So far I have written choice as a string but I need to write it to accept int instead of string. The user has to enter 1, 2, 3 and if they enter 1 or 2 the program should continue but if the user enters 3 the program ends.
normally I write the choice as
String choice = "y";
while (choice.equalsIgnoreCase("y"))
{
Is there a way to write the code similar to that? I found a way using if statements but that screws up the rest of my code so I'm trying to find a way around that.
Thanks,
it would be better to to this with a so called switch construct
int choice = readInt();
switch(choice){
case 1:
case 2:
// your code
break;
case 3:
// exit code
break;
}
final int STOP_CHOICE = 3;
String choice = "1";
while (Integer.parseInt(choice) != STOP_CHOICE)
{
Note that a non-integer choice will cause Integer.parseInt to throw a NumberFormatException, so you may want to do it somewhere else and catch that possibility.
Related
I'm learning Java right now and I've never used switch statements before. I tried to enter a simple charmed quiz, but something in the switch statement isn't working.
I've tried putting text at various points in the program to test if the program every reaches that code. I have a good response inside the actual switch, so If I answer Question 1 wrong the text prompt will show up. But any later than inside the switch statement and none of my scoring output appears until all iterations of the for loop are complete. I have tried moving the "correct/incorrect" output to various points and none of them seem to work.
Scanner myScanner = new Scanner(System.in);
System.out.println("Enter your name!");
String name = myScanner.nextLine();
int wrongCounter = 0;
boolean correctChecker = false;
int score = 0;
String answer;
System.out.println("Welcome to the Charmed Quiz, " + name + "!");
for (int i = 0; i < 10; i++) {
if (wrongCounter < 4) {
switch(i) {
case 0:
System.out.println("Who read the spell that gave the Charmed Ones their powers?");
System.out.println("Enter your answer");
answer = myScanner.nextLine();
switch (answer) {
case "Pheobe":
correctChecker = true;
break;
default:
correctChecker = false;
break;
}
case 1:
System.out
.println("Who travelled to a cursed town with Prue when Pheobe was shot in a premonition?");
System.out.println("Enter your answer");
answer = myScanner.nextLine();
switch (answer) {
case "Cole":
correctChecker = true;
break;
default:
correctChecker = false;
break;
}
}
if (correctChecker == true) {
score++;
System.out.println("Correct!");
} else {
wrongCounter++;
System.out.println("Incorrect!");
}
This definitely isn't the best way of achieving a quiz game, but if you're using this as a learning exercise then the best course of action is to take the advice from #rzwitserloot.
Add a break after your main switch statement cases as opposed to the inner switch statement.
There is no real use having an inner switch statement though when you can use correctChecker = "Pheobe".equals(answer); to get a true or false boolean value in a single line.
This just means you can avoid the second switch statement which makes it way less confusing.
Altogether your cases could look something like this:
case 0:
System.out.println("Who read the spell that gave the Charmed Ones their powers?");
System.out.println("Enter your answer");
answer = myScanner.nextLine();
correctChecker = "Pheobe".equals(answer);
break;
}
In future, it would be better to store questions and answers in an array and use the for loop to iterate through that. This is a good tutorial on the subject.
Good luck with the rest of your project!
There are many, many problems with this code. The primary issue is that break breaks the closest construct it can break, which in your case is the inner switch. Whereas your intent is clearly to break out of both. Either [A] add another break right before the case 1: statement, or [B] use a labelled break; put something like outer: before the first (primary/outer) switch, and then make all those statements break outer;.
But, really, none of this (either the outer or the inner) are in any way sensible in switch form. I get that this is a learning exercise, but I'd think of something else to learn with.
Also, it's Phoebe, not Pheobe.
What I am trying to accomplish: when the user types in anything other than 1 or 2, there will be a prompt saying "I don't understand you" and it would ask the user to choose 1 or 2 again without having to run the program each time.
Something like this:
do {
String a = input.nextLine();
num = Integer.parseInt(a);
switch (num) {
case 1:
System.out.println("hello");
break;
case 2:
System.out.println("goodbye");
break;
default:
System.out.println("I don't understand you");
}
} while (num == default);
I know typing this will give me an error, so how do I compare it?
