all tests pass

src/main/java/rocks/zipcode/quiz4/arrays/ArrayUtils.java

@@ -1,22 +1,46 @@
 package rocks.zipcode.quiz4.arrays;
 
+import java.util.Arrays;
+import java.util.Stack;
+
 /**
  * @author leon on 01/01/2019.
  */
 public class ArrayUtils {
     public static String getMiddleElement(String[] values) {
-        return null;
+        return values[values.length/2];
+    }
+
+    public static String[] addElement(String[] arr, String str){
+        String[] result = new String[arr.length+1];
+        int counter = 0;
+        for(String existing : arr){
+            result[counter] = existing;
+            counter++;
+        }
+        result[result.length-1] = str;
+        return result;
     }
 
     public static String[] removeMiddleElement(String[] values) {
-        return null;
+        String[] answer = new String[0];
+        for (int i = 0; i < values.length;i++){
+            if (i!= values.length/2){
+                answer = addElement(answer,values[i]);
+            }
+        }
+        return answer;
     }
 
     public static String getLastElement(String[] values) {
-        return null;
+        return values[values.length-1];
     }
 
     public static String[] removeLastElement(String[] values) {
-        return null;
+        String[] result = new String[values.length-1];
+        for(int i = 0;i<values.length-1;i++){
+            result[i] = values[i];
+        }
+        return result;
     }
 }

src/main/java/rocks/zipcode/quiz4/collections/WordCounter.java

@@ -1,12 +1,20 @@
 package rocks.zipcode.quiz4.collections;
 
-import java.util.Map;
+import java.util.*;
+import java.util.function.Function;
+import java.util.stream.Collectors;
 
 public class WordCounter {
+    HashMap<String, Integer> countMap;
+
     public WordCounter(String... strings) {
+        this.countMap = new HashMap<>();
+        for(String str : strings){
+            countMap.put(str,Collections.frequency(Arrays.asList(strings),str));
+        }
     }
 
     public Map<String, Integer> getWordCountMap() {
-        return null;
+        return this.countMap;
     }
 }

src/main/java/rocks/zipcode/quiz4/collections/culonary/Curry.java

@@ -1,4 +1,14 @@
 package rocks.zipcode.quiz4.collections.culonary;
 
-public class Curry {
-}
+public class Curry implements Spice{
+    String name = "Curry";
+
+    public String getName(){
+        return this.name;
+    }
+
+    public void setName(String name) {
+        this.name = name;
+    }
+
+}

src/main/java/rocks/zipcode/quiz4/collections/culonary/Food.java

@@ -1,20 +1,36 @@
 package rocks.zipcode.quiz4.collections.culonary;
 
-import java.util.List;
-import java.util.Map;
+import java.util.*;
+import java.util.function.Function;
+import java.util.stream.Collectors;
 
 /**
  * @author leon on 27/12/2018.
  */
 public class Food {
-    public List<Spice> getAllSpices() {
-        return null;
+    ArrayList<Spice> added;
+
+    public Food(){
+        this.added = new ArrayList<Spice>();
+
+    }
+    public List getAllSpices() {
+        return added;
     }
 
     public <SpiceType extends Class<? extends Spice>> Map<SpiceType, Integer> getSpiceCount() {
-        return null;
+        HashMap<SpiceType, Integer> spiceMap = new HashMap<>();
+        for(Spice currentSpice : added){
+    //achieved casting w/ help from classmate
+            SpiceType spice = (SpiceType)currentSpice.getClass();
+            spiceMap.put(spice,added.size());
+        }
+        System.out.println(spiceMap.keySet());
+
+        return spiceMap;
     }
 
     public void applySpice(Spice spice) {
+        added.add(spice);
     }
 }

src/main/java/rocks/zipcode/quiz4/collections/culonary/Ginger.java

@@ -3,5 +3,16 @@
 /**
  * @author leon on 27/12/2018.
  */
-public class Ginger {
+public class Ginger implements Spice{
+    String name = "Ginger";
+
+
+    public String getName(){
+        return this.name;
+    }
+
+    public void setName(String name) {
+        this.name = name;
+    }
+
 }

src/main/java/rocks/zipcode/quiz4/collections/culonary/Pepper.java

@@ -3,5 +3,14 @@
 /**
  * @author leon on 27/12/2018.
  */
-public class Pepper {
-}
+public class Pepper implements Spice{
+    String name = "Pepper";
+
+
+    public String getName() {
+        return this.name;
+    }
+
+    public void setName(String name) {
+        this.name = name;
+    }}

src/main/java/rocks/zipcode/quiz4/collections/culonary/Spice.java

@@ -4,4 +4,5 @@
  * @author leon on 27/12/2018.
  */
 public interface Spice {
+
 }

src/main/java/rocks/zipcode/quiz4/fundamentals/Calculator.java

@@ -1,35 +1,37 @@
 package rocks.zipcode.quiz4.fundamentals;
 
