Thread: Method Help

I'm creating three new methods in my code; getPrincipalAmount (acquire principal amount from the user and validate it) , getInterestRate (acquire interest rate from the user and validate it), getTerm (acquire term length from the user and validate it).

Basically the part I'm confused on is in the method how to ask the user and have them input it and then validate it. I currently don't have it set up to ask the user in the method, I'm unsure on how to do that part and just confused. Any help would be greatly appreciated, thanks!

import java.util.Scanner;
public class InterestCalculator5 {
	public static void main(String[] args )
	{
		Scanner input = new Scanner(System.in);
 
		String strAnsYesNo;
		char ansYesNo = 0;
 
 
			//Prompt user to enter loan amount
			System.out.print("Enter Loan Amount: ");
		    double principle = input.nextInt();
 
		    getPrincipalAmount(principle);
 
		    //Prompt user to enter interest rate
			System.out.print("Enter Yearly Interest Rate (1 to 100 percent): ");
		    double interest = input.nextDouble(); 
 
		    getInterestRate(interest);
 
		  //Prompt user to enter term 
		    System.out.print("Enter the Term (in months): ");
		    double term = input.nextInt();
 
		    getTerm(term);
 
 
		 int type=0;
			    			    //Prompt user to enter calculation type
			    			   do{System.out.print("Enter Interest Calculation Type (1 – Simple, 2 – Monthly Compounded, 3 – Daily Compounded):");
			    			    type = input.nextInt();
 
 
			    			   switch(type) 
			    			    {
			    			    case 1: displayInterest(principle,interest,term,"Simple",round((calculateSimpleInterest(principle, interest, term)),5),round((calculateSimpleInterest(principle, interest, term)+principle),2));
			    			    break;
 
			    			    case 2: displayInterest(principle,interest,term,"Compound Monthly", round(calculateCompoundInterest(principle, interest,term ,12.0 ),5), round((calculateCompoundInterest(principle, interest,term ,12.0)+principle),2));
			    			    break;
 
			    			    case 3: displayInterest(principle,interest,term,"Compound Daily", round(calculateCompoundInterest(principle, interest, term, 365.0 ),5), round((calculateCompoundInterest(principle, interest, term, 365.0)+principle),2));
			    			    break;
 
			    			    default: System.out.println("Calculation Type Error: You must select 1, 2 or 3. You entered " +type);
			    			    break;
 
			    			    }
		}while (ansYesNo =='y' || ansYesNo =='Y');
		System.out.println("Thank you for using Interest Calculator!");
	}
 
 
	/** Round **/
	  public static double round(double numb1, double numb2) {
	    double round = ((double) Math.round(numb1*(Math.pow(10, numb2)))/(Math.pow(10, numb2)));;
		return round;
	  }
 
	/** Calculate Simple **/
	  public static double calculateSimpleInterest(double numb1, double numb2, double numb3) {
	    double calculateSimpleInterest = ((numb1)*(numb2/100.0)*(numb3/12.0));
		return calculateSimpleInterest;
	  }
 
	  /** Calculate Compounded Daily **/
	  public static double calculateCompoundInterest(double numb1, double numb2, double numb3, double numb4 ) {
	     double calculateCompoundInterest = (numb1*Math.pow((1.0+((numb2/100.0)/numb4)),(numb4*(numb3/12.0))))-numb1;
		return calculateCompoundInterest;
	  }
 
	  /** display interest **/
	  public static void displayInterest(double numb1, double numb2, double numb3, String word1, double numb4, double numb5 ) {
 
 
		System.out.println("Principal Amount    Interest Rate    Term    Calculation Type    Calculated Interest    Total Repayment");
		System.out.println("----------------    -------------    ----    ----------------    -------------------    ---------------");
		System.out.print(numb1+"                ");
		System.out.print(+numb2+"           ");
		System.out.print(+numb3+"           ");
		System.out.print(word1+"            ");
		System.out.print(+numb4+"              ");
		System.out.println(+numb5);
	  }
 
	  /** Get principal amount **/
	  public static double getPrincipalAmount(double numb1) {
		  double getPrincipalAmount = 0;
		  do{if (numb1 > 0)
		  getPrincipalAmount = numb1;
		   		else{	
			    		System.out.println("Data Error: Loan amount must be greater than zero. You entered " +numb1);
		   		}		
			   }while (numb1 < 0);
		return getPrincipalAmount;
	  }
 
	  /** Get interest rate **/
	  public static double getInterestRate(double numb1) {
		  double getInterestRate = 0;
		  do{if (numb1 >= 0 && numb1 <= 100)
		  getInterestRate = numb1;
		   		else{	
			    		System.out.println("Data Error: Interest rate must be greater than or equal to zero and less than or equal to 100. You entered " +numb1);
		   		}		
			   }while (numb1 <= 0 && numb1 >= 100);
		return getInterestRate;
	  }
 
