Develop Reference

Another way except of UserInput

I would like to know how to do this with another way except of userinput? I don't want to write the values I want to do this the user
Calculate calculation = new Calculate();
int sum = calculation.sum(2, 5);
int testSum = 7;
#Test
public void testSum() {
System.out.println("#Test sum(): " + sum + " = " + testSum);
assertEquals(sum, testSum);
}
}

I guess the following might help:
public void test() {
int number1 = 0;
int number2 = 0;
int expected = 0;
System.out.println("Enter first number");
int state = 0;
Scanner scanner = new Scanner(System.in);
String input = "";
while(!input.equals("E")) {
input = scanner.nextLine();
input = input.toUpperCase();
if (!input.equals("") && Character.isDigit(input.charAt(0))){
switch(state) {
case 0:
number1 = Integer.parseInt(input);
System.out.println("Enter second number");
break;
case 1:
number2 = Integer.parseInt(input);
System.out.println("Enter expected result");
break;
case 2:
expected = Integer.parseInt(input);
System.out.println("Result: " + (number1 + number2) +
" | Expected: " + expected + System.lineSeparator());
System.out.println("Enter first number");
state = -1;
break;
default:
break;
}
state++;
}
}
scanner.close();
System.out.println("Exiting");
}

Creating a calculator that calls the methods from a separate class using scanner

I'm creating a calculator where each of the calculator's functions have to be in a separate class and called from the main method using scanner input.
1.Add
2.Subtract
3.Multiplication
4.Division
5.Square
6.Power
7.Mod operation
8.Factorial
0.Quit
I must create each method called by an object. The calculator requires one main class (has main () method) and one user defined class which has above calculating methods. The program must let the user choose an operation (one of above calculations) and operand(s) (numbers). Some calculations require two operands. (e.g. A + B, AB) Some calculations require one operand. (e.g. A2, N!) Additional functions:
•Let the calculation function continues until user wants to exit this program.
•When one calculation is done, let user choose another operation.
•This program terminates when user selects END option.
•Implement all operations. Do not use Java library math methods.
I have the code for a program that is using switch statement and case, but our class hasn't even learned any of that. I have looked everywhere online for the past two days and just can't figure it out, so apologies if the solution is simple, and thank you to all help in advance. Here is the code to my program so far.
public static void main(String[] args) {
Scanner s = new Scanner(System.in);
int choice;
do
{
System.out.println("[1] Add ");
System.out.println("[2] Subtract ");
System.out.println("[3] Multiply ");
System.out.println("[4] Division ");
System.out.println("[5] Square ");
System.out.println("[6] Power ");
System.out.println("[7] Mod Operation ");
System.out.println("[8] Factorial ");
System.out.println("[0] Quit ");
System.out.println("Please enter your choice: ");
choice = s.nextInt();
int num1, num2;
switch(choice)
{
case 1 : System.out.println("Enter two numbers to add: ");
num1 = s.nextInt();
num2 = s.nextInt();
System.out.println("The sum of " + num1 + " and " + num2 +
" is: " + add(num1, num2));
break;
case 2 : System.out.println("Enter two numbers to subtract: ");
num1 = s.nextInt();
num2 = s.nextInt();
System.out.println("The difference of " + num1 + " and " + num2 +
" is: " + diff(num1, num2));
break;
case 3 : System.out.println("Enter two numbers to multiply: ");
num1 = s.nextInt();
num2 = s.nextInt();
System.out.println("The product of " + num1 + " and " + num2 +
" is: " + prod(num1, num2));
break;
case 4 : System.out.println("Enter two numbers to divide: ");
num1 = s.nextInt();
num2 = s.nextInt();
System.out.println("The quotient of " + num1 + " and " + num2 +
" is: " + quo(num1, num2));
break;
case 5 : System.out.println("A number to square: ");
num1 = s.nextInt();
System.out.println("The square of " + num1 + " is: " + square(num1));
break;
case 6 : System.out.println("Enter the base and the exponent: ");
num1 = s.nextInt();
num2 = s.nextInt();
System.out.println("The power of " + num1 + " to the " + num2 +
"th power is: " + power(num1, num2));
break;
case 7 : System.out.println("Enter two numbers to get the interger remainder of (modulo): ");
num1 = s.nextInt();
num2 = s.nextInt();
System.out.println("The modulo of " + num1 + " and " + num2 +
" is: " + mod(num1, num2));
break;
case 8 : System.out.println("Enter a number to get the factorial of: ");
num1 = s.nextInt();
System.out.println("The factorial of " + num1 + " is: " + factorial(num1));
break;
case 0: System.out.println("Thank you for using my program...good bye!");
System.exit(0);
}
}
while(choice != 0);
s.close();
}
public static int add(int num1, int num2)
{
return num1 + num2;
}
public static int diff(int num1, int num2)
{
return num1 - num2;
}
public static int prod(int num1, int num2)
{
return num1 * num2;
}
public static double quo(int num1, int num2)
{
return (double)num1 / num2;
}
public static int mod(int num1, int num2)
{
return num1 % num2;
}
public static long power(int base, int exp)
{
long result = 1;
while (exp != 0)
{
result *= base;
--exp;
}
return result;
}
public static int square(int num)
{
return num * num;
}
public static int factorial(int base)
{
if (base == 0)
return 1;
else
return(base * factorial(base - 1));
}
}

