Develop Reference

How do I loop for only specific "case" in switch/case?

I used switch/case to print yearly earnings depending on the bank account the user choose and I want to make this program, whenever the user enters inappropriate input, print "inappropriate input" message and let the user to re-enter the bank account they want to choose. But, currently my code only prints "inappropriate input" message. How can I fix it?
public static void main(String[] args) throws Exception
{
//initialize variables
String bank = "";
double money;
//asks the user to type the amount of money
Scanner myinput = new Scanner (System.in);
System.out.print("Please enter the amount of money you want in the bank: ");
//if the input is inappropriate, ensures the user to type the correct input
while (true) {
try {
money = myinput.nextDouble();
break;
} catch (Exception e) {
System.out.println("This is inappropriate. Please enter the amount of money you want in the bank: ");
myinput.nextLine();
}
}
//asks user to type the type of account they want
System.out.println("Please enter the type of account you want: ");
bank = myinput.next();
//print yearly earnings depending on the type of account that user chose
switch (bank) {
case "A" , "C": //if the user enters A or C, 1.5% of money will be yearly earnings
System.out.println("You can make $" + (Math.round((0.015 * money)*100)) / 100.0);
break;
case "B": //if the user enters A or C, 2% of money will be yearly earnings
System.out.println("You can make $" + (Math.round((0.02 * money)*100)) / 100.0);
break;
case "X": //if the user enters A or C, 5% of money will be yearly earnings
System.out.println("You can make $" + (Math.round((0.05 * money)*100)) / 100.0);
break;
default:
System.out.println ("This is inappropriate input. Please enter the type of account you want");
bank = myinput.nextLine();
}
//closing scanner
myinput.close();
}//end main

You can have one boolean variable for getting out of while-loop.
Flag is set to false in switch/case because while(false) wont iterate further.
boolean flag = true;
while(flag){
switch(bank){
case "A","C":
System.out.println("You can make $" + (Math.round((0.015 * money)*100)) / 100.0);
flag = false; //put this in all case.
break;
...
}
}

package com.javatutorial;
import java.util.Scanner;
class Main{
public static void main(String[] args) throws Exception
{
String bank = "";
double money = 0;
boolean valid = false;
Scanner myinput = new Scanner (System.in);
System.out.print("Please enter the amount of money you want in the bank: ");
while (true) {
try {
money = myinput.nextDouble();
break;
} catch (Exception e) {
System.out.println("This is inappropriate. Please enter the amount of money you want in the bank: ");
myinput.next();
}
}
do {
System.out.println("Please enter the type of account you want: ");
bank = myinput.next();
switch (bank) {
case "A":
case "C":
System.out.println("You can make $" + (Math.round((0.015 * money) * 100)) / 100.0);
valid = true;
break;
case "B":
System.out.println("You can make $" + (Math.round((0.02 * money) * 100)) / 100.0);
valid = true;
break;
case "X":
System.out.println("You can make $" + (Math.round((0.05 * money) * 100)) / 100.0);
valid = true;
break;
default:
System.out.println("This is inappropriate input. Please enter the type of account you want");
}
}while( !valid);
}
}

Java, ending a applet based on choice

I'm just starting out in java and I'm trying to make my applet only stop when I type "n" or "N". If I type "y or "Y" I want it to run the other code.
Here is the code:
public static void main(String[] args) {
// welcome the user to the program
System.out.println("Welcome to the Invoice Total Calculator");
System.out.println(); // print a blank line
// create a Scanner object named sc
Scanner sc = new Scanner(System.in);
// perform invoice calculations until choice isn't equal to "y" or "Y"
String choice = "y";
while (choice.equalsIgnoreCase("y"))
{
// get the invoice subtotal from the user
System.out.print("Enter subtotal: ");
double subtotal = sc.nextDouble();
// calculate the discount amount and total
double discountPercent= 0.0;
if (subtotal >= 200)
discountPercent = .2;
else if (subtotal >= 100)
discountPercent = .1;
else
discountPercent = 0.0;
double discountAmount = subtotal * discountPercent;
double total = subtotal - discountAmount;
// display the discount amount and total
String message = "Discount percent: " + discountPercent + "\n"
+ "Discount amount: " + discountAmount + "\n"
+ "Invoice total: " + total + "\n";
System.out.println(message);
// see if the user wants to continue
System.out.print("Continue? (y/n): ");
choice = sc.next();
System.out.println();
}
}
}

