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How to take multiple data types in single line on java?

I am new at coding and now I am learning Java. I tryed to write something like calculator. I wrote it with switch case but then I realized I must take all inputs in single line. For example in this code I took 3 inputs but in 3 different lines. But I must take 2 input and 1 char in single line. First first number second char and then third number. Can you help me ?
Public static void main(String[] args) {
int opr1,opr2,answer;
char opr;
Scanner sc =new Scanner(System.in);
System.out.println("Enter first number");
opr1=sc.nextInt();
System.out.println("Enter operation for");
opr=sc.next().charAt(0);
System.out.println("Enter second number");
opr2=sc.nextInt();
switch (opr){
case '+':
answer=opr1+opr2;
System.out.println("The answer is: " +answer);
break;
case '-':
answer=opr1-opr2;
System.out.println("The answer is: " +answer);
break;
case '*':
answer=opr1*opr2;
System.out.println("The answer is: " +answer);
break;
case '/':
if(opr2>0) {
answer = opr1 / opr2;
System.out.println("The answer is: " + answer);
}
else {
System.out.println("You can't divide to zero");
}
break;
default:
System.out.println("Unknown command");
break;
}

Try following way
System.out.print("Enter a number then operator then another number : ");
String input = scanner.nextLine(); // get the entire line after the prompt
String[] sum = input.split(" ");
Here numbers and operator separated by "space". Now, you can call them by sum array.
int num1 = Integer.parseInt(sum[0]);
String operator = sum[1]; //They are already string value
int num2 = Integer.parseInt(sum[2]);
Then, you can do as you did than.

You can try something like this:
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
System.out.println("Please enter number, operation and number. For example: 2+2");
String value = scanner.next();
Character operation = null;
StringBuilder a = new StringBuilder();
StringBuilder b = new StringBuilder();
for (int i = 0; i < value.length(); i++) {
Character c = value.charAt(i);
// If operation is null, the digits belongs to the first number.
if (operation == null && Character.isDigit(c)) {
a.append(c);
}
// If operation is not null, the digits belongs to the second number.
else if (operation != null && Character.isDigit(c)) {
b.append(c);
}
// It's not a digit, therefore it's the operation itself.
else {
operation = c;
}
}
Integer aNumber = Integer.valueOf(a.toString());
Integer bNumber = Integer.valueOf(b.toString());
// Switch goes here...
}
Note: didn't validate input here.

An algebra program in java is not working correctly

I made a program which should display an equation after choosing a type of algebra equation which doesn't works for some reason.
I have tried changing the scanners name but it just displays Wrong choice when an expression is chosen.
I would really appreciate it if you can help me thank you.
This is the code:
/** WAP using switch case to print the following :
1. 3X+4Y+Z
2. 3A^2+4B^3+3C*/
import java.util.*;
class F
{
public static void main(String a[])
{
Scanner in = new Scanner(System.in);
System.out.println("Algebra Program executed : No. to be typed: ");
System.out.println(" (i) 3X+4Y+Z 1 ");
System.out.println(" (ii) 3A^2+4B^3+3C 2 ");
int ch = in.nextInt();
switch(ch)
{
//Program 1
case '1': Scanner sc = new Scanner(System.in);
System.out.println("Type a number for X...");
int X = sc.nextInt();
System.out.println("Type a number for Y...");
int Y = sc.nextInt();
System.out.println("Type a number for Z...");
int Z = sc.nextInt();
int sum = (3*X)+(4*Y)+Z;
System.out.println(" ");
System.out.println("Value of X is "+X);
System.out.println("Value of Y is "+Y);
System.out.println("Value of Z is "+Z);
System.out.println("Value of 3X+4Y+Z is "+sum);
break;
//Program 2
case '2': Scanner hi = new Scanner(System.in);
System.out.println("Type a number for A...");
double A = hi.nextDouble();
System.out.println("Type a number for B...");
double B = hi.nextDouble();
System.out.println("Type a number for C...");
double C = hi.nextDouble();
double pro = 3*Math.pow(A, 2) + 4*Math.pow(B, 3) + 3*C;
int isum = (int) pro;
System.out.println(" ");
System.out.println("Value of A is "+A);
System.out.println("Value of B is "+B);
System.out.println("Value of C is "+C);
System.out.println("Value of 3A^2+4B^3+3C is "+isum);
break;
//Else
default: System.out.println("Wrong Choice");
}
}
}```

You need to change the case to case 1 and case 2 instead of case '1' and case '2'.
Note that '1' and '2' are char literals; not the int literals. the ASCII value of '1' is 49 and that of '2' is 50.

how to stop the while loop in java? [duplicate]

