MathUtilities.java

     * @return sum of `baseValue` and `difference`
     */
    public Integer add(int baseValue, int difference) {
-       return null;
+       return baseValue + difference;
    }
 
    /**
     * @return sum of `baseValue` and `difference`
     */
    public Long add(long baseValue, long difference) {
-       return null;
+       return baseValue + difference;
    }
 
    /**
     * @return sum of `baseValue` and `difference`
     */
    public Short add(short baseValue, short difference) {
-       return null;
+       //return baseValue + difference;
+       return (short) (baseValue + difference);
    }
 
    /**
     * @return sum of `baseValue` and `difference`
     */
    public Byte add(byte baseValue, byte difference) {
-       return null;
+       return (byte) (baseValue + difference);
+      
    }
 
    /**
     * @return sum of `baseValue` and `difference`
     */
    public Float add(float baseValue, float difference) {
-       return null;
+       return (float) (baseValue + difference);
    }
 
    /**
     * @return sum of `baseValue` and `difference`
     */
    public Double add(double baseValue, double difference) {
-       return null;
+       return (double) (baseValue + difference);
    }
 
    /**
     * @return difference between `baseValue` and `difference`
     */
    public Integer subtract(int baseValue, int difference) {
-       return null;
+       return baseValue - difference;
    }
 
    /**
     * @return difference between `baseValue` and `difference`
     */
    public Long subtract(long baseValue, long difference) {
-       return null;
+       return baseValue - difference;
    }
 
    /**
     * @return difference between `baseValue` and `difference`
     */
    public Short subtract(short baseValue, short difference) {
-       return null;
+       return (short)(baseValue - difference);
    }
 
    /**
     * @return difference between `baseValue` and `difference`
     */
    public Byte subtract(byte baseValue, byte difference) {
-       return null;
+       return (byte)(baseValue - difference);
    }
 
    /**
     * @return difference between `baseValue` and `difference`
     */
    public Float subtract(float baseValue, float difference) {
-       return null;
+       return (float)(baseValue - difference);
    }
 
    /**
     * @return difference between `baseValue` and `difference`
     */
    public Double subtract(double baseValue, double difference) {
-       return null;
+       return (double)(baseValue - difference);
    }
 
 
     * @return division of `dividend` by `divisor
     */
    public Integer divide(int dividend, int divisor) {
-       return null;
+       return dividend / divisor;
    }
 
    /**
     * @return division of `dividend` by `divisor
     */
    public Long divide(long dividend, long divisor) {
-       return null;
+       return dividend / divisor;
    }
 
    /**
     * @return division of `dividend` by `divisor
     */
    public Short divide(short dividend, short divisor) {
-       return null;
+       return (short)(dividend / divisor);
    }
 
    /**
     * @return division of `dividend` by `divisor
     */
    public Byte divide(byte dividend, byte divisor) {
-       return null;
+       return (byte)(dividend / divisor);
    }
 
    /**
     * @return division of `dividend` by `divisor
     */
    public Float divide(float dividend, float divisor) {
-       return null;
+       return (float)(dividend / divisor);
    }
 
    /**
     * @return division of `dividend` by `divisor
     */
    public Double divide(double dividend, double divisor) {
-       return null;
+       return (double)(dividend / divisor);
    }
 
 
     * @return product of `multiplicand` by `multiplier`
     */
    public Integer multiply(int multiplicand, int multiplier) {
-       return null;
+       return multiplicand * multiplier;
    }
 
    /**
     * @return product of `multiplicand` by `multiplier`
     */
    public Long multiply(long multiplicand, long multiplier) {
-       return null;
+       return multiplicand * multiplier;
    }
 
    /**
     * @return product of `multiplicand` by `multiplier`
     */
    public Short multiply(short multiplicand, short multiplier) {
-       return null;
+       return (short)(multiplicand * multiplier);
    }
    /**
     * @param multiplicand value to be multiplied
     * @return product of `multiplicand` by `multiplier`
     */
    public Byte multiply(byte multiplicand, byte multiplier) {
-       return null;
+       return (byte)(multiplicand * multiplier);
    }
 