if you're trying to implement an applet then you should subclass from Applet... but if you implement an Application (looks like you're doing it so right now) then you can quit your application by simply calling System.exit(0);
your programm will quit also when you simply leave your while(...)-loop, you can do it by calling
// see if the user wants to continue
System.out.print("Continue? (y/n): ");
choice = sc.next();
System.out.println();
if("n".equalsIgnoreCase(choice){
break;//this will make you jump out of the while loop
}

My Code won't stop printing in a loop

import java.util.InputMismatchException;
import java.util.Scanner;
public class Bank
{
double balance = 0;
double amount = 0;
Scanner in = new Scanner(System.in);
int userChoice;
BankAccount account1 = new BankAccount();
boolean quit = false;
{
do {
System.out.println("Your Choice: ");
System.out.println("For Deposit type 1");
System.out.println("For Withdraw type 2");
System.out.println("For Check Balance type 3");
System.out.println("Type 0 to quit");
userChoice = in.nextInt();
switch (userChoice) {
case 1:
//Deposit Money
boolean inputInvalid = false;
do {
System.out.println("How Much would you like to deposit?");
try {
in.useDelimiter("\n");
amount = in.nextDouble();
inputInvalid = false;
} catch(InputMismatchException ime) {
System.out.println("Invalid input. Try Again");
inputInvalid = true;
}
} while (inputInvalid);
System.out.println("Depositing: " + amount);
account1.deposit(amount);
//balance = amount + balance;
break;
case 2:
//Withdraw money
boolean InvalidInput = false;
do {
System.out.println("How Much would you like to withdraw?");
try {
in.useDelimiter("\n");
amount = in.nextDouble();
InvalidInput = false;
} catch(InputMismatchException ime) {
System.out.println("Invalid input. Try Again");
InvalidInput = true;
}
} while (InvalidInput);
System.out.println("Withdrawing: " + amount);
account1.withdraw(amount);
//balance = balance - amount;
break;
case 3:
//check balance
System.out.println("Checking Balance.");
account1.getBalance();
System.out.println(account1.balance);
break;
case 0:
System.out.println("Thanks for Using BankAccount Banking System!");
quit = true;
break;
default:
System.out.println("Error: Choice not recognized please choose again.");
continue;
}
if (userChoice == 0)
quit = true;
} while
(!quit);
}
}
My code otherwise works fine but I can't seem to figure out why it won't stop repeatedly printing my error message for the user. If someone can point out my error for me that would be fantastic. I did have this same code in another question however they fixed my problem that I had in the last question and were unable to answer the problem that arose here.

