Section 2

src/main/java/com/b/simple/design/business/customer/CustomerBOImpl.java

@@ -11,33 +11,28 @@
 
 public class CustomerBOImpl implements CustomerBO {
 
-	@Override
-	public Amount getCustomerProductsSum(List<Product> products)
-			throws DifferentCurrenciesException {
-		BigDecimal temp = BigDecimal.ZERO;
-
-		if (products.size() == 0)
-			return new AmountImpl(temp, Currency.EURO);
-
-		// Throw Exception If Any of the product has a currency different from
-		// the first product
-		Currency firstProductCurrency = products.get(0).getAmount()
-				.getCurrency();
-
-		for (Product product : products) {
-			boolean currencySameAsFirstProduct = product.getAmount()
-					.getCurrency().equals(firstProductCurrency);
-			if (!currencySameAsFirstProduct) {
-				throw new DifferentCurrenciesException();
-			}
-		}
-
-		// Calculate Sum of Products
-		for (Product product : products) {
-			temp = temp.add(product.getAmount().getValue());
-		}
-
-		// Create new product
-		return new AmountImpl(temp, firstProductCurrency);
-	}
+    @Override
+    public Amount getCustomerProductsSum(List<Product> products) throws DifferentCurrenciesException {
+        if (products.isEmpty()) {
+            return new AmountImpl(BigDecimal.ZERO, Currency.EURO);
+        }
+        Currency firstProductCurrency = products.get(0).getAmount().getCurrency();
+        if (!doAllProductsHaveSameCurrency(products, firstProductCurrency)) {
+            throw new DifferentCurrenciesException();
+        }
+
+        return new AmountImpl(calculateSumOfProducts(products), firstProductCurrency);
+    }
+
+    private static BigDecimal calculateSumOfProducts(List<Product> products) {
+        return products.stream()
+                .map(product -> product.getAmount().getValue())
+                .reduce(BigDecimal.ZERO, BigDecimal::add);
+    }
+
+    private static boolean doAllProductsHaveSameCurrency(List<Product> products, Currency currency) {
+        return products.stream()
+                .map(product -> product.getAmount().getCurrency())
+                .allMatch(productCurrency -> productCurrency.equals(currency));
+    }
 }

src/main/java/com/b/simple/design/business/student/StudentHelper.java

@@ -1,66 +1,71 @@
 package com.b.simple.design.business.student;
+
 public class StudentHelper {
 
-	/* PROBLEM 1 */	
-	/*
-	* You get a grade B if marks are between 51 and 80 (both inclusive). Except for Maths where the upper limit is increased by 10.
-	*/
-	public boolean isGradeB(int marks, boolean isMaths) {
-		return isMaths ? marks>=51 && marks<=90 : marks>=51 && marks<=80; 
-	}
+    public static final int GRADE_B_UPPER_LIMIT = 80;
+    public static final int GRADE_B_LOWER_LIMIT = 51;
+    public static final int EXTRA_FOR_MATH = 10;
+
+    /* PROBLEM 1 */
+    /*
+     * You get a grade B if marks are between 51 and 80 (both inclusive).
+     * Except for Maths where the upper limit is increased by 10.
+     */
+    public boolean isGradeB(int marks, boolean isMaths) {
+        int extraLimit = isMaths ? EXTRA_FOR_MATH : 0;
+        int upperLimit = GRADE_B_UPPER_LIMIT + extraLimit;
+        return marks >= GRADE_B_LOWER_LIMIT && marks <= upperLimit;
+    }
 
-	/* PROBLEM 2 */
+    /* PROBLEM 2 */
 	/*
 	You are awarded a grade based on your marks.
 	Grade A = 91 to 100, Grade B = 51 to 90, Otherwise Grade C
 	Except for Maths where marks to get a Grade are 5 higher than required for other subjects.
 	*/
 
-	public String getGrade(int mark, boolean isMaths) {
-		String grade = "C";
-
-		if (isGradeA(mark, isMaths))
-			grade = "A";
-		else if (isBGrade(mark, isMaths)) {
-			grade = "B";
-		}
-		return grade;
-	}
+    public String getGrade(int mark, boolean isMaths) {
+        int extraLimit = isMaths ? 5 : 0;
 
-	private boolean isGradeA(int mark, boolean isMaths) {
-		int lowerLimitForAGrade = isMaths ? 95
-				: 90;
-		return mark > lowerLimitForAGrade;
-	}
-
-	private boolean isBGrade(int mark, boolean isMaths) {
-		int lowerLimitGradeB = isMaths ? 55
-				: 50;
-		return mark > lowerLimitGradeB && mark < 90;
-	}
+        if (mark >= 91 + extraLimit) {
+            return "A";
+        }
+        if (mark >= 51 + extraLimit) {
+            return "B";
+        }
+        return "C";
+    }
 
