So everything is working fine for this calculator besides for the askCalcChoice1. Since askCalcChoice1 is a string, I am calling it wrong (obviously). The error says it cannot convert string to int, as well as convert int to boolean. However, when i make the inputOperation as a string, it breaks the other 2 calls below askCalcChoice1. (it breaks displayRedults and askTwoValues because those are not strings). I do not know how to format askCalcChoice in order to call for this method that is written in another class wihtout breaking anything. askCalcChoice is written as a string which i pasted below the oopCalculator code. Is there any way and can someone please show me how to write that portion of that code in oopCalculator?
int inputOperation; // user to choose the function
askCalcChoice1 myAskCalcChoice1 = new askCalcChoice1();
//menu becomes a complete string below
String menu = "Welcome to Hilda Wu's Calculator\t\t"
+ "\n1. Addition\n"
+ "2. Subtraction\n"
+ "3. Multiplication\n"
+ "4. Division\n"
+ "5. Exit\n\n";
calculatorCommands.pickNewSymbol(menu); //complete menu will be picked up as a string and display
calculatorCommands.putDownSymbol();
while (inputOperation = myAskCalcChoice1.calcChoice()) { //this will call for myAskCalcChoice1 class
calculatorCommands.pickNewSymbol("\n"); //pick up the class
calculatorCommands.putDownSymbol(); //display the class
askTwoValues myAskTwoValues = new askTwoValues();
float[] myFloats = myAskTwoValues.inputFloats(inputOperation);
displayResults myDisplayResults = new displayResults();
float result = myDisplayResults.showResults(inputOperation, myFloats);
String strFormat = "The answer is: " + result + "\n\n"; //print out The answer is as a string
calculatorCommands.pickNewSymbol(strFormat); //pick up string from above
calculatorCommands.putDownSymbol(); //display string
calculatorCommands.pickNewSymbol(menu); // pick up menu from the beginning of code, loop to calculator menu
calculatorCommands.putDownSymbol(); //display menu as loop
}
calculatorCommands.pickNewSymbol("\nThank you for using Hilda Wu's Calculator\n"); //when user choose to exit calculator
calculatorCommands.putDownSymbol();
}
String calcChoice() {
String input;
do { //do loop will continue to run until user enters correct response
System.out.print("Please enter a number between 1 and 5, A for Addition, S for Subtraction, M for Multiplication, or D for Division, or X for Exit: ");
try {
input = readInput.nextLine(); //user will enter a response
if (input.equals("A") || input.equals("S") || input.equals("M") || input.equals("D") || input.equals("X")) {
System.out.println("Thank you");
break; //user entered a character of A, S, M, or D
} else if (Integer.parseInt(input) >= 1 && Integer.parseInt(input) <= 5) {
System.out.println("Thank you");
break; //user entered a number between 1 and 5
} else {
System.out.println("Sorry, you have entered an invalid choice, please try again.");
}
continue;
}
catch (final NumberFormatException e) {
System.out.println("You have entered an invalid choice. Try again.");
continue; // loop will continue until correct answer is found
}
} while (true);
return input;
}
}
To start with, you are calling showResults with two arguments:
int choice
and
float [] f
Choice is never used.
You use input variable instead in your switch but on default you return the error showing choice.
Better pass choice as an argument in the function and be sure it is char and not other type.
Also this is not the form of a good stated question. I will not rate it down but please remake it so the whole code is correctly shown. I can not make sense of it easily. I might misunderstood it already. Please do not add comments between, be sure you have correct indentation and you got all the code in.
If you need to comment do it afterwards. It's not very complicated, just show us the code and ask what is wrong later ;)
If choice was meant to pass in the switch... then do it, but not as int but as char.
Related
all!
I'm a university freshman computer science major taking a programming course. While doing a homework question, I got stuck on a certain part of my code. Please be kind, as this is my first semester and we've only been doing Java for 3 weeks.