you can use a separate class called Functions with static methods
public class Functions{
public static int add(int num1, int num2)
{
return num1 + num2;
}
public static int diff(int num1, int num2)
{
return num1 - num2;
}
public static int prod(int num1, int num2)
{
return num1 * num2;
}
public static double quo(int num1, int num2)
{
return (double)num1 / num2;
}
public static int mod(int num1, int num2)
{
return num1 % num2;
}
public static long power(int base, int exp)
{
long result = 1;
while (exp != 0)
{
result *= base;
--exp;
}
return result;
}
public static int square(int num)
{
return num * num;
}
public static int factorial(int base)
{
if (base == 0)
return 1;
else
return(base * factorial(base - 1));
}
}
and you call these methods Functions.add(num1, num2))
I'm not sure if that what you want

Here is an approach, which may be useful to you. I have done implementation for Addition and Subtraction, you can follow the same thing for other operations as well. You may want to have abstract class for single operand operations as well.
import java.util.Scanner;
public class Calculator {
public static void main(String[] args) {
Scanner s = new Scanner(System.in);
int choice;
do {
System.out.println("[1] Add ");
System.out.println("[2] Subtract ");
System.out.println("[3] Multiply ");
System.out.println("[4] Division ");
System.out.println("[5] Square ");
System.out.println("[6] Power ");
System.out.println("[7] Mod Operation ");
System.out.println("[8] Factorial ");
System.out.println("[0] Quit ");
System.out.println("Please enter your choice: ");
choice = s.nextInt();
int num1, num2;
switch (choice) {
case 1:
Addition addition = new Addition(s);
addition.performOperation();
break;
case 2:
Subtraction subtraction = new Subtraction(s);
subtraction.performOperation();
break;
case 3:
System.out.println("Enter two numbers to multiply: ");
num1 = s.nextInt();
num2 = s.nextInt();
System.out.println("The product of " + num1 + " and " + num2 +
" is: " + prod(num1, num2));
break;
case 4:
System.out.println("Enter two numbers to divide: ");
num1 = s.nextInt();
num2 = s.nextInt();
System.out.println("The quotient of " + num1 + " and " + num2 +
" is: " + quo(num1, num2));
break;
case 5:
System.out.println("A number to square: ");
num1 = s.nextInt();
System.out.println("The square of " + num1 + " is: " + square(num1));
break;
case 6:
System.out.println("Enter the base and the exponent: ");
num1 = s.nextInt();
num2 = s.nextInt();
System.out.println("The power of " + num1 + " to the " + num2 +
"th power is: " + power(num1, num2));
break;
case 7:
System.out.println("Enter two numbers to get the interger remainder of (modulo): ");
num1 = s.nextInt();
num2 = s.nextInt();
System.out.println("The modulo of " + num1 + " and " + num2 +
" is: " + mod(num1, num2));
break;
case 8:
System.out.println("Enter a number to get the factorial of: ");
num1 = s.nextInt();
System.out.println("The factorial of " + num1 + " is: " + factorial(num1));
break;
default:
System.out.println("Your choices should be 0 to 8!");
break;
}
}
while (choice != 0);
s.close();
System.out.println("Thank you for using my program...good bye!");
System.exit(0);
}
public static int prod(int num1, int num2) {
return num1 * num2;
}
public static double quo(int num1, int num2) {
return (double) num1 / num2;
}
public static int mod(int num1, int num2) {
return num1 % num2;
}
public static long power(int base, int exp) {
long result = 1;
while (exp != 0) {
result *= base;
--exp;
}
return result;
}
public static int square(int num) {
return num * num;
}
public static int factorial(int base) {
if (base == 0)
return 1;
else
return (base * factorial(base - 1));
}
}
abstract class OperationWithTwoOperands {
protected String prompt;
private Scanner scanner;
public OperationWithTwoOperands(Scanner scanner) {
this.scanner = scanner;
}
public void performOperation() {
System.out.println(prompt);
int num1 = scanner.nextInt();
int num2 = scanner.nextInt();
operation(num1, num2);
}
abstract protected void operation(int operand1, int operand2);
}
class Addition extends OperationWithTwoOperands {
public Addition(Scanner scanner) {
super(scanner);
prompt = "Enter two numbers to add:";
}
#Override
protected void operation(int num1, int num2) {
System.out.println("The sum of " + num1 + " and " + num2 + " is: " + (num1 + num2));
}
}
class Subtraction extends OperationWithTwoOperands {
public Subtraction(Scanner scanner) {
super(scanner);
prompt = "Enter two numbers to subtract:";
}
#Override
protected void operation(int num1, int num2) {
System.out.println("The difference of " + num1 + " and " + num2 + " is: " + (num1 - num2));
}
}