You need to remove or comment out the following line from your code :
in.useDelimiter("\n");
This is causing the the character "\n" to be passed to the amount = in.nextDouble(), which in turn causes the InputMismatchException to be thrown , thus resulting in an infinite loop.
UPDATE : Working code and the Sample output for your convinience:
import java.util.InputMismatchException;
import java.util.Scanner;
public class Bank {
public static void main(String[] args) {
double balance = 0;
double amount = 0;
#SuppressWarnings("resource")
Scanner in = new Scanner(System.in);
int userChoice;
BankAccount account1 = new BankAccount();
boolean quit = false;
{
do {
System.out.println("Your Choice: ");
System.out.println("For Deposit type 1");
System.out.println("For Withdraw type 2");
System.out.println("For Check Balance type 3");
System.out.println("Type 0 to quit");
System.out.print("User Input :");
userChoice = in.nextInt();
switch (userChoice) {
case 1:
// Deposit Money
boolean inputInvalid = false;
do {
System.out.println("How Much would you like to deposit?");
try {
// in.useDelimiter("\n");
amount = in.nextDouble();
inputInvalid = false;
} catch (InputMismatchException ime) {
System.out.println("Invalid input. Try Again");
inputInvalid = true;
}
} while (inputInvalid);
System.out.println("Depositing: " + amount);
account1.deposit(amount);
// balance = amount + balance;
break;
case 2:
// Withdraw money
boolean InvalidInput = false;
do {
System.out.println("How Much would you like to withdraw?");
try {
// in.useDelimiter("\n");
amount = in.nextDouble();
InvalidInput = false;
} catch (InputMismatchException ime) {
System.out.println("Invalid input. Try Again");
InvalidInput = true;
}
} while (InvalidInput);
System.out.println("Withdrawing: " + amount);
account1.withdraw(amount);
// balance = balance - amount;
break;
case 3:
// check balance
System.out.println("Checking Balance.");
account1.getBalance();
System.out.println("Available Balance is : " + account1.getBalance());
break;
case 0:
System.out.println("Thanks for Using BankAccount Banking System!");
quit = true;
break;
default:
System.out.println("Error: Choice not recognized please choose again.");
continue;
}
if (userChoice == 0)
quit = true;
} while (!quit);
}
}
}
Sample Output :
Your Choice:
For Deposit type 1
For Withdraw type 2
For Check Balance type 3
Type 0 to quit
User Input :1
How Much would you like to deposit?
100
Depositing: 100.0
Your Choice:
For Deposit type 1
For Withdraw type 2
For Check Balance type 3
Type 0 to quit
User Input :25
Error: Choice not recognized please choose again.
Your Choice:
For Deposit type 1
For Withdraw type 2
For Check Balance type 3
Type 0 to quit
User Input :2
How Much would you like to withdraw?
25
Withdrawing: 25.0
Your Choice:
For Deposit type 1
For Withdraw type 2
For Check Balance type 3
Type 0 to quit
User Input :3
Checking Balance.
Available Balance is : 75.0
Your Choice:
For Deposit type 1
For Withdraw type 2
For Check Balance type 3
Type 0 to quit
User Input :0
Thanks for Using BankAccount Banking System!

Try this
String value = in.nextLine();
String v="";
for(int i=0;i<value.length();i++)
if(value.charAt(i)!='\n')
v+=value.charAt(i);
double amount =-1;
if(v!=null)
amount = Double.parseDouble(v);

Arrays and bank accounts in Java