For context, my assignment is:
"Create a program that will ask the user to enter their name and to enter the number of steps they walked in a day. Then ask them if they want to continue. If the answer is "yes" ask them to enter another number of steps walked. Ask them again if they want to continue. If they type anything besides "yes" you should end the program by telling them "goodbye, [NAME]" and the sum of the number of steps that they have entered."
For the life of me, I can not get the while loop to end. It's ignoring the condition that I (probably in an incorrect way) set.
Can you please help me and tell me what I'm doing wrong?
import java.util.Scanner;
public class StepCounter
{
/**
* #param args the command line arguments
*/
public static void main(String[] args)
{
final String SENTINEL = "No";
String userName = "";
String moreNum = "";
int numStep = 0;
int totalStep = 0;
boolean done = false;
Scanner in = new Scanner(System.in);
Scanner in2 = new Scanner(System.in);
// Prompt for the user's name
System.out.print("Please enter your name: ");
userName = in.nextLine();
while(!done)
{
// Prompt for the number of steps taken
System.out.print("Please enter the number of steps you have taken: ");
// Read the value for the number of steps
numStep = in.nextInt();
// Prompt the user if they want to continue
System.out.print("Would you like to continue? Type Yes/No: ");
// Read if they want to continue
moreNum = in2.nextLine();
// Check for the Sentinel
if(moreNum != SENTINEL)
{
// add the running total of steps to the new value of steps
totalStep += numStep;
}
else
{
done = true;
// display results
System.out.println("Goodbye, " + userName + ". The total number of steps you entered is + " + totalStep + ".");
}
}
}
}
To compare the contents of String objects you should use compareTo function.
moreNum.compareTo(SENTINEL) return 0 if they are equal.
== operator is used to check whether they are referring to same object or not.
one more issue with addition of steps, addition should be done in case of "No" entered also
Use
if(!moreNum.equals(SENTINEL))
Instead of
if(moreNum != SENTINEL)
Also, make sure to add: totalStep += numStep; into your else statement so your program will actually add the steps together.
I wasn't sure how to give a title for this problem, but basically this is part of my blackjack program. Also, since I did not know how to title this, I wasn't sure how to look it up, which is why I am asking here. So I am saying that when the user enters either 1 or 11 for the ace value, if they enter something other than 1 or 11, it asks the user again to put in 1 or 11. In my program everything works fine except when the user enters 1, then it just asks the question again. The program should only asks again if the input is not equal to 1 or 11. Here is my code as I made sure it always gives an ace for testing purposes:
String card1="A";
int total=0;
Scanner input_var=new Scanner(System.in);
if (card1=="A"){
System.out.println("Do you want a 1 or 11 for the Ace?: ");
int player_ace_selection=input_var.nextInt();
if ((1|11)!=(player_ace_selection)){
System.out.println("Please enter a 1 or 11: ");
int new_selection=input_var.nextInt();
total=total + new_selection;
}
else {
total=total + player_ace_selection;
}
}
System.out.println(total);
Thanks in advance.
The expression (1|11) uses binary OR, which produces 11:
11 = 01001
1 = 00001
(11|1) = 01001
Hence, the comparison is the same as 11!=player_ace_selection
You should change the code to use logical OR, i.e.
if (1!=player_ace_selection && 11!=player_ace_selection) {
...
}
In addition, you need to fix card1 == "A" comparison for card1.equals("A")
Instead of an If statement, try a while loop. A while loop ensures that your program waits for your user to pick the right answer. You also made a mistake with your logical operations. The correct way to use "OR" in this context is to compare your user input to both '1' and '11' separately using '||'.
String card1="A";
int total=0;
Scanner input_var=new Scanner(System.in);
if (card1.equals("A")){
System.out.println("Do you want a 1 or 11 for the Ace?: ");
int player_ace_selection=input_var.nextInt();
while(player_ace_selection != 1 && player_ace_selection != 11){
System.out.println("Do you want a 1 or 11 for the Ace?: ");
player_ace_selection = input_var.nextInt();
}
total += player_ace_selection;
}
System.out.println(total);
There are some problems in your code, please consider this example and compare it with yours.