Saving results into csv

Here is a copy of my code,
i expected to save the results of the below code into a csv, and also ask the user do you want to review the results? if yes then display the contents of csv saved.
import java.io.*;
import java.util.Scanner;
public class TestMathOP {
public static void main(String [] args) {
float num1;
float num2;
Scanner input = new Scanner (System.in);
char choice;
do
{
System.out.print ("Enter the first number:");
num1 = input.nextFloat();
System.out.print ("Enter the second number:");
num2 = input.nextFloat();
System.out.println();
System.out.println("The sum of the numbers is " + (num1 + num2));
System.out.println("The subtract of the two numbers is " + + (num1 - num2));
System.out.print("Do you want to exit? Y/N ");
choice = input.next().charAt(0);
}
while ((choice == 'n') || (choice == 'n'));
System.out.print("Thanks for using our system");
if ((choice == 'y') || (choice == 'y'));
}
}

This should work. I think like #AlexZam said, try to go step by step.
public static void main(String[]args) throws IOException{
//creates file
File file = new File("file.csv");
//Change to strings
String num1;
String num2;
Scanner input = new Scanner (System.in);
//your choice
boolean isNo = false;
boolean isYes = false;
do
{
//enables writing to file
FileWriter fileWriter = new FileWriter("file.csv");
Scanner scanner = new Scanner(file);
System.out.print ("Enter the first number:");
float calc1;
calc1 = input.nextFloat();
String firstNumber = calc1 + "";
//WRITES TO FILE
fileWriter.write(firstNumber+"\n");
System.out.print ("Enter the second number:");
float calc2;
calc2 = input.nextFloat();
String secondNumber = calc2+"";
//WRITES TO FILE
fileWriter.write(secondNumber +"\n");
String message = "The sum of the numbers is " + (calc1 + calc2) + "\nThe subtract of the two numbers is " + (calc1 - calc2);
System.out.println(message);
fileWriter.write(message);
//close filewriting
fileWriter.close();
String question = ("Do you want to exit? Y/N ");
System.out.print(question);
String answer = input.next();
if(answer.equals("y")) {
isYes = true;
while (scanner.hasNext()) {
System.out.println(scanner.nextLine());
}
}else if(answer.equals("n")) {
isNo = true;
System.out.println("Thanks for using our systems!");
}
} while (!isNo&&!isYes);
}

Trouble with basic calculator using switch

I have already researched this question, but could not find an answer that solved my problem. I keep on getting output 0. For this assignment, I'm not allowed to use any methods. In my program, 1+2 equals 0
public static void main(String[] args) {
int result = 0;
Scanner sc = new Scanner(System.in);
System.out.println("Enter number");
int number = sc.nextInt();
System.out.println("Enter operation");
System.out.println("1.+");
System.out.println("2.-");
System.out.println("3.*");
System.out.println("4./");
System.out.println("5.=");
int operation = sc.nextInt();
while (operation != 5) {
System.out.println("Enter next number");
number = sc.nextInt();
System.out.println("Enter operation");
operation = sc.nextInt();
switch (operation) {
case 1:
result += number;
System.out.println("result= " + result);
break;
case 2:
result -= number;
System.out.println("result= " + result);
break;
case 3:
result *= number;
System.out.println("result= " + result);
break;
case 4:
result/ = number;
System.out.println("result= " + result);
break;
}
System.out.println(result);
}