    /**
     * @return product of `multiplicand` by `multiplier`
     */
    public Float multiply(float multiplicand, float multiplier) {
-       return null;
+       return (float)(multiplicand * multiplier);
    }
 
    /**
     * @return product of `multiplicand` by `multiplier`
     */
    public Double multiply(double multiplicand, double multiplier) {
-       return null;
+       return (double)(multiplicand * multiplier);
    }
 
 
      * @return true
     */
    public Boolean returnTrue() {
-       return null;
+       return true;
    }
 
    /**
     * @return false
     */
    public Boolean returnFalse() {
-       return null;
+       return false;
    }
 
 }

PredicateUtilities.java

     * @return true if `x` is greater than `y`
     */
    public Boolean isGreaterThan(int x, int y) {
-       return null;
+       if (x > y) {
+       return true;
+       } else {
+           return false;
+        }
    }
 
    /**
     * @return true if `x` is less than `y`
     */
    public Boolean isLessThan(int x, int y) {
-       return null;
+       if (x < y) {
+       return true;
+       } else {
+           return false;
+        }
    }
 
    /**
     * @return true if `x` is greater than or equal to `y`
     */
    public Boolean isGreaterThanOrEqualTo(int x, int y) {
-       return null;
+       if (x >= y) {
+       return true;
+       } else {
+           return false;
+        }
    }
 
    /**
     * @return true if `x` is less than or equal to `y`
     */
    public Boolean isLessThanOrEqualTo(int x, int y) {
-       return null;
+       if (x <= y) {
+       return true;
+       } else {
+           return false;
+        }
    }
 }

StringUtilities.java

      * @return `Hello World` as a string
      */
     public String getHelloWorld() {
-        return null;
+        return "Hello World";
     }
 
     /**
      * @return the concatenation of two strings, `firstSegment`, and `secondSegment`
      */
     public String concatenation(String firstSegment, String secondSegment){
-        return null;
+        return firstSegment + secondSegment;
     }
 
     /**
      * @return the concatenation of an integer, `firstSegment`, and a String, `secondSegment`
      */
     public String concatenation(int firstSegment, String secondSegment){
-        return null;
+        return firstSegment + secondSegment;
     }
 
     /**
      * @return the first 3 characters of `input`
      */
     public String getPrefix(String input){
-        return null;
+        return input.substring(0, 3);
+     
+  
     }
 
     /**
      * @return the last 3 characters of `input`
      */
     public String getSuffix(String input){
-        return null;
+        return input.substring(input.length()-3);
     }
 
     /**
      * @return the equivalence of two strings, `inputValue` and `comparableValue`
      */
     public Boolean compareTwoStrings(String inputValue, String comparableValue){
-        return null;
+        if (inputValue.equals(comparableValue)){    
+        return true;
+        } else {
+            return false;
+        }
     }
 
     /**
      * @return the middle character of `inputValue`
      */
     public Character getMiddleCharacter(String inputValue){
-        return null;
-    }
+        return inputValue.charAt((inputValue.length() - 1) / 2);
+}
 
     /**
      * @param spaceDelimitedString a string, representative of a sentence, containing spaces
      * @return the first sequence of characters
      */
     public String getFirstWord(String spaceDelimitedString){
-        return null;
+        return spaceDelimitedString.split(" ")[0];
     }
 
     /**
      * @return the second word of a string delimited by spaces.
      */
     public String getSecondWord(String spaceDelimitedString){
-        return null;
+        return spaceDelimitedString.split(" ")[1];
     }
 
     /**
      * @return an identical string with characters in reverse order.
      */
     public String reverse(String stringToReverse){
-        return null;
+        StringBuilder builder = new StringBuilder(stringToReverse);
+        return builder.reverse().toString();
     }
 
     /**
      * @return an identical string with spaces removed.
      */
     public String removeWhitespace(String input){
-        return null;
+        return input.replaceAll("\\s+", "");
     }
 
     /**
      * @return an identical string with spaces in the front and end removed.
      */
     public String trim(String input){
-        return null;
+        return input.trim();
     }
 }