I am trying to write a simple Bank Account Management program that does the following:
Creates a new account with Account number and Balance taken from user and stored in an array
Selects an account (from the array)
Deletes the account selected
Withdraw and Deposit into account selected.
Problem: I don't understand what the my mistakes are.
I tried using different types of arrays for account number and balance storing, but I didn't not find the answer yet. I search the web and Stackoverflow for references, documentations, simple examples, but could not find any (the ones that I found, use some commands and things that I haven't learned yet so I can understand how they work). I am a beginner, I am still learning and would appreciate some advice. Thanks!
//Bank account class
public class account {
private int ANumber;
private double balance;
public account(double initialBalance, int accno) {
balance = initialBalance;
ANumber = accno;
}
public void deposit (double u_amm){
balance += u_amm;
}
public double withdraw(double amount) {
balance -= amount;
return amount;
}
public double getBalance() {
return balance;
}
public int getAccount(){
return ANumber;
}
}
And this is the Main class
import java.util.Scanner;
// main class
public class bankmain {
public static void main(String[] args) {
Scanner scan = new Scanner(System.in);
// Menu starts from here
Scanner input = new Scanner(System.in);
System.out.println("Enter the option for the operation you need:");
System.out.println("****************************************************");
System.out.println("[ Options: ne - New Account de - Delete Account ]");
System.out.println("[ dp - Deposit wi - Withdraw ]");
System.out.println("[ se - Select Account ex - Quit ]");
System.out.println("****************************************************");
System.out.print("> "); //indicator for user input
String choice = input.next();
//Options
while(true){
if(choice == "ne"){
int nacc;
int bal;
int [][]array = new int[nacc][bal]; // Array for account and balance
System.out.print("Insert account number: ");
nacc =input.nextInt(); //-- Input nr for array insertion
System.out.print("Enter initial balance: ");
bal=input.nextInt(); //-- Input nr for array insertion
System.out.println("Current account: " + nacc + " " + "Balance " + bal);
break;
}
// account selection
if(choice.equals("se")){
System.out.println("Enter number of account to be selected: ");
//user input for account nr from array
System.out.println("Account closed.");
}
//close account
if(choice.equals("de")){
//array selected for closing
System.out.println("Account closed.");
}
// deposit
if(choice.equals("dp")){
System.out.print("Enter amount to deposit: ");
double amount = scan.nextDouble();
if(amount <= 0){
System.out.println("You must deposit an amount greater than 0.");
} else {
System.out.println("You have deposited " + (amount + account.getBalance()));
}
}
// withdrawal
if(choice.equals("wi")){
System.out.print("Enter amount to be withdrawn: ");
double amount = scan.nextDouble();
if (amount > account.balance()){
System.out.println("You can't withdraw that amount!");
} else if (amount <= account.balance()) {
account.withdraw(amount);
System.out.println("NewBalance = " + account.getBalance());
}
}
//quit
if(choice == "ex"){
System.exit(0);
}
} // end of menu loop
}// end of main
} // end of class

