src/main/java/rocks/zipcode/quiz5/arrays/ArrayUtils.java

 package rocks.zipcode.quiz5.arrays;
 
+import java.util.ArrayList;
+import java.util.List;
+
 /**
  * @author leon on 01/01/2019.
  */
 public class ArrayUtils {
     public static String getMiddleElement(String[] values) {
-        return null;
+
+        String result ="";
+
+        for( int i =0; i<= values.length-1; i++) {
+            if (values[i] == values[values.length / 2])
+                result = values[i];
+        }
+        return result;
+
     }
 
     public static String[] removeMiddleElement(String[] values) {
-        return null;
+        List<String> list = new ArrayList<>();
+        String[] finalArray = new String[values.length -1];
+
+
+        for( int i =0; i< values.length; i++)
+            if(values[i]!=values[values.length/2])
+                list.add(values[i]);
+
+        return list.toArray(finalArray);
     }
 
     public static String getLastElement(String[] values) {
-        return null;
+        String result="";
+       result = values[values.length-1];
+       return result;
     }
 
     public static String[] removeLastElement(String[] values) {
-        return null;
+
+        String[] finalArray = new String[values.length-1];
+
+        for(int i=0; i< finalArray.length; i++) {
+            finalArray[i] = values[i];
+        }
+        return finalArray;
+
     }
 }

src/main/java/rocks/zipcode/quiz5/collections/Bank.java

 
 import rocks.zipcode.quiz5.objectorientation.account.BankAccount;
 
+import java.util.ArrayList;
+import java.util.List;
+
 /**
  * @author leon on 27/12/2018.
  */
 public class Bank {
     public BankAccount removeBankAccountByIndex(Integer indexNumber) {
-        return null;
+        List<BankAccount> list = new ArrayList<>();
+        BankAccount newType = new BankAccount();
+return null;
+
     }
 
     public void addBankAccount(BankAccount bankAccount) {

src/main/java/rocks/zipcode/quiz5/fundamentals/Calculator.java

  */
 public class Calculator {
     public static Double squareRoot(Double value) {
-        return null;
+
+        return Math.sqrt(value);
     }
 
     public static Double square(Double value) {
-        return null;
+        Double result = value*value;
+
+
+        return result;
     }
 
     public static Double[] squareRoots(Double... value) {
-        return null;
+        Double[] newArray = new Double[value.length];
+
+        for(int i =0; i<newArray.length; i++){
+            newArray[i] = squareRoot((value[i]));
+        }
+
+        return newArray;
     }
 
     public static Double[] squares(Double... values) {
-        return null;
+        Double[] finalArray = new Double[values.length];
+        for(int i=0; i< finalArray.length; i++){
+            finalArray[i] = square(values[i]);
+        }
+        return finalArray;
     }
 
     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;
     }
 }