains a value zero is called run time error.

Question 6

input statement is used to accept value at run time.

Question 7

next() function accepts a string by using scanner object.

Question 8

void keyword refers to a non-returnable type function.

Question 9

Scanner ob = new Scanner(System.in);

Question 10

The command line argument accepts the data value as an array of Strings.

Explain the following functions

Question 1

Integer.parseInt(in.readLine());

Answer

This statement accepts an integer from the user using Stream class and parses it into int data type using Integer.parseInt() method.

Question 2

(char)(in.read());

Answer

This statement reads a character using Stream class and casts it explicitly into char data type.

Question 3

next();

Answer

next() method accepts a string from the user as a word using Scanner class.

Question 4

nextInt();

Answer

nextInt() method accepts an int value from the user using Scanner class.

Question 5

nextLine();

Answer

nextLine() method accepts a string from the user as a line of text using Scanner class.

Answer the following

Question 1

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

Answer

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 2

What is a package? Give an example.

Answer

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 3

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

Answer

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

Question 4

What is a Run Time error? Explain with an example.

Answer

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 5

What are the different types of errors that take place during the execution of a program? Name them.

Answer

Logical errors and Run-Time errors occur during the execution of the program.

Question 6

Give two differences between Syntax error and Logical error.

Answer

Syntax Error	Logical Error
Syntax Errors occur when we violate the rules of writing the statements of the programming language.	Logical Errors occur due to our mistakes in programming logic.
Program fails to compile and execute.	Program compiles and executes but doesn't give the desired output.
Syntax Errors are caught by the compiler.	Logical errors need to be found and corrected by people working on the program.

Solutions to Unsolved Java Programs

Question 1

In an election, there are candidates X and Y. On the election day, 80% of the voters go for polling, out of which 60% vote for X. Write a program to take the number of voters as input and calculate:

1. number of votes X get
2. number of votes Y get

import java.util.Scanner;

public class Polling
{
    public static void main(String args[]) {
        
        Scanner in = new Scanner(System.in);
        
        System.out.print("Enter the number of voters: ");
        long totalVoters = in.nextLong();
        
        long votedVoters = Math.round(0.8 * totalVoters);
        long xVotes = Math.round(0.6 * votedVoters);
        long yVotes = votedVoters - xVotes;
        
        System.out.println("Total Votes: " + votedVoters);
        System.out.println("Votes of X: " + xVotes);
        System.out.println("Votes of Y: " + yVotes);
    }
}

Output

Question 2

A shopkeeper offers 10% discount on the printed price of a mobile phone. However, a customer has to pay 9% 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 Invoice
{
    public static void main(String args[]) {
        
        Scanner in = new Scanner(System.in);
        
        System.out.print("Enter the MRP: ");
        double mrp = in.nextDouble();
        
        double priceAfterDiscount = mrp - (0.1 * mrp);
        double priceWithGST = priceAfterDiscount + (priceAfterDiscount * 0.09);
        
        System.out.println("Price after 10% discount and 9% GST: " + priceWithGST);
    }
}

Output

Question 3

A man spends (1/2) of his salary on food, (1/15) on rent, (1/10) on miscellaneous. Rest of the salary is his saving. Write a program to calculate and display the following:

1. money spent on food
2. money spent on rent
3. money spent on miscellaneous
4. money saved

Take the salary as an input.

import java.util.Scanner;

public class Salary
{
    public static void main(String args[]) {
        
        Scanner in = new Scanner(System.in);
        
        System.out.print("Enter the Salary: ");
        float salary = in.nextFloat();
        
        float foodSpend = salary / 2;
        float rentSpend = salary / 15;
        float miscSpend = salary / 10;
        float savings = salary - (foodSpend + rentSpend + miscSpend);
        
        System.out.println("Money spent on food: " + foodSpend);
        System.out.println("Money spent on rent: " + rentSpend);
        System.out.println("Money spent on miscellaneous: " + miscSpend);
        System.out.println("Money saved: " + savings);
    }
}

Output

Question 4

Write a program to input 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 Time
{
    public static void main(String args[]) {
        