Your code was wrong on many levels - first try to work on your formatting and naming conventions so you don't learn bad habbits. Dont use small leters for naming classes, try to use full words to describe variables and fields, like in that Account.class example:
public class Account {
private Integer accountNumber;
private Double balance;
public Account(final Integer accountNumber, final Double initialBalance) {
this.accountNumber = accountNumber;
balance = initialBalance;
}
public Double deposit (double depositAmmount) {
balance += depositAmmount;
return balance;
}
public Double withdraw(double withdrawAmmount) {
balance -= withdrawAmmount;
return balance;
}
public Double getBalance() {
return balance;
}
public Integer getAccountNumber() {
return accountNumber;
}
}
Also try to use the same formatting(ie. spaces after brackets) in all code, so that it's simpler for you to read.
Now - what was wrong in your app:
Define the proper holder for your accounts i.e. HashMap that will hold the information about all accounts and will be able to find them by accountNumber.
HashMap<Integer, Account> accountMap = new HashMap<Integer, Account>();
This one should be inside your while loop, as you want your user to do multiple tasks. You could ommit the println's but then the user would have to go back to the top of the screen to see the options.
System.out.println("Enter the option for the operation you need:");
System.out.println("****************************************************");
System.out.println("[ Options: ne - New Account de - Delete Account ]");
System.out.println("[ dp - Deposit wi - Withdraw ]");
System.out.println("[ se - Select Account ex - Quit ]");
System.out.println("****************************************************");
System.out.print("> "); //indicator for user input
String choice = input.nextLine();
System.out.println("Your choice: " + choice);
You shouldn't compare Strings using '==' operator as it may not return expected value. Take a look at: How do I compare strings in Java? or What is the difference between == vs equals() in Java?. For safty use Objects equals instead, ie:
choice.equals("ne")
There was no place where you created the account:
Account newAccount = new Account(newAccountNumber, initialBalance);
You didn't use if-else, just if's. It should look more like that (why to check if the choice is 'wi' if it was already found to be 'ne'):
if(choice.equals("ne")) {
//doStuff
} else if choice.equals("se") {
//doStuff
} //and so on.
If your using Java version >= 7 then instead of if-else you can use switch to compare Strings.
There was no notification of the wrong option:
} else {
System.out.println("Wrong option chosen.");
}
You didn't close your Scanner object. This really doesn't matter here, as it's in main method and will close with it, but it's a matter of good habbits to always close your streams, data sources etc when done using it:
input.close();
So the whole code can look like this:
import java.util.HashMap;
import java.util.Scanner;
// main class
public class BankAccount {
public static void main(String[] args) {
Scanner input = new Scanner(System.in);
HashMap<Integer, Account> accountMap = new HashMap<Integer, Account>();
//Options
while(true) {
System.out.println("Enter the option for the operation you need:");
System.out.println("****************************************************");
System.out.println("[ Options: ne - New Account de - Delete Account ]");
System.out.println("[ dp - Deposit wi - Withdraw ]");
System.out.println("[ se - Select Account ex - Quit ]");
System.out.println("****************************************************");
System.out.print("> "); //indicator for user input
String choice = input.next();
System.out.println("Your choice: " + choice);
if(choice.equals("ne")) {
Integer newAccountNumber;
Double initialBalance;
Account newAccount;
// Array for account and balance
System.out.print("Insert account number: ");
newAccountNumber = input.nextInt(); //-- Input nr for array insertion
System.out.print("Enter initial balance: ");
initialBalance=input.nextDouble(); //-- Input nr for array insertion
newAccount = new Account(newAccountNumber, initialBalance);
accountMap.put(newAccountNumber, newAccount);
System.out.println("New Account " + newAccountNumber + " created with balance: " + initialBalance);
}
//select account
else if(choice.equals("se")) {
System.out.println("Enter number of account to be selected: ");
Integer accountToGetNumber = input.nextInt();
Account returnedAccount = accountMap.get(accountToGetNumber);
if (returnedAccount != null)
{
System.out.println("Account open. Current balance: " + returnedAccount.getBalance());
}
else
{
//user input for account nr from array
System.out.println("Account does not exist.");
}
}
//close account
else if(choice.equals("de"))
{
System.out.println("Enter number of account to be selected: ");
Integer accountToDeleteNumber = input.nextInt();
Account removedAccount = accountMap.remove(accountToDeleteNumber);
if (removedAccount != null)
{
System.out.println("Account " + removedAccount.getAccountNumber() + " has been closed with balance: " + removedAccount.getBalance());
}
else
{
//user input for account nr from array
System.out.println("Account does not exist.");
}
}
// deposit
else if(choice.equals("dp")) {
System.out.println("Enter number of account to deposit: ");
Integer accountToDeposit = input.nextInt();
System.out.print("Enter amount to deposit: ");
double amount = input.nextDouble();
if(amount <= 0){
System.out.println("You must deposit an amount greater than 0.");
} else {
accountMap.get(accountToDeposit).deposit(amount);
System.out.println("You have deposited " + (amount));
System.out.println("Current balance " + accountMap.get(accountToDeposit).getBalance());
}
}
// withdrawal
else if(choice.equals("wi")) {
System.out.println("Enter number of account to withdraw: ");
Integer accountToWithdraw = input.nextInt();
System.out.print("Enter amount to withdraw: ");
double amount = input.nextDouble();
if(amount <= 0) {
System.out.println("You must deposit an amount greater than 0.");
} else {
accountMap.get(accountToWithdraw).withdraw(amount);
System.out.println("You have deposited " + (amount));
System.out.println("Current balance " + accountMap.get(accountToWithdraw).getBalance());
}
}
//quit
else if(choice.equals("ex")) {
break;
} else {
System.out.println("Wrong option.");
} //end of if
} //end of loop
input.close();
} //end of main
} //end of class
There still is much to improve, i.e. input validation - but this should work for the begining.