First, you have a potential infinite loop because the value for num which controls the stoping condition is never updated inside the loop.
Second, you could introduce a local variable to track when the user input was understood and exit the loop on that condition:
boolean understood;
do {
understood = false;
String a = input.nextLine();
int num = Integer.parseInt(a);
switch (num) {
case 1:
System.out.println("hello");
understood = true;
break;
case 2:
System.out.println("goodbye");
understood = true;
break;
default:
System.out.println("i dont understand u");
break;
}
} while (!understood);
What you asked is technically a while(true) since everything which is not 1 or 2 is default. Also you should probably put your scanning bit in the loop.
If you try to check if value is different from 1 and 2 to ask again for a valid option:
do
{
// stuff
}
while( num != 1 && num != 2)
Since "default" is a keyword you just can not compare it to anything. It's meaningless though, because in your condition you used all possible cases(case 1 and case 2), so your code will never end, printing either "hello" or "goodbye" forever.
If I run this code
Scanner sc = new Scanner();
while (true) {
if (sc.next().equals("1"))
System.out.println("--1--");
else if (sc.next().equals("2"))
System.out.println("--2--");
else if (sc.next().equals("3"))
System.out.println("--3--");
else if (sc.next().equals("4"))
System.out.println("--4--");
else if (sc.next().equals("help"))
System.out.println("--help--");
}
It will not read the first time I type enter. I have to type 2-4 times before it reads the input. A session could look like this:
1
1
1
1
--1--
3
3
--3--
help
2
1
help
--help--
No matter what I type, it will only read the last input of the four inputs.
Sometimes it reads after two inputs. I'm really confused about this.
Should I instead use multiple scanners?
Your concepts are wrong here.
Each time you ask for sc.next() it will wait for the input. If that input is equal to what you want it to be, then the code is executed.
You can correct this by storing sc.next() in a String variable, and then comparing it.
Here:
if (sc.next().equals("1"))
it asks for an input.
If that input is 1 then the code is executed and --1-- is printed out. Else, it jumps to this: if (sc.next().equals("2")). Now if the input is 2 then the code to print --2-- is executed. Else, it jumps to if (sc.next().equals("3")) and so on.
You can correct this by:
storing sc.next() in a String variable, and then comparing it.
using a switch-case block to compare the input.
You're calling sc.next() multiple times - so if the input isn't 1, it's going to wait for more input to see whether the next input is 2, etc. Each call to sc.next() will wait for more input. It doesn't have any idea of "that isn't the input you were looking for, so I'll return the same value next time you call".
Use a local variable to store the result of sc.next()
while (true) {
String next = sc.next();
if (next.equals("1"))
System.out.println("--1--");
else if (next.equals("2"))
System.out.println("--2--");
else if (next.equals("3"))
System.out.println("--3--");
else if (next.equals("4"))
System.out.println("--4--");
else if (next.equals("help"))
System.out.println("--help--");
}
Also consider using a switch statement instead...
You are calling sc.next() multiple times
Solution code :
Scanner scanner = new Scanner(System.in);
while(true){
switch (scanner.next()) {
case "1":
System.out.println("--1--");
break;
case "2":
System.out.println("--2--");
break;
case "3":
System.out.println("--3--");
break;
case "4":
System.out.println("--4--");
break;
case "help":
System.out.println("--help--");
break;
default:
break;
}
}
This is my first time on this site. I am taking a course in Java right now and I am having some trouble with this code/program that I am supposed to make that allows the user to select whether they want to see "good monkeys", "bad monkeys" or "show monkeys". It is nowhere near done but I am having trouble returning to the command screen/area after a command is completed. I would like the commands to be used as many times as possible. Secondly, my program treats every input if someone put in "Good Monkey". So if you put in a word like "pineapple", it will still greet you with the output designated for the "Good Monkeys" input.
I've looked online and seen that maybe I should use a "do-while" loop and use "switch". Any input/ help would be greatly appreciated. Thank you so much!
Here is my code: public class and public static and Scanner import are in this code, but for some reason I cannot add them into this post without messing up the formatting of the code.