String card1="A";
int total=0;
Scanner input_var=new Scanner(System.in);
if (card1.equals("A")){ // compare the content not the reference (==)
System.out.println("Do you want a 1 or 11 for the Ace?: ");
try{ // wrap with try-catch block
int player_ace_selection = Integer.parseInt(input_var.nextLine()); //read the entire line and parse the input
if ((player_ace_selection!=1)&&(player_ace_selection!=11)){
System.out.println("Please enter a 1 or 11: ");
try{
int new_selection = Integer.parseInt(input_var.nextLine()); //again read the entire line and parse the input
total=total + new_selection;
}catch(NumberFormatException e){
// do something to catch the error
}
}
else {
total=total + player_ace_selection;
}
}catch(NumberFormatException e){
// do something to catch the error
}
System.out.println(total);
}
I'm very new to programming, especially Java. I need to create a program that counts how many orders each entry at a restaurant gets ordered. The restaurant carries 3 entries, hamburgers, salad, and special.
I need to set up my program so that the user inputs, say, "hamburger 3", it would keep track of the number and add it up at the end. If the user inputs "quit", the program would quit.
System.out.println("Enter the type (special, salad, or hamburger) of entrée followed by the number, or quit to exit the program.");
I'm thinking about using a while loop, setting it so if the user input != to "quit", then it would run.
What's difficult for me is I don't know how to make my program take into account the two different parts of the user input, "hamburger 3" and sum up the number part at the end.
At the end, I want it to say something like "You sold X hamburgers, Y salads, and Z specials today."
Help would be appreciated.
You'll probably want three int variables to use as a running tally of the number of orders been made:
public class Restaurant {
private int specials = 0;
private int salads = 0;
private int hamburger = 0;
You could then use a do-while loop to request information from the user...
String input = null;
do {
//...
} while ("quite".equalsIgnoreCase(input));
Now, you need some way to ask the user for input. You can use a java.util.Scanner easily enough for this. See the Scanning tutorial
Scanner scanner = new Scanner(System.in);
//...
do {
System.out.println("Enter the type (special, salad, or hamburger) of entrée followed by the number, or quit to exit the program.");
input = scanner.nextLine();
Now you have the input from the user, you need to make some decisions. You need to know if they entered valid input (an entree and an amount) as well as if they entered an available option...
// Break the input apart at the spaces...
String[] parts = input.split(" ");
// We only care if there are two parts...
if (parts.length == 2) {
// Process the parts...
} else if (parts.length == 0 || !"quite".equalsIgnoreCase(parts[0])) {
System.out.println("Your selection is invalid");
}
Okay, so we can now determine if the user input meets or first requirement or not ([text][space][text]), now we need to determine if the values are actually valid...
First, lets check the quantity...
if (parts.length == 2) {
// We user another Scanner, as this can determine if the String
// is an `int` value (or at least starts with one)
Scanner test = new Scanner(parts[1]);
if (test.hasInt()) {
int quantity = test.nextInt();
// continue processing...
} else {
System.out.println(parts[1] + " is not a valid quantity");
}
Now we want to check if the actually entered a valid entree...
if (test.hasInt()) {
int quantity = test.nextInt();
// We could use a case statement here, but for simplicity...
if ("special".equalsIgnoreCase(parts[0])) {
specials += quantity;
} else if ("salad".equalsIgnoreCase(parts[0])) {
salads += quantity;
} else if ("hamburger".equalsIgnoreCase(parts[0])) {
hamburger += quantity;
} else {
System.out.println(parts[0] + " is not a valid entree");
}
Take a look at The if-then and if-then-else Statements and The while and do-while Statements for more details.
You may also find Learning the Java Language of some help. Also, keep a copy of the JavaDocs at hand, it will make it eaiser to find references to the classes within the API
These two methods should be what you're looking for.
For splitting: String.split(String regex)
http://docs.oracle.com/javase/7/docs/api/java/lang/String.html#split(java.lang.String)
For parsing String into an Interger: Integer.parseInt(String s)
http://docs.oracle.com/javase/7/docs/api/java/lang/Integer.html#parseInt(java.lang.String)
You can split your strings using input.split(" "). This method gives you two strings - two parts of the main string. The character you splitted with (" ") won't be found in the string anymore.