     /*  PROBLEM 3
      * You and your Friend are planning to enter a Subject Quiz.
      * However, there is a marks requirement that you should attain to qualify.
-     * 
+     *
      * Return value can be YES, NO or MAYBE.
-     * 
+     *
      * YES If either of you are very good at the subject(has 80 or more marks)
      * However, there is an exception that if either of you is not good in the subject(20 or less marks), it is NO.
      * In all other conditions, return MAYBE.
-     * 
+     *
      * However, the definition for good and not good are 5 marks higher if the subject is Mathematics.
-     * 
+     *
      * marks1 - your marks
      * marks2 - your friends marks
-    */
-        
+     */
+
     public String willQualifyForQuiz(int marks1, int marks2, boolean isMaths) {
-        if ((isMaths ? marks1 <= 25 : marks1 <= 20)
-                || (isMaths ? marks2 <= 25 : marks2 <= 20)) return "NO";
-        if ((isMaths ? marks1 >= 85 : marks1 >= 80)
-                || (isMaths ? marks2 >= 85 : marks2 >= 80)) return "YES";
+        if (isNotGood(marks1, isMaths) || isNotGood(marks2, isMaths)) return "NO";
+        if (isGood(marks1, isMaths) || isGood(marks2, isMaths)) return "YES";
         return "MAYBE";
-    }	
+    }
+
+    private static boolean isGood(int marks, boolean isMaths) {
+        int extraLimit = isMaths ? 5 : 0;
+        return marks >= 80 + extraLimit;
+    }
+
+    private static boolean isNotGood(int marks, boolean isMaths) {
+        int extraLimit = isMaths ? 5 : 0;
+        return  marks <= 20 + extraLimit;
+    }
 
 }

src/main/java/com/b/simple/design/business/text/TextHelper.java

@@ -2,11 +2,75 @@
 
 public class TextHelper {
 
-	public String swapLastTwoCharacters(String str) {
-		return null;
-	}
+    public String swapLastTwoCharactersMine(String str) {
+		int len = str.length();
+        if (len <= 1) {
+            return str;
+        }
 
-	public String truncateAInFirst2Positions(String str) {
-		return null;
-	}
+        StringBuilder res = new StringBuilder();
+		res.append(str, 0, len - 2);
+		char lastCharacter = str.charAt(len - 1);
+		char prevLast = str.charAt(len - 2);
+		res.append(lastCharacter);
+		res.append(prevLast);
+
+        return res.toString();
+    }
+
+    public String swapLastTwoCharacters(String str) {
+        int len = str.length();
+        if (len <= 1) {
+            return str;
+        }
+        char lastCharacter = str.charAt(len - 1);
+        char prevLast = str.charAt(len - 2);
+
+        String restOfString = str.substring(0, len - 2);
+
+        return restOfString + lastCharacter + prevLast;
+    }
+
+    public String truncateAInFirst2PositionsAttempt1(String str) {
+        int len = str.length();
+        if (len == 0) {
+            return str;
+        }
+        StringBuilder res = new StringBuilder();
+        char firstCharacter = str.charAt(0);
+        if (firstCharacter != 'A') {
+            res.append(firstCharacter);
+        }
+        if (len >= 2) {
+            char secondCharacter = str.charAt(2);
+             if (secondCharacter != 'A') {
+                 res.append(secondCharacter);
+             }
+        }
+        if (len >= 3) {
+            String restOfString = str.substring(3);
+            res.append(restOfString);
+        }
+
+        return res.toString();
+    }
+
+    public String truncateAInFirst2PositionsAttempt2(String str) {
+        if (str.length() <= 2) {
+            return str.replaceAll("^A+", "");
+        }
+        String firstTwo = str.substring(0, 2).replaceAll("A", "");
+        return firstTwo + str.substring(2);
+    }
+
+    public String truncateAInFirst2Positions(String str) {
+        if (str.length() <= 2) {
+            return str.replaceAll("A", "");
+        }
+        String firstTwo = str.substring(0, 2);
+        String firstTwoCharactersRemoved = firstTwo.replaceAll("A", "");
+        String restOfTheString = str.substring(2);
+
+        return firstTwoCharactersRemoved + restOfTheString;
+    }
 }

src/main/java/com/c/refactoring/movie/Movie.java

@@ -2,10 +2,18 @@
 
 import com.c.refactoring.StringUtils;
 
+import java.util.HashSet;
+import java.util.Set;
+
 public class Movie {
 
     String rating;
-
+    private static final Set<String> VALID_B_RATING = new HashSet<String>() {{
+        add("B1");
+        add("B2");
+        add("B3");
+        add("B4");
+    }};
     public Movie(String rating) {
         super();
         this.rating = rating;
@@ -19,21 +27,21 @@ public String getRating() {
     Where x represents any digit between 0 and 9, and y represents 
     any digit between 1 and 4*/
     public boolean isValidRating() {
-        if (this.getRating() != null) {
-            if (this.getRating().substring(0, 1).equalsIgnoreCase("B")
-                    && this.getRating().length() == 2) {
-                if (StringUtils.isNumeric(this.getRating().substring(1, 2))
-                        && Integer.parseInt(this.getRating().substring(1, 2)) > 0
-                        && Integer.parseInt(this.getRating().substring(1, 2)) < 5)
-                    return true;
-
-            } else if (this.getRating().substring(0, 1).equalsIgnoreCase("A")
-                    && this.getRating().length() == 3
-                    && StringUtils.isNumeric(this.getRating().substring(1, 3)))
-                return true;
-
+        if (getRating() == null) {
+            return false;
         }
-        return false;
+        return isValidBRating() || isValidARating();
+    }
+
+    private boolean isValidBRating() {
+        return VALID_B_RATING.contains(getRating());
+    }
+
+    private boolean isValidARating() {
+        String rating = this.getRating();
+        String firstCharacter = rating.substring(0, 1);
+        return firstCharacter.equalsIgnoreCase("A")
+                && rating.length() == 3 && StringUtils.isNumeric(rating.substring(1, 3));
     }
 
     public void setRating(String rating) {