You have written the above code, but it has many mistakes. You need to learn the The basics of Java programming.
I have modified your program to perform below operations :-
Create new account.
Select existing account.
Deposit amount.
Withdraw amount.
View balance.
Delete account.
Exit.
Account.java :
/**
* This class performs bank operations
*/
public class Account {
private int accNumber;
private double balance;
public Account(double initialBalance, int accNo) {
balance = initialBalance;
accNumber = accNo;
}
public void deposit(double amount) {
balance += amount;
}
public double withdraw(double amount) {
balance -= amount;
return amount;
}
public double getBalance() {
return balance;
}
public int getAccNumber() {
return accNumber;
}
}
BankMain.java :
public class BankMain {
private static double amount;
private static ArrayList<Account> accountList = new ArrayList<>();
private static Account selectedAccount;
private static boolean flag = false;
public static void main(String[] args) {
Scanner scan = new Scanner(System.in);
// Menu starts from here
Scanner input = new Scanner(System.in);
System.out.println("Enter the option for the operation you need:");
System.out
.println("****************************************************");
System.out
.println("[ Options: new - New Account del - Delete Account ]");
System.out
.println("[ dp - Deposit wi - Withdraw bal - Check balance ]");
System.out
.println("[ se - Select Account exit - Quit ]");
System.out
.println("****************************************************");
Account account = null;
while (true) {
System.out.println("> "); // indicator for user input
String choice = input.next();
// Options
switch (choice) {
case "new":
// Create new account
int accNo = 0;
int bal = 0;
System.out.println("Enter account number : ");
accNo = input.nextInt();
System.out.println("Enter initial balance: ");
bal = input.nextInt();
System.out.println("Current account: " + accNo + " "
+ "Balance " + bal);
account = new Account(bal, accNo);
accountList.add(account);
break;
case "se":
// select account
System.out
.println("Enter account number for further operations : ");
int selectedAcc = scan.nextInt();
System.out.println("Selected account : " + selectedAcc);
for (Object object : accountList) {
selectedAccount = (Account) object;
if (selectedAccount.getAccNumber() == selectedAcc) {
flag = true;
break;
} else {
flag = false;
}
}
if (!flag) {
System.out.println("Account doesn't exists.");
}
if (accountList.size() == 0) {
System.out.println("Zero account exists.");
}
break;
case "del":
// close account
System.out
.println("Enter account number for further operations : ");
int selectedAcc1 = scan.nextInt();
System.out.println("Selected account : " + selectedAcc1);
Iterator<Account> iterator = accountList.iterator();
while (iterator.hasNext()) {
selectedAccount = (Account) iterator.next();
if (selectedAccount.getAccNumber() == selectedAcc1) {
iterator.remove();
flag = true;
break;
}
}
if (!flag) {
System.out.println("Account doesn't exists.");
}
System.out.println("Account " + selectedAcc1 + " closed.");
break;
case "dp":
// Deposit amount
System.out.println("Enter amount to deposit : ");
amount = scan.nextDouble();
if (amount <= 0) {
System.out
.println("You must deposit an amount greater than 0.");
} else {
if (flag) {
selectedAccount.deposit(amount);
System.out.println("You have deposited " + amount
+ ". Total balance : "
+ (selectedAccount.getBalance()));
} else {
System.out.println("Please select account number.");
}
}
break;
case "wi":
// Withdraw amount
System.out.println("Enter amount to be withdrawn: ");
amount = scan.nextDouble();
if (amount > account.getBalance() && amount <= 0) {
System.out.println("You can't withdraw that amount!");
} else if (amount <= selectedAccount.getBalance()) {
if (flag) {
selectedAccount.withdraw(amount);
System.out.println("You have withdraw : " + amount
+ " NewBalance : "
+ selectedAccount.getBalance());
} else {
System.out.println("Please select account number.");
}
}
break;
case "bal":
// check balance in selected account
if (flag) {
System.out.println("Your current account balance : "
+ selectedAccount.getBalance());
} else {
System.out.println("Please select account number.");
}
break;
case "exit":
default:
// quit
System.out.println("Thank You. Visit Again!");
flag = false;
input.close();
scan.close();
System.exit(0);
break;
}
} // end of menu loop
}// end of main
} // end of class
I have tested this code & it is working fine.
Output :
Enter the option for the operation you need:
****************************************************
[ Options: new - New Account del - Delete Account ]
[ dp - Deposit wi - Withdraw bal - Check balance ]
[ se - Select Account exit - Quit ]
****************************************************
> new
Enter account number : 101
Enter initial balance: 10000
Current account: 101 Balance 10000
> new
Enter account number : 102
Enter initial balance: 25000
Current account: 102 Balance 25000
> se
Enter account number for further operations : 103
Selected account : 103
Account doesn't exists.
> se
Enter account number for further operations : 101
Selected account : 101
> bal
Your current account balance : 10000.0
> dp
Enter amount to deposit : 2500
You have deposited 2500.0. Total balance : 12500.0
> wi
Enter amount to be withdrawn: 500
You have withdraw : 500.0 NewBalance : 12000.0
> se
Enter account number for further operations : 102
Selected account : 102
> bal
Your current account balance : 25000.0
> del
Enter account number for further operations : 101
Selected account : 101
Account 101 closed.
> se
Enter account number for further operations : 101
Selected account : 101
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Return Switch case to main program in Java [closed]

