Develop Reference

how to make it break "when I enter -1 for the product but not enter -1 for both 2

My result want me to : when I enter -1 into (Enter the product number) it will directly break and calculate the total , but right now I have to enter -1 into (Enter the product number) and (Enter the quantity) only it will break
import java.util.Scanner;
public class Structuredcontrols {
public static void main(String[]args) {
Scanner input = new Scanner(System.in);
double sum=0;
double sum2=0;
double sum3=0;
int number = 0;
int quantity;
while (number != -1) {
System.out.print("Enter product number: ");
number = input.nextInt();
System.out.print("Enter quantity number: ");
quantity = input.nextInt();
switch (number) {
case 1:
sum += 2.98 * quantity;
break;
case 2:
sum2 += 4.50 * quantity;
break;
case 3:
sum3 += 9.98 * quantity;
break;
}
}
System.out.println("Total value of product 1 is: "+sum);
System.out.println("Total value of product 2 is: "+sum2);
System.out.println("Total value of product 3 is: "+sum3);
}
}

Just add a if statement
if(number == -1) {
break;
}
Here's full code
import java.util.Scanner;
public class structuredcontrols {
public static void main(String[] args) {
Scanner input = new Scanner(System.in);
double sum = 0;
double sum2 = 0;
double sum3 = 0;
int number = 0;
int quantity;
while (number != -1) {
System.out.print("Enter product number: ");
number = input.nextInt();
if (number == -1)
break;
System.out.print("Enter quantity number: ");
quantity = input.nextInt();
switch (number)
{
case 1:
sum += 2.98 * quantity;
break;
case 2:
sum2 += 4.50 * quantity;
break;
case 3:
sum3 += 9.98 * quantity;
break;
}
}
System.out.println("Total value of product 1 is: " + sum);
System.out.println("Total value of product 2 is: " + sum2);
System.out.println("Total value of product 3 is: " + sum3);
}
}

Total of products entered and total of all products entered using Switch

I am trying to get my output to show the total cost of each item entered and a grand total of the cost of all items, the program runs but when I try to use the end-of-file indicator nothing happens, what am I missing?
package switch1;
import java.util.Scanner;
public class Switch1 {
public static void main(String[] args) {
double total = 0;
int productCounter = 0;
int aProduct = 0;
int bProduct = 0;
int cProduct = 0;
int dProduct = 0;
int eProduct = 0;
Scanner input = new Scanner(System.in);
System.out.printf("%s%n%s%n %s%n %s%n",
"Select your product(1=bread, 2=cheese, 3=meat, 4=msutard, 5=mayo)",
"Type the end-of-file indicator to terminate input:",
"On UNIX/Linux/macOS type <Ctrl> d then press Enter",
"On Windows type <Ctrl> z then press Enter");
while (input.hasNext()) {
int product = input.nextInt();
total += product;
++productCounter;
switch (product) {
case 1:
++aProduct;
break;
case 2:
++bProduct;
break;
case 3:
++cProduct;
break;
case 4:
++dProduct;
break;
case 5:
++eProduct;
break;
}
}
System.out.printf("%nProduct Selection:%n");
if (productCounter != 0) {
double aTotal = (aProduct * 1.89);
double bTotal = (bProduct * 3.99);
double cTotal = (cProduct * 6.99);
double dTotal = (dProduct * 1.99);
double eTotal = (eProduct * 2.99);
total = (((double)aProduct * 1.89) + ((double)bProduct * 3.99) + ((double)cProduct * 6.99) + ((double)dProduct * 1.99) + ((double)eProduct * 2.99));
System.out.printf("You ordered %d gallons of milk totaling: %f%n", aProduct, aTotal);
System.out.printf("You ordered %d loaves of bread totaling: %f%n", bProduct, bTotal);
System.out.printf("You ordered %d packages of cheese totaling: %f%n", cProduct, cTotal);
System.out.printf("You ordered %d pounds of meat totaling: %f%n", dProduct, dTotal);
System.out.printf("You ordered %d bottles of mustard totaling: %f%n", eProduct, eTotal);
System.out.printf("Your total grocery bill is: %d%n", total);
}
else {
System.out.println("No products were entered");
}
}
}

Replace scanner.hasNext with scanner.hasNextLine. If you're on a newline and you hit CTRL-D (linux) or CTRL-Z (Windows), hasNextLine should return false.