	  /** Get term **/
	  public static double getTerm(double numb1) {
		  double getTerm = 0;
		  do{if (numb1 > 0)
		  getTerm = numb1;
		   		else{	
			    		System.out.println("Data Error: Loan amount must be greater than zero. You entered " +numb1);
		   		}		
			   }while (numb1 < 0);
		return getTerm;
	  }
 
	  /** Get calculation type **/
	  public static double getCalculationType(double numb1) {
		  double getCalculationType = 0;
		  do{if (numb1 <1||numb1 >3)
			  getCalculationType = numb1;
		   		else{	
			    		System.out.println("Calculation Type Error: You must select 1, 2 or 3. You entered " +numb1);;
		   		}		
			   }while (numb1 > 1||numb1 < 3);
		return getCalculationType;
	  }
}

Originally Posted by Norm

The following statements from your posted code does that:

	System.out.print("Enter Loan Amount: ");    //  ask the user to enter data
	double principle = input.nextInt();           //  read the data that the user entered

Is there a way I can implement that in my method instead of having to ask that in the main?

When I do that

 /** Get principal amount **/
	  public static double getPrincipalAmount(double numb1) {
		  System.out.print("Enter Loan Amount: ");
		   double numb1 = input.nextdouble();
		  double getPrincipalAmount = 0;
		  do{if (numb1 > 0)
		  getPrincipalAmount = numb1;
		   		else{	
			    		System.out.println("Data Error: Loan amount must be greater than zero. You entered " +numb1);
		   		}		
			   }while (numb1 < 0);
		return getPrincipalAmount;
	  }

I get an error input cannot be resolved

Sorry, when I'm in the main and call the for the method, how would I make the method go ahead and ask for the principal amount instead of putting in the principal amount get in the method how would I know what to put in the ( ), of the getPrincipalAmount() to have the method just run?

Duplicate local variable numb1
input cannot be resolved

at InterestCalculator5.getPrincipalAmount(InterestCal culator5.java:59)
at InterestCalculator5.main(InterestCalculator5.java: 15)

Thanks for your help!

I have the getPrincipalAmount, getInterestRate, getCalculationType, and getTerm methods correct. I'm working on the askYesNo method now.. Also when the user enters in the data for getPrincipalAmount, getInterestRate, and getTerm I'm confused on how to use that entered data in the formulas I made methods for. Would I put those formulas in the getCalculationType method in an If statement if numb1==1 then it performs the simple interest calc.,2, 3 etc..

import java.util.Scanner;
public class InterestCalculator5 {
	public static void main(String[] args )
	{
		Scanner input = new Scanner(System.in);
		do{
 
		String strAnsYesNo;
		char ansYesNo = 0;
		getPrincipalAmount(1);
		getInterestRate(1);
		getTerm(1);
 
 
		} while (askYesNo("yes"));
 
	}
 
 
	/** Round **/
	  public static double round(double numb1, double numb2) {
	    double round = ((double) Math.round(numb1*(Math.pow(10, numb2)))/(Math.pow(10, numb2)));;
		return round;
	  }
 
	/** Calculate Simple **/
	  public static double calculateSimpleInterest(double numb1, double numb2, double numb3) {
	    double calculateSimpleInterest = ((numb1)*(numb2/100.0)*(numb3/12.0));
		return calculateSimpleInterest;
	  }
 
	  /** Calculate Compounded Daily **/
	  public static double calculateCompoundInterest(double numb1, double numb2, double numb3, double numb4 ) {
	     double calculateCompoundInterest = (numb1*Math.pow((1.0+((numb2/100.0)/numb4)),(numb4*(numb3/12.0))))-numb1;
		return calculateCompoundInterest;
	  }
 
	  /** display interest **/
	  public static void displayInterest(double numb1, double numb2, double numb3, String word1, double numb4, double numb5 ) {
 
 
		System.out.println("Principal Amount    Interest Rate    Term    Calculation Type    Calculated Interest    Total Repayment");
		System.out.println("----------------    -------------    ----    ----------------    -------------------    ---------------");
		System.out.print(numb1+"                ");
		System.out.print(+numb2+"           ");
		System.out.print(+numb3+"           ");
		System.out.print(word1+"            ");
		System.out.print(+numb4+"              ");
		System.out.println(+numb5);
	  }
 
	  /** Get principal amount **/
	  public static double getPrincipalAmount(double numb1) {
		  Scanner input = new Scanner(System.in);
		  double numb2 = 1;
		 do{System.out.print("Enter Loan Amount: ");
		   numb2 = input.nextDouble();
		   if(numb2 > 0);
 
		   		else{	
			    		System.out.println("Data Error: Loan amount must be greater than zero. You entered " +numb2);
		   		}		
			   }while (numb2 < 0);
		return numb2;
	  }
 
