Fixed while loop bug fix in LoanInput and refactored code

src/main/java/org/keith/core/Amortization.java

@@ -5,7 +5,6 @@
 import java.lang.Math;
 import java.text.DecimalFormat;
 import java.text.NumberFormat;
-import java.util.Scanner;
 
 public class Amortization extends LoanDetails {
     private final int ifFavorable = 35,
@@ -17,12 +16,13 @@ public class Amortization extends LoanDetails {
                          adequate = "Adequate",
                          highRisk = "High Risk!",
                         yes = "Y",
-                        no = "N";
-    private final String valueFormat = "0.##";
-    private final String ANSI_RESET = "\u001B[0m",
-                         ANSI_GREEN = "\u001B[32m",
-                         ANSI_RED = "\u001B[31m",
-                         ANSI_YELLOW = "\u001B[33m";
+                        no = "N",
+                        scheduleNeedInput = "Do you want a Schedule(Y/N): ",
+                        valueFormat = "0.##",
+                        ANSI_RESET = "\u001B[0m",
+                        ANSI_GREEN = "\u001B[32m",
+                        ANSI_RED = "\u001B[31m",
+                        ANSI_YELLOW = "\u001B[33m";
     private String input;
     LoanDetails loanDetails = new LoanDetails();
 
@@ -55,7 +55,7 @@ private void checkIfSchedulerNeeded(){
                                             loanDetails.getAnnualInterestRate(),
                                             loanDetails.getNumberPayment());
         Menu menu = new Menu();
-        getInput();
+        input = getInput();
 
         switch (input.toUpperCase()){
             case yes -> scheduler.getTable();
@@ -82,11 +82,9 @@ public String formatToTwoDigits(Double value){
         return df.format(value);
     }
 
-    private void getInput(){
+    private String getInput(){
         SingletonScanner singletonScanner = SingletonScanner.getInstance();
-        Scanner scanner = singletonScanner.getScanner();
-        System.out.print("Do you want a Schedule(Y/N): ");
-        input = scanner.nextLine();
+        return singletonScanner.getString(scheduleNeedInput);
     }
 
     public Double calculateInterestInDecimals(){

src/main/java/org/keith/core/LoanInput.java

@@ -1,44 +1,40 @@
 package org.keith.core;
-import java.util.Scanner;
 
 public class LoanInput{
     private Integer principle ,
                     terms,
                     paymentAmount,
                     grossIncome;
     private Double interest;
-    private boolean isRunningterms  = true;
+    private final String paymentAmountInput =  "Number of payments in a single year: ",
+                         principleInput = "Loan amount: ",
+                         termsInput =  "Terms(year): ",
+                         grossIncomeInput = "Gross income: ",
+                         interestInput = "Interest rate: ";
+    private boolean isRunningTerms = true;
     SingletonScanner singletonScanner = SingletonScanner.getInstance();
-    Scanner scanner = singletonScanner.getScanner();
 
 //     Check Terms based on the type of loan
     private void checkTerms(Integer maxTerms){
-        while(isRunningterms) {
-            if (mustBeLessThanMaxTerms(maxTerms)) {
-                paymentAmount = getPaymentAmount();
-                isRunningterms = false;
-            } else if(ifGreaterThanMaxTerms(maxTerms)){
-                System.out.println("Maximum allowed term is " + maxTerms + " years");
-                terms = getTermsAmount();
+        while(isRunningTerms) {
+            terms = getTermsAmount();
+
+            if(checkIfLessThanMaxTerms(maxTerms)){
+                break;
             }
-//                break;
         }
     }
 
-    private Boolean mustBeLessThanMaxTerms(Integer maxTerms){
+    private Boolean checkIfLessThanMaxTerms(Integer maxTerms){
         return terms <= maxTerms;
     }
 
-    private Boolean ifGreaterThanMaxTerms(Integer maxTerms){
-        return terms >= maxTerms;
-    }
-
     public void getLoanInfo(Integer maxTerms){
+        System.out.println("Enter your loan information.");
         principle = getPrincipleAmount();
-        terms = getTermsAmount();
         checkTerms(maxTerms);
 
-
+        paymentAmount = getPaymentAmount();
         interest = getInterest();
         grossIncome = getGrossIncome();
         Amortization amortization = new Amortization(principle,
@@ -50,31 +46,30 @@ public void getLoanInfo(Integer maxTerms){
     }
 
     private Integer getPrincipleAmount(){
-        System.out.print("""
-                Enter your loan information.
-                Loan amount:\s""");
-        return Integer.parseInt(scanner.nextLine());
+        return parseInteger(singletonScanner.getString(principleInput));
     }
 
     private Integer getTermsAmount(){
-        System.out.print("Terms(year): ");
-        return Integer.parseInt(scanner.nextLine());
+        return parseInteger(singletonScanner.getString(termsInput));
     }
 
     private Integer getPaymentAmount(){
-        System.out.print("Number of payments in a single year: ");
-        return Integer.parseInt(scanner.nextLine());
+        return parseInteger(singletonScanner.getString(paymentAmountInput));
     }
 
     private Double getInterest(){
-        System.out.print("Interest rate: ");
-        return Double.parseDouble(scanner.nextLine());
+        return parseDouble(singletonScanner.getString(interestInput));
     }
 
     private Integer getGrossIncome(){
+        return parseInteger(singletonScanner.getString(grossIncomeInput));
+    }
+
+    private Integer parseInteger(String value){
+        return Integer.parseInt(value);
+    }
 