This question already has answers here:
How do I compare strings in Java?
(23 answers)
Closed 5 years ago.
I am new to Java and I am creating a simple calculator. I used while loop to run it continuously but I couldn't stop it, Please help me with the code.
My calculator class code is:
package calculator;
import java.util.Scanner;
public class Calculator {
public static void main(String[] args) {
Boolean keepRunning = true;
while (keepRunning) {
double a, b, out;
int n;
String ans = null;
Scanner in = new Scanner(System.in);
System.out.println("Enter two Numbers ");
a = in.nextDouble();
b = in.nextDouble();
System.out.println("Enter the mode of operation:" + "\n"
+ "1. Addition" + "\n"
+ "2. Subtraction" + "\n"
+ "3. Multiplication" + "\n"
+ "4. Division");
n = in.nextInt();
switch(n){
case 1:
out = add(a,b);
System.out.println("The output is: "+ out );
break;
case 2:
out = sub(a,b);
System.out.println("The output is: "+ out );
break;
case 3:
out = mul(a,b);
System.out.println("The output is: "+ out );
break;
case 4:
out = div(a,b);
System.out.println("The output is: "+ out );
break;
default:
System.out.println("Enter Valid option");
break;
}
System.out.println("Do you want to continue? (Y/N)");
Scanner in1 = new Scanner(System.in);
ans = in1.next();
if(ans == "Y" || ans == "y"){
}else if(ans == "N" || ans == "n"){
keepRunning = false;
System.exit(0);
}
}
}
public static double add(double a, double b){
return a+b;
}
public static double sub(double a, double b){
return a-b;
}
public static double mul(double a, double b){
return a*b;
}
public static double div(double a, double b){
return a/b;
}
}
The if loop is not at all running what's the problem in it.
Note: This question is already exist in Stackoverflow but I can't find my answer.

Don't compare strings with == in Java, use "N".equals(ans), for example. Look out to the duplicate that #EJP post for you

For loop printing twice sometimes

In my convertEuro method the for loop is causing the output to be printed twice, but only sometimes. What I mean is this is what gets displayed:
Converting values to Euros.
£4.00 >>> €5.45
£123.44 >>> €168.13
Converting values to Euros.
£4.00 >>> €5.45
£123.44 >>> €168.13
During testing it seems to do this maybe 2 times out of 10, and I can't figure out why. Code below if someone can please help:
import java.util.Scanner;
import java.text.DecimalFormat;
import java.util.ArrayList;
public class Conversion {
public void mainMenu(Scanner scan, ArrayList<Double> values, DecimalFormat twoDecimal) {
int menuChoice;
System.out.println("1. Enter values and type -1 to stop");
System.out.println("2. Euros");
System.out.println("3. Dollars");
System.out.println("4. Yen");
System.out.println("5. Rupees");
System.out.println("6. Exit");
menuChoice = scan.nextInt();
switch (menuChoice) {
case 1:
enterValues(scan, values, twoDecimal);
case 2:
scan.nextLine();
convertEuro(scan, values, twoDecimal);
}
}
public void enterValues(Scanner scan, ArrayList<Double> values, DecimalFormat twoDecimal) {
double value = 0;
do {
System.out.print("Enter value. Enter -1 to stop: £");
while (!scan.hasNextDouble()) {
System.out.print("Please enter a double (£xx.xx): £");
scan.nextLine(); //Consumes \n
scan.next();
}
value = scan.nextDouble();
if (value != -1) {
values.add(value);
System.out.println("Value entered.");
}
}
while (value != -1);
System.out.println("Returning to main menu. ");
mainMenu(scan, values, twoDecimal);
}
public void convertEuro(Scanner scan, ArrayList<Double> values, DecimalFormat twoDecimal) {
System.out.println("Converting values to Euros.");
for (int i = 0; i < values.size(); i++) {
System.out.println("£" + twoDecimal.format(values.get(i)) + " >>> " + "\u20ac" + twoDecimal.format(values.get(i) * 1.362));
}
}
public static void main(String[] args) {
Conversion conv = new Conversion();
Scanner scan = new Scanner(System.in);
ArrayList<Double> values = new ArrayList<Double>();
DecimalFormat twoDecimal = new DecimalFormat("0.00");
conv.mainMenu(scan, values, twoDecimal);
scan.close();
}
}

You need to add a break; statement:
case 1:
enterValues(scan, values, twoDecimal);
break;

When the switch statement hits the correct case, it executes it and proceeds executing other cases which are below until and unless it hit an break statement.
The correct process is
switch (menuChoice) {
case 1:
enterValues(scan, values, twoDecimal);
break;
case 2:
scan.nextLine();
convertEuro(scan, values, twoDecimal);
break;
}
Thats why best practice is to put break statement after every case end.
Thank you

Why does my calculator automatically answer "0" before i can put my sign in?