To then get an integer out of your string, you can use the static method Integer.parseInt(inputPartWithCount).
I hope this helps!
So this is my code i dont know what to add if i want to display invalid message for the non numeric inputs please help ty
import java.util.Scanner;
public class Date
{
public static void main (String args [])
{
int x;
Scanner in = new Scanner (System.in);
System.out.print("Enter a date ");
x = in.nextInt();
while (x < 1520 || x > 3999)
{
System.out.println ("Invalid Gregorian Calendar date.");
System.out.print ("Please Input a valid Gregorian Calendar date: ");
x = in.nextInt();
}
System.out.println("Good");
Use a try catch block, and put x = in.nextInt(); inside it
I've changed your code a bit. I think this is what you were aiming for.
I'm not that good in explaining but I try to tell what I did.
First of all I got rid of your in.nextInt() since this is very restrictive. It does only accept an integer and will throw an exception if you type something else in. Normally this would be OK, but since you want the user to be able to correct the input, this will cause more troubles than it would solve.
I then put your code into an infinite loop while(true) which assures, you do not have to restart your application again once you've typed in a wrong value.
What is going on within the loop is quite simple. The console prints out what you want the user to do and reads the consoles input as a String, so you don't have to face any exceptions in the first place.
I then try to parse the given String into an integer value. I added trim() to kill leading spaces as well as trailing, so I won't have to deal with users being confused by typing in numbers with a space since they don't directly see whats wrong when getting their "not an integer" error. This would be thrown, if the input contains spaces.
Now I check whether or not the given integer-value fits your specifiation. I don't need a loop here, so I changed it to be a simple if-statement.
If the value is wrong (or lets say the if (x < 1520 || x > 3999) returns true) I'm going to print out your error message. Since we already passed casting the String input into the integer and we do not reach the else-branch we now return back to the beginning of our loop with printing out the request again before waiting for a new input to be made.
Now, as soon as the user typed in another value, e.g. 2011 (which is valid based on your specification) we will now reach the else-branch which prints the "Good" and leaves the loop by calling break. And since there is nothing left to do for the application it will stop running. If you want the user to be able to type in new values in the positive case, you simply have to remove the break-statement.
If the user types in a value which is not an integer, the cast will fail and throw a NumberFormatException. We catch this exception by surrounding the cast with the try-catch-block and print out the integer-error once we've reached the catch-block.
Then the application reacts the same way like if you typed in a wrong number and we will return to the beginning of the loop again.
The reason for putting a try-block around the Scanner is to handle closing.
import java.util.Scanner;
public class Date {
public static void main(String args[]) {
String input = "";
int x = 0;
try (Scanner in = new Scanner(System.in);) {
while (true) {
System.out.print("Please Input a valid Gregorian Calendar date: ");
input = in.nextLine();
try {
x = Integer.parseInt(input.trim());
if (x < 1520 || x > 3999) {
System.out.println("Invalid Gregorian Calendar date.");
}
else {
System.out.println("Good");
break;
}
} catch (NumberFormatException e) {
System.out.println("Given value \"" + input.trim() + "\" is not an integer.");
}
}
}
}
}
The Scanner class has a method for this
Scanner in = new Scanner(System.in);
int x;
if(in.hasNextInt()){
x = in.nextInt();
System.out.println("Valid number");
}else{
System.out.println("Not a number");
}
To keep prompting until a valid number is entered
int x;
System.out.println("Enter a number: ");
while(!in.hasNextInt()){
System.out.println("Invalid number, try again: ");
key.nextLine(); // Flush out invalid number
}
x = key.nextInt();
So I've been working on this Java program where the computer asks the user if he wants to know the square of a number. If the user's answer is either 'Y' or 'y', the computer asks the user the number he wants he wants to know the square of, and prints the square of the number. Then the computer asks the user if he wants to know the square of another number. If answer is 'Y' or 'y', the computer takes a number and prints the square. The user is again asked if he wants to know the square of another number. Like this it goes on.