	  /** Get interest rate **/
	  public static double getInterestRate(double numb1) {
		  Scanner input = new Scanner(System.in);
		  double numb2=1;
		  do{System.out.print("Enter Yearly Interest Rate (1 to 100 percent): ");
		    numb2 = input.nextDouble(); 
		  double getInterestRate = 0;
		 if (numb2 >= 0 && numb2 <= 100)
		  getInterestRate = numb2;
		   		else{	
			    		System.out.println("Data Error: Interest rate must be greater than or equal to zero and less than or equal to 100. You entered " +numb2);
		   		}		
			   }while (numb2 <= 0 || numb2 >= 100);
		return numb2;
	  }
 
	  /** Get term **/
	  public static double getTerm(double numb1) {
		  Scanner input = new Scanner(System.in);
		  double numb2=1;
		  do{System.out.print("Enter the Term (in months): ");
		    numb2 = input.nextInt();
		  double getTerm = 0;
		  if (numb2 > 0)
		  getTerm = numb2;
		   		else{	
			    		System.out.println("Data Error: Loan amount must be greater than zero. You entered " +numb2);
		   		}		
			   }while (numb2 < 0);
		return numb2;
	  }
 
	  /** Get calculation type **/
	  public static double getCalculationType(double numb1) {
		  Scanner input = new Scanner(System.in);
		  int numb2=1;
		 do{ System.out.print("Enter Interest Calculation Type (1 – Simple, 2 – Monthly Compounded, 3 – Daily Compounded):");
		    numb2 = input.nextInt();
		  double getCalculationType = 0;
		  if (numb2 ==1|| numb2 ==2 || numb2==3)
			  getCalculationType = numb2;
		   		else{	
			    		System.out.println("Calculation Type Error: You must select 1, 2 or 3. You entered " +numb2);;
		   		}		
			   }while (numb2 !=1|| numb2!=2 || numb2 !=3);
		return numb2;
	  }
 
	  /**ask yes or no
	 * @return **/
	  public static boolean askYesNo( String a ) {
		  Scanner input = new Scanner(System.in);
		  String word1 = a;
		  char b='a';
		char word2 = b;
		  do{System.out.println("Calculate another loan interest (Yes/No)?");
			word1 = input.nextLine();
			if (word1.length() > 0)
				word2 = word1.charAt(0);
			if(word2!='y'&& word2!='Y'&& word2!='n'&& word2!='n')
			{
				System.out.println("Please enter 'Yes' or 'No'?");
			}
 
		}while(word2!='y'&& word2!='Y'&& word2!='n'&& word2!='n');
		return false;
 
	  }
}

I have a switch statement

 switch(type) 
			    			    {
			    			    case 1: displayInterest(principle,interest,term,"Simple",round((calculateSimpleInterest(principle, interest, term)),5),round((calculateSimpleInterest(principle, interest, term)+principle),2));
			    			    break;
 
			    			    case 2: displayInterest(principle,interest,term,"Compound Monthly", round(calculateCompoundInterest(principle, interest,term ,12.0 ),5), round((calculateCompoundInterest(principle, interest,term ,12.0)+principle),2));
			    			    break;
 
			    			    case 3: displayInterest(principle,interest,term,"Compound Daily", round(calculateCompoundInterest(principle, interest, term, 365.0 ),5), round((calculateCompoundInterest(principle, interest, term, 365.0)+principle),2));
			    			    break;
 
			    			    default: System.out.println("Calculation Type Error: You must select 1, 2 or 3. You entered " +type);
			    			    break;

Is there a certain way I need to save the users input to use for the other methods

I'm just confused on how to take the users input for the principal amount, interest rate, and term to the other method..

 /** Get calculation type **/
	  public static double getCalculationType(double numb1) {
		  Scanner input = new Scanner(System.in);
		  int numb2=1;
 
		 do{ System.out.print("Enter Interest Calculation Type (1 – Simple, 2 – Monthly Compounded, 3 – Daily Compounded):");
		    numb2 = input.nextInt();
		    double principle = 10;
			  double interest=10;
			  double term=10;
		    switch(numb2) 
		    {
		    case 1: displayInterest(principle,interest,term,"Simple",round((calculateSimpleInterest(principle, interest, term)),5),round((calculateSimpleInterest(principle, interest, term)+principle),2));
		    break;
 
		    case 2: displayInterest(principle,interest,term,"Compound Monthly", round(calculateCompoundInterest(principle, interest,term ,12.0 ),5), round((calculateCompoundInterest(principle, interest,term ,12.0)+principle),2));
		    break;
 
		    case 3: displayInterest(principle,interest,term,"Compound Daily", round(calculateCompoundInterest(principle, interest, term, 365.0 ),5), round((calculateCompoundInterest(principle, interest, term, 365.0)+principle),2));
		    break;
 
		    default: System.out.println("Calculation Type Error: You must select 1, 2 or 3. You entered " +numb2);
		    break;
		    }
			   }while (numb2 !=1|| numb2!=2 || numb2 !=3);
		return numb2;
	  }