Scanner jScanner = new Scanner(System.in);
System.out.println("please enter Good Monkeys, Bad Monkeys or Show Monkeys");
String userChoice = jScanner.nextLine();
for (int b= 1; b < 11000; b++)
{
if (userChoice.equalsIgnoreCase("Good Monkeys"));
{
System.out.println("You have selected Good Monkeys");
System.out.println("How many monkeys do you want? Put in a integer between 3 and 20");
Scanner goodMonkeyScanner = new Scanner (System.in);
int userChoiceGood = goodMonkeyScanner.nextInt();
if (userChoiceGood >= 3 && userChoiceGood <= 20)
{
System.out.println("Here you go");
System.out.println("Monkeys (metapohorical)");
break;
}
else if (userChoice.equalsIgnoreCase("Bad Monkeys"))
{
System.out.println("You have selected Bad Monkeys");
System.out.println("How many monkeys do you want? Put in a integer between 3 and 20");
Scanner badMonkeyScanner = new Scanner (System.in);
int userChoiceBad = badMonkeyScanner.nextInt();
if (userChoiceBad >= 3 && userChoiceBad <= 20)
{
System.out.println("Here you go");
System.out.println("Monkeys (metapohorical)");
break;
}
else
System.out.println("Sorry this doesn't work");
}
else if ((userChoice.equalsIgnoreCase("Show Monkeys")))
{
System.out.println("Monkeys");
System.out.println("0");
System.out.println("\\/");
System.out.println(" |");
System.out.println("/\\");
break;
}
else
{
System.out.println(" Wrong Answer. Try again");
}
break;
}
}
}
}
First, you need to define the loop. Second, you need to put the input instruction inside the loop.
I'll include a done variable to detect when the user wants to escape
So, let's code:
Scanner jScanner = new Scanner(System.in);
boolean done = false;
while(!done) {
System.out.println("please enter Good Monkeys, Bad Monkeys or Show Monkeys");
System.out.println("(or enter 'done' to exit");
String userChoice = jScanner.nextLine();
swithc(userChoice.toLowerCase()) {
case "good monkeys":
/*
* The code for this option
*/
break;
case "bad monkeys":
/*
* The code for this option
*/
break;
case "show monkeys":
/*
* The code for this option
*/
break;
case "done":
done = true;
break;
default:
System.out.println("Your input isn't what I expected!\nTry again!");
break;
}
}
The code, explained:
That while(!done) stuff can be read as "while 'not done' do what follows"
userChoice.toLowerCase(): I convert the userChoice to lower-case, to simplify comparissons. That way, I only need to compare the string with other lower-case strings
switch(userChoice.toLowerCase()): ... hmmm... I think you can figure it out yourself ;)
That default block is what happens if no other case is valid
The "done" block will set the done variable to true, and thus it will terminate the loop
Important: ALWAYS end the case blocks with break
Further reading:
The Java Tutorials: Language basics
The while and do-while statements
The switch statement
Also, I recommend you study Flowcharts and, before start coding, try to draw in paper a flowchart of your program. That way, you will have a clear image of your program before you start writing the very first line of code.
I don't think my switch statement is doing anything with my code, I'm new to java so I'm not sure how to use a switch statement in a while loop. I'm trying to take each grade/credit entered so I can find the GPA, but I added a System.out.print for the grades and it says it's worth 0 no matter what gets entered. Please help!