Maybe a better question is "how do I find out what am I doing wrong? "
One step would be to warp you code in a try-catch block like:
try {
//the code goes here
}catch(Exception ex) {
ex.printStackTrace();
}
And see the exceptions.
It will indicate a problem in this line
System.out.printf("Your total grocery bill is: %d%n", total);

Breaking a while loop by case in Java

I need to issue break a while loop if a case is matched in a switch statement. The case is as follows: if a user enters either a number less than zero or anything greater than five. I have the switch working most of my cost except the two exceptions Ive mentioned. Here is my code:
import java.util.Scanner;
public class Product
{
public static void main(String args[])
{
int cntr = 0;
int product = 0;
int units = 0;
double totalcost = 0;
Scanner MK = new Scanner(System.in);
cntr=0;
while (cntr >= 0 && cntr <=5)
{
System.out.println("Enter Product no.(1-5) or -1 to Quit");
product = MK.nextInt();
switch(product) {
case 1:
{
System.out.println("Product " + (cntr+1));
System.out.println("Enter Quantity or -1 to Quit");
product = MK.nextInt();
double cost = 2.98;
totalcost = totalcost + cost*product;
System.out.println("Current total cost: " + totalcost);
cntr++;
}
break;
case 2:
{
System.out.println("Product " + (cntr+1));
System.out.println("Enter Quantity or -1 to Quit");
product = MK.nextInt();
double cost = 4.50;
totalcost = totalcost + cost*product;
System.out.println("Current total cost: " + totalcost);
cntr++;
}
break;
case 3:
{
System.out.println("Product " + (cntr+1));
System.out.println("Enter Quantity or -1 to Quit");
product = MK.nextInt();
double cost = 9.98;
totalcost = totalcost + cost*product;
System.out.println("Current total cost: " + totalcost);
cntr++;
}
break;
case 4:
{
System.out.println("Product " + (cntr+1));
System.out.println("Enter Quantity or -1 to Quit");
product = MK.nextInt();
double cost = 4.49;
totalcost = totalcost + cost*product;
System.out.println("Current total cost: " + totalcost);
cntr++;
}
break;
case 5:
{
System.out.println("Product " + (cntr+1));
System.out.println("Enter Quantity or -1 to Quit");
product = MK.nextInt();
double cost = 6.87;
totalcost = totalcost + (cost*product);
System.out.println("Current total cost: " + totalcost);
cntr++;
}
case 6:
{
System.out.println("Product " + (cntr+1));
System.out.println("Enter Quantity or -1 to Quit");
//product = MK.nextInt();
//double cost = 2.98;
//totalcost = totalcost + cost*product;
System.out.println("Current total cost: " + totalcost);
//cntr++;
}
break;
}
System.out.println("Total cost-->" +totalcost);
}
}
}
If anyone can point me in the right direction on how to stop my program when anything less than zero or greater than 5 is entered I would really appreciate it.

A couple of options:
Use a flag that you set when you want the loop to end (in your default or -1 clause), or
Use a labelled statement and a directed break in your default (or -1) clause
In this specific situation where you said you want the entire program to end, you could use System.exit
Here's more about option 2:
label: while (...) { // <== Labelled statement
switch (...) {
case ...:
// ...
break; // <=== Normal (undirected) break, just exits what
// it's in (switch in this case)
// ...
default:
break label; // <=== Directed break, exits loop
}
}
It's also handy for nested loops.
Side note: There's no need for the { and } you have surrounding the statements in your case clauses. The code for case continues until the break. (Yes, it's a bit different from other statements.)
Side note 2: You've said Enter Product no.(1-5) or -1 to Quit in your prompt, but you have cases for the values 1 to 6 (inclusive). You probably meant Enter Product no.(1-**6**) or -1 to Quit.

How to make the switch statement more accurate?