+import java.util.Arrays;
+
 /**
  * @author leon on 21/12/2018.
  */
 public class Calculator {
     public static Double squareRoot(Double value) {
-        return null;
+        return Math.sqrt(value);
     }
 
     public static Double square(Double value) {
-        return null;
+        return Math.pow(value,2);
     }
 
     public static Double[] squareRoots(Double... value) {
-        return null;
+        return Arrays.stream(value).map(x -> x = squareRoot(x)).toArray(Double[]::new);
     }
 
     public static Double[] squares(Double... values) {
-        return null;
+        return Arrays.stream(values).map(x -> x = square(x)).toArray(Double[]::new);
     }
 
     public static Double add(Double value1, Double value2) {
-        return null;
+        return value1 + value2;
     }
 
     public static Double subtract(Double value1, Double value2) {
-        return null;
+        return value1 - value2;
     }
 
 
     public static Double divide(Double divisor, Double dividend) {
-        return null;
+        return divisor/dividend;
     }
 }

src/main/java/rocks/zipcode/quiz4/fundamentals/StringUtils.java

@@ -1,34 +1,98 @@
 package rocks.zipcode.quiz4.fundamentals;
 
+import java.util.Arrays;
+import java.util.stream.Collectors;
+import java.util.stream.IntStream;
+
 /**
  * @author leon on 21/12/2018.
  */
 public class StringUtils {
     public static Character getMiddleCharacter(String string) {
-        return null;
+        return string.toCharArray()[string.length()/2];
     }
 
     public static String capitalizeMiddleCharacter(String str) {
-        return null;
+        char[] letters = str.toCharArray();
+        letters[letters.length/2] = getMiddleCharacter(str).toString().toUpperCase().toCharArray()[0];
+        String result = "";
+        for(char letter : letters){
+            result += letter;
+        }
+        return result;
     }
 
     public static String lowerCaseMiddleCharacter(String str) {
-        return null;
+        char[] letters = str.toCharArray();
+        letters[letters.length/2] = getMiddleCharacter(str).toString().toLowerCase().toCharArray()[0];
+        String result = "";
+        for(char letter : letters){
+            result += letter;
+        }
+        return result;
     }
 
     public static Boolean isIsogram(String str) {
-        return null;
+        char[] letters = str.toCharArray();
+        for(int i = 0;i < letters.length;i++){
+            for (int j = i+1; j < letters.length;j++){
+                if (letters[i] == letters[j]){
+                    return false;
+                }
+            }
+        }
+        return true;
     }
 
     public static Boolean hasDuplicateConsecutiveCharacters(String str) {
-        return null;
+        char[] letters = str.toCharArray();
+            for (int i = 0;i < letters.length-1;i++){
+                if (letters[i] == letters[i+1]){
+                    return true;
+                }
+            }
+        return false;
     }
 
     public static String removeConsecutiveDuplicateCharacters(String str) {
-        return null;
+        int dupeCounter = 0;
+        char[] letters = str.toCharArray();
+        String result = "";
+        for (int i = 0;i< letters.length-1;i++){
+            int j = i+1;
+            dupeCounter = 0;
+            while (letters[i]==letters[j] && j < letters.length) {
+                dupeCounter++;
+                j++;
+            }
+            if (dupeCounter > 0){
+                for (int d = i; d <= i+dupeCounter; d++){
+                    letters[d] = '5';
+                }
+            }
+        }
+        for (char letter : letters){
+            if (letter!='5'){
+                result += letter;
+            }
+        }
+        return result;
     }
 
+    public static char caseChar(char chr){
+        if (Character.isLowerCase(chr)){
+            return String.valueOf(chr).toUpperCase().charAt(0);
+        } else {
+            return String.valueOf(chr).toLowerCase().charAt(0);
+        }
+
+    }
     public static String invertCasing(String str) {
-        return null;
+        char[] letters = str.toCharArray();
+        String result = "";
+        for(char letter : letters){
+            result += caseChar(letter);
+        }
+        return result;
     }
 }

src/main/java/rocks/zipcode/quiz4/objectorientation/account/Account.java

@@ -3,11 +3,17 @@
 /**
  * @author leon on 30/12/2018.
  */
-public class Account extends BankAccount {
+public class Account {
+    Long id;
+    double balance;
+
+
+
     public Long getId() {
-        return null;
+        return id;
     }
 
     public void setId(Long id) {
+        this.id = id;
     }
 }

src/main/java/rocks/zipcode/quiz4/objectorientation/account/Bank.java

@@ -1,17 +1,29 @@
 package rocks.zipcode.quiz4.objectorientation.account;
 
+import java.util.ArrayList;
+
 /**
  * @author leon on 27/12/2018.
  */
 public class Bank {
+    ArrayList<BankAccount> accountList;
+
+    public Bank(){
+        this.accountList = new ArrayList<BankAccount>();
+    }
+
     public BankAccount removeBankAccountByIndex(Integer indexNumber) {
-        return null;
+        BankAccount removed = accountList.get(indexNumber);
+        accountList.remove((int) indexNumber);
+        return removed;
     }
 
     public void addBankAccount(BankAccount bankAccount) {
+        accountList.add(bankAccount);
     }
 
     public Boolean containsBankAccount(BankAccount bankAccount) {
-        throw new UnsupportedOperationException("Method not yet implemented");
+        return accountList.contains(bankAccount);
+
     }
-}
+}