import java.lang.System;
import java.util.Scanner;
public class Java{
public static void main(String args[])
{
int result = 0;
Scanner sc = new Scanner(System.in);
System.out.println("Enter number");
result = sc.nextInt();
System.out.println("Enter operation");
System.out.println("1.+");
System.out.println("2.-");
System.out.println("3.*");
System.out.println("4./");
System.out.println("5.=");
int operation = sc.nextInt();
while (operation != 5) {
System.out.println("Enter next number");
int number = sc.nextInt();
switch (operation) {
case 1:
result += number;
System.out.println("result= " + result);
break;
case 2:
result -= number;
System.out.println("result= " + result);
break;
case 3:
result *= number;
System.out.println("result= " + result);
break;
case 4:
result /= number;
System.out.println("result= " + result);
break;
}
System.out.println(result);
System.out.println("Enter operation");
operation = sc.nextInt();
}
}
}

for the first number and second number you are using the variable number..so u will get Zero.

Your first operation was not being executed.
Try this:
public static void main(String[] args) {
int result = 0;
Scanner sc = new Scanner(System.in);
System.out.println("Enter number");
result = sc.nextInt();
System.out.println("Enter operation");
System.out.println("1.+");
System.out.println("2.-");
System.out.println("3.*");
System.out.println("4./");
System.out.println("5.=");
int operation = sc.nextInt();
while (operation != 5) {
System.out.println("Enter next number");
int operand2 = sc.nextInt();
switch (operation) {
case 1:
result += operand2;
System.out.println("result= " + result);
break;
case 2:
result -= operand2;
System.out.println("result= " + result);
break;
case 3:
result *= operand2;
System.out.println("result= " + result);
break;
case 4:
result /= operand2;
System.out.println("result= " + result);
break;
}
System.out.println("Enter operation");
operation = sc.nextInt();
}
System.out.println("Global result = " + result);
}
}

The problem is that you are reading number and operation twice for the first iteration of the loop instead move the two reading condition after switch case as given below.
public static void main(String[] args) throws java.lang.Exception {
int result = 0;
Scanner sc = new Scanner(System. in );
System.out.println("Enter number");
int number = sc.nextInt();
System.out.println("Enter operation");
System.out.println("1.+");
System.out.println("2.-");
System.out.println("3.*");
System.out.println("4./");
System.out.println("5.=");
int operation = sc.nextInt();
try {
while (operation != 5) {
switch (operation) {
case 1:
result += number;
System.out.println("result= " + result);
break;
case 2:
result -= number;
System.out.println("result= " + result);
break;
case 3:
result *= number;
System.out.println("result= " + result);
break;
case 4:
result /= number;
System.out.println("result= " + result);
break;
}
System.out.println("Enter next number");
number = sc.nextInt();
System.out.println("Enter operation");
operation = sc.nextInt();
}
System.out.println("Final esult is " + result);
} catch (Exception e) {
System.out.println(e);
}
}
Output
Enter number 2
Enter operation 1
1.+
2.-
3.*
4./
5.=
result= 2
Enter next number 5
Enter operation 5
Final result is 2
Demo

Java Looping Help Needed

Recently I started programming in java so I don't know too much but I need some help. I wrote a calculator (if you can even call it that...) there isn't a gui or anything yet but I wanted to revise my code into a loop so it would take the users first number, second number and what they wanted to do (add subtract ect) and solve it and then re-loop so it would do it again. I tried a do-while loop but I couldn't get it to work.
import java.util.Scanner;
public class Calculator {
public static void main(String [] args){
Scanner in=new Scanner(System.in);
long sum = 0;
long num1 = 0;
long num2 = 0;
char s=' ';
String answer="yes";
border();
System.out.println("Acara's Calculator™ V_.01");
border();
System.out.println("What is your first number? ");
num1=in.nextInt();
System.out.println("What is your second number? ");
num2=in.nextInt();
System.out.println("What operation would you like to do?");
System.out.println("Press '+' for addition, '-' for subtraction, '/' for division or '*' for multiplication.");
s=in.next().charAt(0);
if (s=='/'){
sum=num1/num2;
System.out.println("Your answer is : " + sum);
}
else if (s=='*'){
sum=num1*num2;
System.out.println("Your answer is : " + sum);
}
else if (s=='+'){
sum=num1+num2;
System.out.println("Your answer is : " + sum);
}
else if (s=='-'){
sum=num1-num2;
System.out.println("Your answer is : " + sum);
}
border();
}
public static void border(){
System.out.println("***** ***** ***** ***** ***** ***** ***** ***** ***** *****");
}
}