We were ask to make a program using the switch statement..
Here is my code:
double price = 0, totalPrice;
System.out.print("Enter the number of your choice: ");
int optionNumber = Integer.parseInt(kb.readLine());
switch(optionNumber)
{
case 1:
price = 190.00;
break;
case 2:
price = 410.00;
break;
default:
System.out.println("ERROR: Invalid number!");
break;
}
System.out.print("Enter quantity: ");
int quantity = Integer.parseInt(kb.readLine());
totalPrice = price * quantity;
So basically, the user will input a certain number and it will have different prices... inside the switch statements.
but if the user inputs a wrong number, it will display an error message and i dont want the user to enter the quantity which will be executed after the switch statement.
we are not allowed to use any methods or functions and i dont want to code repeatedly like this:
System.out.print("Enter the number of your choice: ");
int optionNumber = Integer.parseInt(kb.readLine());
switch(optionNumber)
{
case 1:
price = 190.00;
System.out.print("Enter quantity: ");
int quantity = Integer.parseInt(kb.readLine());
totalPrice = price * quantity;
System.out.print("Total price: " + totalPrice);
break;
case 2:
price = 410.00;
System.out.print("Enter quantity: ");
int quantity = Integer.parseInt(kb.readLine());
totalPrice = price * quantity;
System.out.print("Total price: " + totalPrice);
break;
default:
System.out.println("ERROR: Invalid number!");
break;
}
is there any other way not to use if else, methods, functions or coding repeatedly?
ANY HELP WILL BE APPRECIATED.

You can use a boolean flag and make it false if invalid option is selected.
Then only ask user further if flag is true.
System.out.print("Enter the number of your choice: ");
int optionNumber = Integer.parseInt(kb.readLine());
boolean flag = true;
switch (optionNumber) {
case 1:
price = 190.00;
break;
case 2:
price = 410.00;
break;
default:
flag = false;
System.out.println("ERROR: Invalid number!");
break;
}
if (flag) {
System.out.print("Enter quantity: ");
int quantity = Integer.parseInt(kb.readLine());
totalPrice = price * quantity;
System.out.print("Total price: " + totalPrice);
}

Use as this:
while(!valid option)
//do this stuff
Use a flag and set it to true if the number entered is valid, so it will go to your next instruction; else ask again for input.

Throw an exception
default:
throw new InvalidArgumentException("Invalid number!");
See also InvalidArgumentException vs UnexpectedValueException

You could just remove default from the switch statement and check to see if the price is equal to 0 after the switch statement
double price = 0, totalPrice;
System.out.print("Enter the number of your choice: ");
int optionNumber = Integer.parseInt(kb.readLine());
switch(optionNumber)
{
case 1:
price = 190.00;
break;
case 2:
price = 410.00;
break;
}
if (price == 0)
{
System.out.println("ERROR: Invalid number!");
}
else
{
System.out.print("Enter quantity: ");
int quantity = Integer.parseInt(kb.readLine());
totalPrice = price * quantity;
System.out.print("Total price: " + totalPrice);
}
This keeps you from adding unnecessary variables (like a boolean flag) when you already have one (price) with a default value of 0 that you can check against.

Java's Switch statement, adding case values together?