        Scanner in = new Scanner(System.in);
        
        System.out.print("Time in seconds: ");
        int inputTime = in.nextInt();
        
        int hrs = inputTime / 3600;
        int mins = (inputTime % 3600) / 60;
        int secs = (inputTime % 3600) % 60;
        
        System.out.println(hrs 
                            + " Hours " 
                            + mins 
                            + " Minutes " 
                            + secs 
                            + " Seconds");
    }
}

Output

Question 5

The driver took a drive to a town 240 km at a speed of 60 km/h. Later in the evening, he drove back at 20 km/h less than the usual speed. Write a program to calculate:

1. the total time taken by the driver
2. the average speed during the whole journey

[Hint: average speed = total distance / total time]

public class Journey
{
    public static void main(String args[]) {
        
        int distance = 240;
        float speed = 60.0f;
        float returnSpeed = speed - 20;
        
        float time2Reach = distance / speed;
        float time2Return = distance / returnSpeed;
        float totalTime = time2Reach + time2Return;
        
        float avgSpeed = (distance * 2) / totalTime;
        
        System.out.println("Total time: " + totalTime);
        System.out.println("Average speed: " + avgSpeed);
    }
}

Output

Question 6

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 = 76, b = 65
Sample Output: a = 65, b = 76

import java.util.Scanner;

public class NumberSwap
{
    public static void main(String args[]) {
        
        Scanner in = new Scanner(System.in);
        
        System.out.println("Please provide two unequal numbers");
        
        System.out.print("Enter the first number: ");
        int firstNum = in.nextInt();
        
        System.out.print("Enter the second number: ");
        int secondNum = in.nextInt();
        
        if (firstNum == secondNum) {
            System.out.println("Invalid Input. Numbers are equal.");
            return;
        }
        
        firstNum = firstNum + secondNum;
        secondNum = firstNum - secondNum;
        firstNum = firstNum - secondNum;
        
        System.out.println("First Number: " + firstNum);
        System.out.println("Second Number: " + secondNum);
    }
}

Output

Question 7

A certain amount of money is invested for 3 years at the rate of 6%, 8% and 10% per annum compounded annually. Write a program to calculate:

1. the amount after 3 years.
2. the compound interest after 3 years.

Accept certain amount of money (Principal) as an input.
Hint: A = P * (1 + (R1 / 100))^T * (1 + (R2 / 100))^T * (1 + (R3 / 100))^T and CI = A - P

import java.util.Scanner;


public class CompoundInterest
{
    public static void main(String args[]) {
        
        Scanner in = new Scanner(System.in);
        
        System.out.print("Enter the principal: ");
        double principal = in.nextDouble();
        System.out.println(principal);
        
        float r1 = 6.0f, r2 = 8.0f, r3 = 10.0f;
        
        double amount = principal * (1 + (r1 / 100)) * (1 + (r2 / 100)) * (1 + (r3 / 100));
        double ci = amount - principal;
        
        System.out.println("Amount after 3 years: " + amount);
        System.out.println("Compound Interest: " + ci);
    }
}

Output

Question 8

The co-ordinates of two points A and B on a straight line are given as (x1,y1) and (x2,y2). Write a program to calculate the slope (m) of the line by using formula:
Slope = (y2 - y1) / (x2 - x1)
Take the co-ordinates (x1,y1) and (x2,y2) as input.

import java.util.Scanner;

public class LineSlope
{
    public static void main(String args[]) {
        
        Scanner in = new Scanner(System.in);
        
        System.out.print("Enter x coordinate of point A: ");
        int x1 = in.nextInt();
        
        System.out.print("Enter y coordinate of point A: ");
        int y1 = in.nextInt();
        
        System.out.print("Enter x coordinate of point B: ");
        int x2 = in.nextInt();
        
        System.out.print("Enter y coordinate of point B: ");
        int y2 = in.nextInt();
        
        float lineSlope = (y2 - y1) / (float)(x2 - x1);
        
        System.out.println("Slope of line: " + lineSlope);
    }
}

Output