package exercises;
import java.text.DecimalFormat;
import javax.swing.JOptionPane;
import javax.swing.JTextArea;
public class GPA_Calculator {
public static void main(String[] args)
{
String greeting = "Hello, this program will calculate your GPA. You will be asked \n"+
"to enter your letter grade for each class, then you will be asked to enter \n"+
"the corresponding number of credits for that class. Once all the grades and credits\n"+
"have been entered, the program will display your GPA.";
JOptionPane.showMessageDialog(null,greeting,"Greeting - Introduction",1);
char gradeEntered;
String grade = "";
String creditEntered = "";
String inputGrade = "";
String inputCredit = "";
String enterGradePrompt = "Enter your letter grade (A, B, C, D, F)\n"+
"Enter Q to display your results\n\n";
String enterCreditPrompt = "Enter the credit hours for your course (0, 1, 2, 3, 4, 5, 6)\n"+
"Enter Q to display your results\n\n";
int points = 0, sum = 0, credits = 0, gradeCount = 0;
while(!inputGrade.toUpperCase().equals("Q"))
{
inputGrade = JOptionPane.showInputDialog(null,enterGradePrompt,"Enter grade",1);
gradeEntered = inputGrade.charAt(0);
grade += inputGrade.toUpperCase()+"\n";
inputCredit = JOptionPane.showInputDialog(null,enterCreditPrompt,"Enter grade",1);
creditEntered += inputCredit+"\n";
if(inputCredit.toUpperCase().equals("Q"))
continue;
credits = Integer.parseInt(inputCredit);
credits++;
switch (gradeEntered){
case 'A': points = 4;
break;
case 'B': points = 3;
break;
case 'C': points = 2;
break;
case 'D': points = 1;
break;
case 'F': points = 0;
break;
}
sum += gradeEntered;
gradeCount++;
}
// Prevents "Q" from being printed in results
grade = grade.substring(0,grade.length()-2);
creditEntered = creditEntered.substring(0,creditEntered.length()-2);
DecimalFormat df = new DecimalFormat("#.##");
double gpa = sum / gradeCount;
String results = "The courses you entered are:\n\n"+
"Grade "+"Hours \n"+
grade+" "+creditEntered+"\n"+
"Resulting in a GPA of "+df.format(gpa)+"\n\n"+
"This program will now terminate!";
JOptionPane.showMessageDialog(null, new JTextArea(results),
"results from the Invitation list generator",1);
}
}
The problem is that your switch statement is checking the value of grade, but your input is stored in inputGrade. The former is never reassigned from the empty string, so points never gets incremented.
EDIT: To expand on the comment below:
the conditional in either a while or do/while loop isn't being checked. You're checking it inside the loop and breaking out, which is fine, as you can just make an infinite loop and let the break terminate it. However, it shouldn't be duplicated in the loop conditional.
You should do check that condition early. There's no sense in performing anything inside the loop if the user enters 'q' (also, then, you don't have to have the part where you try to strip it afterwards).
Also, you should always try to keep your variables as locally as possible. There's no need to have anything but the aggregators (totalXxx and yyyEntered in this case) outside of the loop. It just makes it confusing for you in this case, as it's masking the source of your problem. When the switch statement hits the first time, it checks the empty string. The second time, it checks the first string. When you hit 'q', it breaks, and skips your last input. If these input variables were declared inside the loop, that would be immediately apparent.
Finally, while I'm here, you have an error in your gpa calculation. The points per score should take the weight of credits as a positive, not a negative. Something like:
sum(grade * credits) / sum(credits)
I can post fixed code if you want, but since I suspect this is an academic exercise, it would be more beneficial if you came to the solution yourself.
Your switch statement is using grade which seems to be never written to. It's always "".
You get inputGrade, but you don't write to grade itself.
As it is always "", you always get nothing from your switch
You are appending each grade to your gradeEntered
gradeEntered += inputGrade.toUpperCase()+"\n"; // at a point this is something like A\nB\nC\nD\nE.... so it will not match anyway
switch (gradeEntered) {
case "A": points = 4;
break;
case "B": points = 3;
break;
case "C": points = 2;
break;
case "D": points = 1;
break;
case "F": points = 0;
break;
}
so most of the times it will not match to any of your cases.
Either you have to have a separate char for grade and use it in the switch or first use switch and then append it to your variable
You are adding a newline ("\n") to your input, (inputGrade.toUpperCase()+"\n";) so none of your cases are valid.
That is, "A" does not equal "A\n"
I think you should not use "gradeEntered" and instead use:
switch (inputGrade.toUpperCase())
especially since after running the loop more than once, your "gradeEntered" string will start to look like this: "A\nB\nF\nQ\n", which is very far removed from all your cases.
Also, switching on strings is not good practice - it is a newish development in java, and won't be supported by computers running older versions fo java - though for your own use, if the compiler doesn't complain then it is fine. Still, better to get in the habit of switching on chars or ints, since most other programming languages won't let you switch on strings.