Somewhere around line 15 it gives me issues.
import java.util.Scanner;
public class Main
{
public static void main(String[] args)
{
Scanner sc = new Scanner(System.in); //scanner object created
System.out.println("Enter your first number");
int nr1 = sc.nextInt();
System.out.println("Enter your second number");
int nr2 = sc.nextInt();
System.out.println("Enter your sign (+ , - , /, *)");
String anvin = sc.nextLine();
int ans = 0;
//somewhere around this line is where it is having the problems. it gives me the answer before i can put in my sign;
if(anvin.equalsIgnoreCase("+")) {
ans = nr1 + nr2;
}
else if(anvin.equalsIgnoreCase("-")) {
ans = nr1 - nr2;
}
else if(anvin.equalsIgnoreCase("*")) {
ans = nr1 * nr2;
}
else if(anvin.equalsIgnoreCase("/")) {
ans = nr1 / nr2;
}
System.out.println(ans);
System.out.println("To continue type yes");
String yes= sc.nextLine();
if(yes.equalsIgnoreCase("yes")) {
return;
}
}
}
it answers "0" whatever I enter before I can put in my sign
Enter your first number
9
Enter your second number
9
Enter your sign (+ , - , /, *)
0
To continue type yes
please tell me what I did wrong and possibly correct it so I can understand further

Try changing your sc.nextInt() lines to Integer.parseInt(sc.nextLine()). This should make your code work correctly.
EDIT: updated the code to include a while loop to make it so you can do multiple runs per your comment. This would also require you changing your last if statement to break; instead of return;
Scanner sc = new Scanner(System. in ); //scanner object created
while (true) {
System.out.println("Enter your first number");
int nr1 = Integer.parseInt(sc.nextLine());
System.out.println("Enter your second number");
int nr2 = Integer.parseInt(sc.nextLine());
System.out.println("Enter your sign (+ , - , /, *)");
String anvin = sc.nextLine();
int ans = 0;
//somewhere around this line is where it is having the problems. it gives me the answer before i can put in my sign;
if (anvin.equalsIgnoreCase("+")) {
ans = nr1 + nr2;
} else if (anvin.equalsIgnoreCase("-")) {
ans = nr1 - nr2;
} else if (anvin.equalsIgnoreCase("*")) {
ans = nr1 * nr2;
} else if (anvin.equalsIgnoreCase("/")) {
ans = nr1 / nr2;
}
System.out.println(ans);
System.out.println("To continue type yes");
String yes = sc.nextLine();
if (!yes.equalsIgnoreCase("yes")) {
break;
}
}

Change
String anvin = sc.nextLine();
to
String anvin = sc.next();
Also keep in mind that you might divide through zero ;-)
Edit:
also change
String yes= sc.nextLine();
to
String yes= sc.next();

Instead of sc.nextLine(); use sc.next();

I would suggest you this, you can not only learn using objects but learn a better way of writing managed codes too,
Calculator.java -> a class
import java.util.Scanner;
public class Calculator {
public static void main(String[] args) {
//Instantiate
Scanner input = new Scanner(System.in);
Calculations calc = new Calculations();
// Variable declarations
double answer = 0, entry1 , entry2 ;
char operator;
// Start
System.out.println("***** Welcome to the Command line calculator program *****");
System.out.print("Please enter the first number :");
entry1 = input.nextDouble();
System.out.print("Please enter the second number:");
entry2 = input.nextDouble();
System.out.println("Please enter the operation : ");
System.out.println("***** Operations :- + -> Add ; - ->Substract ; / -> Divide ; * -> Multiply ; ^ : Power *****");
operator = input.next().charAt(0);
// Switch case
switch (operator){
case '+' : answer = calc.add(entry1, entry2);
break;
case '-' : answer = calc.substract(entry1, entry2);
break;
case '/' : answer = calc.divide(entry1, entry2);
break;
case '*' : answer = calc.multiply(entry1, entry2);
break;
case '^' : answer = calc.power(entry1, entry2);
break;
}
System.out.println(entry1 + " " + operator + " " + entry2 + " = " + answer);
}
}`
Calculations.java -->another class holding calculations
import java.math.*;
public class Calculations {
// Addition Method
double add (double first, double second){
double answer = first + second;
return answer;
}
// Substraction Method
double substract (double first, double second){
double answer = first - second;
return answer;
}
// Multiplication Method
double multiply (double first, double second){
double answer = first * second;
return answer;
}
// Division Method
double divide (double first, double second){
double answer = first / second;
return answer;
}
// Power Method
double power(double a, double b){
double answer =Math.pow(a, b);
return answer;
}
}