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I know this is an easy question, but I am new to Java and am so lost. All that is left to do in my program is output a message saying something like "Invalid input, try again" at the end of each case in my program if the user does not enter either a yes or a no and return to the point where it asks for another calculation. I know it's elementary and I looked for an answer the best I could but I simply don't know enough of the java terminology. If you could help me I would appreciate it so much!
P.S.It was pointed out to me that my variables should not begin with capital letters, I am aware and will not do it in the future.
System.out.println(" The purpose of this program is to calculate the speed of sound through several mediums.\n The program user will input a distance in feet followed by a mediumd and the program will output the speed in feet per second and miles per hour\n");
//declare variables
Scanner keyboard = new Scanner(System.in);
final double Air = 1126.1;
final double Water = 4603.2;
final double Steel = 20013.3;
final double Earth = 22967.4;
double OneFootPerSecond = .68181818182;
double Distance;
double AirSpeed;
double WaterSpeed;
double SteelSpeed;
double EarthSpeed;
boolean shouldContinue = true;
while (shouldContinue == true){
System.out.print(" What is the distance in feet:" );
//ask the user to input variables
while (!keyboard.hasNextDouble()){
System.out.println("Please enter a valid numeric value, try again: ");
keyboard.next();
}
Distance =keyboard.nextDouble();
{
System.out.print("Input the media: Air, Water, Steel, or Earth: ");
String Input = keyboard.next();
switch(Input.toLowerCase())
{
case "air":
AirSpeed = Distance/Air;
System.out.print("\n \nThe time to for sound to travel ");
System.out.print(Distance);
System.out.print(" feet through AIR" +"\n");
System.out.printf("%.6f", AirSpeed);
System.out.print(" seconds or ");
System.out.printf("%.1f", OneFootPerSecond*Air);
System.out.print(" miles per hour.");
System.out.print("\n \nEnter Yes for another calculation, else No: ");
String Another = keyboard.next();
Another.toLowerCase();
if (Another.equals("no")){
shouldContinue = false;
}
if (!Another.equals("no"))
if (!Another.equals("yes"))
{System.out.print("Invalid.");
}
break;
case "water":
WaterSpeed = Distance/Water;
System.out.print("\nThe time to for sound to travel ");
System.out.print(Distance);
System.out.print(" feet through WATER" +"\n");
System.out.printf("%.6f",WaterSpeed);
System.out.print(" seconds or ");
System.out.printf("%.1f", OneFootPerSecond*Water);
System.out.print(" miles per hour.");
System.out.print("\n \nEnter Yes for another calculation, else No: ");
Another = keyboard.next();
Another.toLowerCase();
if (Another.equals("yes")){
shouldContinue = false;
}
break;
case "steel":
SteelSpeed = Distance/Steel;
System.out.print("\nThe time to for sound to travel ");
System.out.print(Distance);
System.out.print(" feet through STEEL" +"\n");
System.out.printf("%.6f",SteelSpeed);
System.out.print(" seconds or ");
System.out.printf("%.1f", OneFootPerSecond*Steel);
System.out.print(" miles per hour.");
System.out.print("\n \nEnter Yes for another calculation, else No: ");
Another = keyboard.next();
Another.toLowerCase();
if (Another.equals("yes")){
shouldContinue = false;
}
break;
case "earth":
EarthSpeed = Distance/Water;
System.out.print("\nThe time to for sound to travel ");
System.out.print(Distance);
System.out.print(" feet through EARTH" +"\n");
System.out.printf("%.6f",EarthSpeed);
System.out.print(" seconds or ");
System.out.printf("%.1f", OneFootPerSecond*Earth);
System.out.print(" miles per hour.");
System.out.print("\n \nEnter Yes for another calculation, else No: ");
Another = keyboard.next();
Another.toLowerCase();
if (Another.equals("yes")){
shouldContinue = false;
}
break;
default :
System.out.print("Invalid. Re-run the program. ");
break;
}
}