I have been working hard to find a solution, but no dice yet. I am stuck trying to find a way to total of the values of the cases in a switch statement together. I will provide the homework question and my progress. Which will include the class and classTest. Thanks for any suggestions.
THE Homework ?
A large company pays its salespeople on a commission basis. The salespeople receive $200 per week plus 9% of their gross sales for that week. For example, a salesperson who sells $5000 worth of merchandise in a week receives $200 plus 9% of $5000, or a total of $650. You’ve been supplied with a list of the items sold by each salesperson. The values of these items are as follows:
Item Value
1 239.99
2 129.75
3 99.95
4 350.89
Develop a Java application that inputs one salesperson’s items sold for last week and calculates and displays that salesperson’s earnings. There’s no limit to the number of items that can be sold.
*********MY ISSUE:***********************
THE ISSUE ARISES WHEN I ATTEMPT TO ENTER MORE THAN ONE ITEM. THE PROGRAM WORKS WHEN I DO ONLY A SINGLE ITEM. HOWEVER, WHEN I DO MULTIPLES, THE PROGRAM NEVER TOTALS THE VALUES TOGETHER AND THE SALESPERSON EARNINGS ARE OFF
THE CLASS*********
public class SalesCommissionCalculator
{
private String item;
private double value;
public SalesCommissionCalculator()
{
setItem("");
setValue(0.0);
}
public SalesCommissionCalculator(String i, double v)
{
setItem(i);
setValue(v);
}
public void setItem(String i)
{
item = i;
}
public void setValue(double v)
{
value = v;
}
public String getItem()
{
return item;
}
public double getValue()
{
return value;
}
public String toString()
{
return ("Item"+item+"Value"+value);
}
}
************THE ClassTest:
import javax.swing.JOptionPane;
import java.util.Scanner;
public class SalesCommissionCalculatorTest
{
public static void main(String args [])
{
int quantity;
int item;
double salary = 200.00;
double commission = 0.09;
double total= 0;
String msg="";
SalesCommissionCalculator item1 = new SalesCommissionCalculator("1", 239.99);
SalesCommissionCalculator item2 = new SalesCommissionCalculator("2", 129.75);
SalesCommissionCalculator item3 = new SalesCommissionCalculator("3", 99.95);
SalesCommissionCalculator item4 = new SalesCommissionCalculator("4", 350.89);
item=Integer.parseInt(JOptionPane.showInputDialog("Enter item number 1, 2, 3 or 4. Enter -1 to quit."));
while(item != -1)
{
switch(item)
{
case 1: quantity=Integer.parseInt(JOptionPane.showInputDialog("Enter quantity"));
total = (quantity*item1.getValue());
break;
case 2: quantity=Integer.parseInt(JOptionPane.showInputDialog("Enter quantity"));
total= (quantity*item2.getValue());
break;
case 3: quantity=Integer.parseInt(JOptionPane.showInputDialog("Enter quantity"));
total = (quantity*item3.getValue());
break;
case 4: quantity=Integer.parseInt(JOptionPane.showInputDialog("Enter quantity"));
total = (quantity*item4.getValue());
break;
default:
System.out.println("Invalid Item Number");
}
item=Integer.parseInt(JOptionPane.showInputDialog("Enter item number 1, 2, 3 or 4. Enter -1 to quit."));
}
msg = msg + String.format("Your Commission is $%.2f", (total*commission)+salary);
JOptionPane.showMessageDialog(null, msg);
}
}

You aren't accumulating the total in any of the cases. What you have right now (using case 1 as an example)
total = (quantity*item1.getValue());
just sets the total to be equal to quantity*item1.getValue(). What you probably wanted was
total += (quantity*item1.getValue());
instead. (and similarly for the other three cases)

import java.util.*;
public class Sale {
public static void main(String[] args) {
double value;
int item;
double earn= 0.0;
double total=0.0;
Scanner console = new Scanner(System.in);
System.out.print("Enter 1, 2, 3, 4 or \"-1 to quit\": ");
item = console.nextInt();
while(item != -1)
{
switch(item)
{
case 1:
System.out.print("Enter quantity: ");
int quantity= console.nextInt();
total = quantity * 239.99;
break;
case 2:
System.out.print("Enter quantity:");
quantity= console.nextInt();
total = quantity * 129.75;
break;
case 3:
System.out.print("Enter quantity: ");
quantity= console.nextInt();
total= quantity * 99.95;
break;
case 4:
System.out.print("Enter quantity: ");
quantity= console.nextInt();
total= quantity * 350.89;
break;
default: System.out.print("Invalid Item!");
}
if (total>=5000)
{
earn= total * 0.09;
System.out.print("You have earned 9%, Your salary of the week : $"+earn);
}
else
System.out.println("Your salary of the week: $"+total);
System.out.println("");
System.out.print("Enter 1, 2, 3, 4 or \"-1 to quit\": ");
item = console.nextInt();
}
System.out.println("Thank you to visit our shop!");
}
}