I've also written code for cases where the user's answer is negative, or neither positive nor negative. By this, I meant cases where the user's answer is 'N' or 'n'. This program runs into a problem somewhere, and does not work from A to Z the way I want it to. See, when I run the code, the computer asks me if I want to know the square of a number, and I enter 'y'. I then get asked the number I want to know the square of. I enter the number and the computer prints out its square. Then I get asked if I want to know the square of another number. I enter 'y'. Then I am asked the number I want to know the square of and I enter a number. The computer prints the square of the number. Then the program asks if I want to know the square of another number and just ends, whereas it was supposed to take my answer. I've been working for almost 16 to 17 hours trying to find the bug, but I couldn't. Could you please maybe test the code and tell me where I went wrong? Thanks.
This is the code:
package looppracticea;
import java.util.Scanner;
public class LoopPracticeA {
public static void main(String[] args) {
Scanner geek = new Scanner(System.in);
Scanner geek2 = new Scanner(System.in);
long taken_number, taken_number2;
String answer, answer2, answer_not_recognized, if_answer_is_no;
answer_not_recognized = "You didn't enter any of the recognized answers.";
if_answer_is_no = "'Kay. Whatever.";
System.out.println("Do you want to know the square of a number? (Y/N)");
answer = geek.nextLine();
if (answer.equals("Y") || answer.equals("y")) {
System.out.println("The number you want to know the square of is:");
taken_number = geek.nextLong();
System.out.println("That number squared is " + taken_number * taken_number + ".");
System.out.println("Do you want to know the square of another number? (Y/N)");
answer2 = geek2.nextLine();
switch (answer2) {
case "N":
System.out.println(if_answer_is_no);
break;
case "n":
System.out.println(if_answer_is_no);
break;
case "Y":
while (answer2.equals("Y")) {
System.out.println("The number you want to know the square of is:");
taken_number2 = geek2.nextLong();
System.out.println("That number squared is " + taken_number2 * taken_number2 + ".");
System.out.println("Do you want to know the square of another number? (Y/N)");
answer2 = geek2.nextLine();
}
break;
case "y":
while (answer2.equals("y")) {
System.out.println("The number you want to know the square of is:");
taken_number2 = geek2.nextLong();
System.out.println("That number squared is " + taken_number2 * taken_number2 + ".");
System.out.println("Do you want to know the square of another number? (Y/N)");
answer2 = geek2.nextLine();
}
break;
default:
System.out.println(answer_not_recognized);
break;
}
} else if (answer.equals("N") || answer.equals("n")) {
System.out.println(if_answer_is_no);
} else {
System.out.println();
System.out.println(answer_not_recognized);
}
}
}
Here are the fixed contents of your main:
Scanner geek = new Scanner(System.in);
long taken_number;
String answer;
String answer_not_recognized = "You didn't enter any of the recognized answers.";
String if_answer_is_no = "'Kay. Whatever.";
boolean firstTime = true;
while(true)
{
if(firstTime)
System.out.println("Do you want to know the square of a number? (Y/N)");
else
System.out.println("Do you want to know the square of another number? (Y/N)");
answer = geek.nextLine();
if (answer.equalsIgnoreCase("y"))
{
System.out.println("The number you want to know the square of is:");
taken_number = geek.nextLong();
System.out.println("That number squared is " + taken_number * taken_number + ".");
answer = geek.nextLine();
}
else if (answer.equalsIgnoreCase("n")) {
System.out.println(if_answer_is_no);
break;
} else {
System.out.println();
System.out.println(answer_not_recognized);
break;
}
if(firstTime)
firstTime = false;
}
The problem is you have to read the line twice to get to the line you want.
The first nextLine will read the enter
Also I reduced the code by:
leaving only one Scanner since that is enough
used equalsIgnoreCase instead of 2 equals
used only one answer and taken_number variable since that was enough
put the variables declaration on separate lines because it is easier to maintain an a convention.
combined both input readings into one, with a boolean telling me if it is the first time so I know what message to output.
reading the nextLine() 2 times because the first one is the enter