Considering you want to ask for another calculation for every case, to prevent duplicated code move the prompt for additional processing out of the cases and put it after the switch statement. Then provide a method to continue prompting the user until they enter acceptable input.
public boolean promptForContinue(final Scanner keyboard) {
boolean isValid = false;
String userInput = "";
do {
userInput = keyboard.next();
isValid = userInput.matches("Yes|No");
if (!isValid) {
System.out.println("Invalid entry.");
}
} while (!isValid);
return userInput.equals("Yes") ? true : false;
}
EDIT: Alternative implementation removing the need for extra local variables and removing the usage of regex. Also, the addition of .toLowerCase() expands the acceptable input without the need of additional case statements. For this simple use case, we can take advantage of the fall through effect of case statements to expand acceptable values to 8.
private static boolean promptForContinue(final Scanner keyboard)
{
do
{
System.out.print("Continue (Yes/No) ?");
final String userInput = keyboard.next().toLowerCase();
switch(userInput)
{
case "y":
case "yes": return true;
case "n":
case "no": return false;
default :
System.out.println("Invalid Entry.");
}
}
while (true);
}
Then shouldContinue would be set to the return value of that method in the end of your while loop.
shouldContinue = promptForContinue(keyboard);
Incorporating what you had with my suggestion the file should look something like the following. Also, I would suggest storing both calculations in a variable so that you could move the duplicated print statements out of the cases.
public static void main(String[] args)
{
System.out.println(" The purpose of this program is to calculate the speed of sound through several mediums.\n The program user will input a distance in feet followed by a mediumd and the program will output the speed in feet per second and miles per hour\n");
//declare variables
Scanner keyboard = new Scanner(System.in);
final double Air = 1126.1;
final double Water = 4603.2;
final double Steel = 20013.3;
final double Earth = 22967.4;
double OneFootPerSecond = .68181818182;
double Distance;
double AirSpeed;
double WaterSpeed;
double SteelSpeed;
double EarthSpeed;
boolean shouldContinue = true;
while (shouldContinue == true)
{
System.out.print(" What is the distance in feet:");
//ask the user to input variables
while (!keyboard.hasNextDouble())
{
System.out.println("Please enter a valid numeric value, try again: ");
keyboard.next();
}
Distance = keyboard.nextDouble();
System.out.print("Input the media: Air, Water, Steel, or Earth: ");
String Input = keyboard.next();
switch (Input.toLowerCase())
{
case "air":
AirSpeed = Distance / Air;
System.out.print("\n \nThe time to for sound to travel ");
System.out.print(Distance);
System.out.print(" feet through AIR" + "\n");
System.out.printf("%.6f", AirSpeed);
System.out.print(" seconds or ");
System.out.printf("%.1f", OneFootPerSecond * Air);
System.out.println(" miles per hour.");
break;
case "water":
WaterSpeed = Distance / Water;
System.out.print("\nThe time to for sound to travel ");
System.out.print(Distance);
System.out.print(" feet through WATER" + "\n");
System.out.printf("%.6f", WaterSpeed);
System.out.print(" seconds or ");
System.out.printf("%.1f", OneFootPerSecond * Water);
System.out.println(" miles per hour.");
break;
case "steel":
SteelSpeed = Distance / Steel;
System.out.print("\nThe time to for sound to travel ");
System.out.print(Distance);
System.out.print(" feet through STEEL" + "\n");
System.out.printf("%.6f", SteelSpeed);
System.out.print(" seconds or ");
System.out.printf("%.1f", OneFootPerSecond * Steel);
System.out.println(" miles per hour.");
break;
case "earth":
EarthSpeed = Distance / Water;
System.out.print("\nThe time to for sound to travel ");
System.out.print(Distance);
System.out.print(" feet through EARTH" + "\n");
System.out.printf("%.6f", EarthSpeed);
System.out.print(" seconds or ");
System.out.printf("%.1f", OneFootPerSecond * Earth);
System.out.println(" miles per hour.");
break;
default:
System.out.println("Invalid. Re-run the program. ");
break;
}
shouldContinue = promptForContinue(keyboard);
}
}
private static boolean promptForContinue(final Scanner keyboard)
{
boolean isValid = false;
String userInput = "";
do
{
System.out.print("Continue (Yes/No) ?");
userInput = keyboard.next();
isValid = userInput.matches("Yes|No");
if (!isValid)
{
System.out.println("\nInvalid entry.");
}
}
while (!isValid);
return userInput.equals("Yes") ? true : false;
}

You have a logic problem
System.out.print("\n \nEnter Yes for another calculation, else No: ");
Another = keyboard.next();
Another.toLowerCase();
if (Another.equals("yes")){
shouldContinue = false;
}
this code is going to exit the loop if the user type yes, your if should be something like:
if (Another.equals("yes")){
shouldContinue = true;
}
else
if (Another.equals("no")){
shouldContinue = false;
}
else
{
System.out.print("Invalid input");
shouldContinue = true;
}