import java.util.Scanner;

/**

* A program that performs basic calculations for the user.

* It currently contains many errors.

*

* @author Chad Hogg

*/

public class Calculator {

/**

* Performs an arithmetic operation.

*

* @param firstOperand The first number to operate on.

* @param secondOperand The second number to operate on.

* @param operation Either "+", "-", "*", or "/".

* @return The result of the operation.

*/

public static double calculate(double firstOperand, double secondOperand, String operation) {

if(!operation.equals("+") && !operation.equals("-") && !operation.equals("*") && !operation.equals("/")) {

throw new IllegalArgumentException("The operation must be +, -, *, or /.");

}

double result = 0.0;

if(operation == "+") {

result = firstOperand + secondOperand;

}

if(operation == "-") {

result = firstOperand - secondOperand;

}

if(operation == "*") {

result = firstOperand * secondOperand;

}

else if(operation == "/")

result = firstOperand / secondOperand;

return result;

}

/**

* Gets the special name of an operand based on the operator and its position.

* The rules follow the table below:

* 1st 2nd

* + augend addend

* - minuend subtrahend

* * multiplicand multiplier

* / dividend divisor

*

* @param operator Either +, -, *, or /.

* @param isFirst Whether or not we are looking for the name of the first operand.

* @return The name of the operand.

*/

public static String getOperandName(String operator, boolean isFirst) {

String answer = "operand";

if(operator == "+") {

if(isFirst) {

answer = "Augend";

}

else {

answer = "Addend";

}

}

else if(operator == "-") {

if(isFirst) {

answer = "Minuend";

}

else {

answer = "Subtrahend";

}

}

else if(operator == "*") {

if(isFirst) {

answer = "Multiplicand";

}

else {

answer = "Multiplier";

}

}

else if(operator == "/") {

if(isFirst) {

answer = "Dividend";

}

else {

answer = "Divisor";

}

}

else {

throw new IllegalArgumentException("Operator must be +, -, *, or /.");

}

return answer;

}

{

}

/**

* Asks the user what operation to do.

* Repeats the question until it gets an operation

*

* @param console A Scanner from which we can read input.

* @return The operator that the user chose, either "+", "-", "*", or "/".

*/

public static String getOperation(Scanner console) {

System.out.print("Enter +, -, *, or /: ");

String operation = console.next();

while(!operation.equals("+") && !operation.equals("-") && !operation.equals("*") && !operation.equals("/")) {

System.out.println("Please try again.");

System.out.print("Enter +, -, *, or /: ");

operation = console.next();

}

return operation;

}

/**

* Asks the user for a number.

*

* @param console A Scanner from which we can read input.

* @param prompt The String that should be printed to prompt the user.

* @return The number that the user typed in.

*/

public static double getDouble(Scanner console, String prompt) {

System.out.print(prompt);

while(!console.hasNextDouble()) {

System.out.println("That is not a number.");

System.out.print(prompt);

console.next();

}

double answer = console.nextDouble();

return answer;

}

/**

* Runs the calculator program.

*

* @param console A Scanner from which we can get user input.

*/

public static void runProgram(Scanner console) {

String doAgain = "no";

while(!doAgain.equals("no"));

if(doAgain.equals("yes")) {

String operation = getOperation(console);

double firstOperand = getDouble(console, getOperandName(operation, true) + ": ");

double secondOperand = getDouble(console, getOperandName(operation, true) + ": ");

double answer = calculate(firstOperand, firstOperand, operation);

System.out.println(firstOperand + " " + operation + " " + secondOperand + " = " + answer);

}

else {

System.out.println("That was not an acceptable answer.");

System.out.print("Would you like to do another calculation?: ");

doAgain = console.next();

}

System.out.println("Goodbye!");

}

/**

* Runs tests to ensure that the calculate method works correctly.

*/

public static void testCalculate() {

double expectedAnswer;

double receivedAnswer;

receivedAnswer = calculate(10.0, 7.0, "+");

expectedAnswer = 17.0;

System.out.println("First test should have been " + expectedAnswer + " was " + receivedAnswer);

receivedAnswer = calculate(10.0, 5.3, "-");

expectedAnswer = 4.7;

System.out.println("Second test should have been " + expectedAnswer + " was " + receivedAnswer);

receivedAnswer = calculate(5.0, 3.0, "*");

expectedAnswer = 15.0;

System.out.println("Third test should have been " + expectedAnswer + " was " + receivedAnswer);

receivedAnswer = calculate(27.0, 9.0, "/");

expectedAnswer = 3.0;

System.out.println("Fourth test should have been " + expectedAnswer + " was " + receivedAnswer);

receivedAnswer = calculate(27.0, 9.0, "#");

}

public static void testGetOperandName() {

String receivedAnswer;

String expectedAnswer;

receivedAnswer = getOperandName("+", true);

expectedAnswer = "Augend";

System.out.println("First test should have been " + expectedAnswer + " was " + receivedAnswer);

receivedAnswer = getOperandName("+", false);

expectedAnswer = "Addend";

System.out.println("Second test should have been " + expectedAnswer + " was " + receivedAnswer);

receivedAnswer = getOperandName("-", true);

expectedAnswer = "Minuend";

System.out.println("Third test should have been " + expectedAnswer + " was " + receivedAnswer);

receivedAnswer = getOperandName("-", false);

expectedAnswer = "Subtrahend";

System.out.println("Fourth test should have been " + expectedAnswer + " was " + receivedAnswer);

receivedAnswer = getOperandName("*", true);

expectedAnswer = "Multiplicand";

System.out.println("Fifth test should have been " + expectedAnswer + " was " + receivedAnswer);

receivedAnswer = getOperandName("*", false);

expectedAnswer = "Multiplier";

System.out.println("Sixth test should have been " + expectedAnswer + " was " + receivedAnswer);

receivedAnswer = getOperandName("/", true);

expectedAnswer = "Dividend";

System.out.println("Seventh test should have been " + expectedAnswer + " was " + receivedAnswer);

receivedAnswer = getOperandName("/", false);

expectedAnswer = "Divisor";

System.out.println("Eighth test should have been " + expectedAnswer + " was " + receivedAnswer);

receivedAnswer = getOperandName("$", true);

}

/**

* Runs the program.

*

* @param args Not yet explained or used.

*/

public static void main(String[] args) {

Scanner console = new Scanner(System.in);

runProgram(console);

}

}

Looking specifically at the "runProgram" method, it is not working properly and I do not know why that is.