Try this
import java.util.Scanner;
public class Calculator {
public static void main(String[] args) {
Scanner in = new Scanner(System.in);
long sum = 0;
long num1 = 0;
long num2 = 0;
char s = ' ';
String answer = "yes";
while (true) {
border();
System.out.println("Acara's Calculator™ V_.01");
System.out.println("What operation would you like to do?");
System.out.println("Press '+' for addition, '-' for subtraction, '/' for division or '*' for multiplication and 'q' for quit.");
s = in.next().charAt(0);
if (s == 'q') {
break;
}
border();
System.out.println("What is your first number? ");
num1 = in.nextInt();
System.out.println("What is your second number? ");
num2 = in.nextInt();
if (s == '/') {
sum = num1 / num2;
System.out.println("Your answer is : " + sum);
} else if (s == '*') {
sum = num1 * num2;
System.out.println("Your answer is : " + sum);
} else if (s == '+') {
sum = num1 + num2;
System.out.println("Your answer is : " + sum);
} else if (s == '-') {
sum = num1 - num2;
System.out.println("Your answer is : " + sum);
}
border();
}
}
public static void border() {
System.out.println("***** ***** ***** ***** ***** ***** ***** ***** ***** *****");
}
}

Here is the kind of loop you needed.
import java.util.Scanner;
public class Calculator {
public static void main(String [] args){
Scanner in=new Scanner(System.in);
long result = 0;
long num1 = 0;
long num2 = 0;
char s=' ';
String token = "";
border();
System.out.println("Acara's Calculator™ V_.01");
border();
while (true){
System.out.println("What is your first number? ... Or press ! to quit.");
token = in.next();
if ("!".equalsIgnoreCase(token.trim())){
break;
}
num1 = Integer.parseInt(token);
System.out.println("What is your second number? ... Or press ! to quit.");
token = in.next();
if ("!".equalsIgnoreCase(token.trim())){
break;
}
num2 = Integer.parseInt(token);
System.out.println("What operation would you like to do?");
System.out.println("Press '+' for addition, '-' for subtraction, '/' for division " +
"or '*' for multiplication... Or press ! if you want to quit.");
token = in.next();
if ("!".equalsIgnoreCase(token.trim())){
break;
}
s=token.trim().charAt(0);
if (s=='/'){
result=num1/num2;
System.out.println("Your answer is : " + result);
}
else if (s=='*'){
result=num1*num2;
System.out.println("Your answer is : " + result);
}
else if (s=='+'){
result=num1+num2;
System.out.println("Your answer is : " + result);
}
else if (s=='-'){
result=num1-num2;
System.out.println("Your answer is : " + result);
}
border();
}
}
public static void border() {
System.out
.println("***** ***** ***** ***** ***** ***** ***** ***** ***** *****");
}
}

This is probably what you want - it encloses your code in a while loop, but does so without making one huge main() function:
import java.util.Scanner;
public class Calculator {
private static final Scanner in = new Scanner(System.in);
public static void main(String [] args){
singleLoop();
while(shouldContinue()) {
singleLoop();
}
}
private static boolean shouldContinue() {
System.out.println("Run again? (yes/no)");
return (in.next().equalsIgnoreCase("yes"));
}
private static void singleLoop() {
long sum = 0;
long num1 = 0;
long num2 = 0;
char s=' ';
String answer="yes";
border();
System.out.println("Acara's Calculator™ V_.01");
border();
System.out.println("What is your first number? ");
num1=in.nextInt();
System.out.println("What is your second number? ");
num2=in.nextInt();
System.out.println("What operation would you like to do?");
System.out.println("Press '+' for addition, '-' for subtraction, '/' for division or '*' for multiplication.");
s=in.next().charAt(0);
if (s=='/'){
sum=num1/num2;
System.out.println("Your answer is : " + sum);
}
else if (s=='*'){
sum=num1*num2;
System.out.println("Your answer is : " + sum);
}
else if (s=='+'){
sum=num1+num2;
System.out.println("Your answer is : " + sum);
}
else if (s=='-'){
sum=num1-num2;
System.out.println("Your answer is : " + sum);
}
border();
}
public static void border(){
System.out.println("***** ***** ***** ***** ***** ***** ***** ***** ***** *****");
}
}