-        System.out.print("Gross income: ");
-        return Integer.parseInt(scanner.nextLine());
-//        scanner.nextLine();
+    private Double parseDouble(String value){
+        return Double.parseDouble(value);
     }
 }

src/main/java/org/keith/core/Scheduler.java

@@ -9,8 +9,8 @@ public class Scheduler{
     private Integer principle;
     private Integer endPeriod,
                     numberPayment;
-    private Double monthlyPayments;
-    private Double balance,
+    private Double monthlyPayments,
+                   balance,
                    annualInterest,
                    periodInterest,
                    principlePaid = 0.0,
@@ -33,9 +33,12 @@ protected void getTable(){
         balance = convertToDouble(principle);
         periodInterest = calculatePeriodInterest(annualInterest, numberPayment);
         for(int period = startPeriod; period <= endPeriod; period++){
-            interestPaid = balance * periodInterest;
-            principlePaid = monthlyPayments - interestPaid;
-            balance -= principlePaid;
+//            interestPaid = balance * periodInterest;
+            interestPaid = calculateInterestPaid();
+//            principlePaid = monthlyPayments - interestPaid;
+            principlePaid = calculatePrinciplePaid();
+//            balance -= principlePaid;
+            balance = calculateNewBalance();
             System.out.println("Period: " + period + ", Principle: " + formatToCurrency(principlePaid) + ", Interest: " + formatToCurrency(interestPaid) + ", Balance: " + formatToCurrency(balance));
         }
         System.out.println("Monthly Payment: " + formatToCurrency(monthlyPayments));
@@ -63,4 +66,15 @@ private String formatToCurrency(Double value){
         NumberFormat cf = NumberFormat.getCurrencyInstance();
         return cf.format(value);
     }
+
+    private Double calculateInterestPaid(){
+        return balance * periodInterest;
+    }
+
+    private Double calculatePrinciplePaid(){
+        return monthlyPayments - interestPaid;
+    }
+    private Double calculateNewBalance(){
+        return balance -= principlePaid;
+    }
 }

src/main/java/org/keith/core/SingletonScanner.java

@@ -5,20 +5,26 @@
 
 public class SingletonScanner{
     private static SingletonScanner instance = null;
-    private static Scanner scanner = null;
+    private Scanner scanner;
 
-    private SingletonScanner() {}
+    // Guarantees that no scanner object can be created outside SingletonScanner class
+    private SingletonScanner() {
+            scanner = new Scanner(System.in);
+            scanner.useLocale(Locale.US); // makes . for decimal input possible
+    }
 
     public static SingletonScanner getInstance() {
         if (instance == null) {
             instance = new SingletonScanner();
-            scanner = new Scanner(System.in);
-            scanner.useLocale(Locale.US);
         }
         return instance;
     }
 
-    public Scanner getScanner() {
-        return scanner;
+    public String getString(String sPrompt) {
+        System.out.print(sPrompt);
+        scanner.useDelimiter("\r\n"); // Setting this delimiter ensures that we capture everything up to the <Enter> key. Without this, input stops at the next whitespace (space, tab, newline etc.).
+        String sInput = scanner.nextLine();
+        scanner.reset(); // The preceding use of useDelimiter() changed the state of the Scanner object. reset() re-establishes the original state.
+        return sInput;
     }
 }

src/main/java/org/keith/menu/Menu.java

@@ -3,7 +3,6 @@
 import org.keith.core.LoanInput;
 import org.keith.core.SingletonScanner;
 import org.keith.menu.enums.MenuCommand;
-import java.util.Scanner;
 
 public class Menu {
     private final String MENU = """
@@ -25,7 +24,7 @@ public void LOGO() {
                 """);
     }
     public final String WELCOME_MSG = """
-    LOAN CLI v1.0.2
+    LOAN CLI v1.0.3
     © Keith Atmodimedjo
     Type "help" to list command options.
     """;
@@ -42,9 +41,9 @@ public void LOGO() {
     LoanInput mi = new LoanInput();
 
     public void getMenuInput(){
-        while(isRunning){
+        MAIN_LOOP:while(isRunning){
             try {
-                getInput();
+                input = getInput();
 
                 // if input is empty continue to print the option number message above
                 if (ifInputIsEmpty()) {
@@ -57,7 +56,9 @@ public void getMenuInput(){
                     case MORTGAGE -> mi.getLoanInfo(maxMortgageTerms);
                     case CAR -> mi.getLoanInfo(maxVehicleTerms);
                     case HELP -> showMenu();
-                    case EXIT -> isRunning = false;
+                    case EXIT -> {
+                        break MAIN_LOOP;
+                    }
                     default -> getInput();
                 }
 
@@ -85,10 +86,8 @@ private void showMenu(){
         System.out.print(MENU);
     }
 
-    public void getInput(){
+    public String getInput(){
         SingletonScanner singletonScanner = SingletonScanner.getInstance();
-        Scanner scanner = singletonScanner.getScanner();
-        System.out.print(cmdLine);
-        input = scanner.nextLine();
+        return singletonScanner.getString(cmdLine);
     }
 }