Question

Write a method in the HashIntSet class called addAll that accepts another hash set as a parameter and adds all of the elements from the other set into the current set. For example, if the set stores [-5, 1, 2, 3] and the method is passed [2, 3, 6, 44, 79], your set would store [-5, 1, 2, 3, 6, 44, 79]. Write a method in the HashIntSet class called containsAll that accepts another hash set as a parameter and returns true if your set contains every element from the other set. For example, if the set stores [-2, 3, 5, 6, 8] and the method is passed [3, 6, 8], your method would return true. If the method were passed [3, 6, 7, 8], your method would return false because your set does not contain the value 7. Write a method in the HashIntSet class called equals that accepts another object as a parameter and returns true if the object is another HashIntSet that contains exactly the same elements. The internal hash table size and ordering of the elements does not matter, only the sets of elements themselves. Please also create a Main program to test the code. Provided Files ****************** HashIntSet.java ****************** // Implements a set of integers using a hash table. // The hash table uses separate chaining to resolve collisions. public class HashIntSet { private static final double MAX_LOAD_FACTOR = 0.75; private HashEntry[] elementData; private int size; // Constructs an empty set. public HashIntSet() { elementData = new HashEntry[10]; size = 0; } // Adds the given element to this set, if it was not already // contained in the set. public void add(int value) { if (!contains(value)) { if (loadFactor() >= MAX_LOAD_FACTOR) { rehash(); } // insert new value at front of list int bucket = hashFunction(value); elementData[bucket] = new HashEntry(value, elementData[bucket]); size++; } } // Removes all elements from the set. public void clear() { for (int i = 0; i < elementData.length; i++) { elementData[i] = null; } size = 0; } // Returns true if the given value is found in this set. public boolean contains(int value) { int bucket = hashFunction(value); HashEntry current = elementData[bucket]; while (current != null) { if (current.data == value) { return true; } current = current.next; } return false; } // Returns true if there are no elements in this queue. public boolean isEmpty() { return size == 0; } // Removes the given value if it is contained in the set. // If the set does not contain the value, has no effect. public void remove(int value) { int bucket = hashFunction(value); if (elementData[bucket] != null) { // check front of list if (elementData[bucket].data == value) { elementData[bucket] = elementData[bucket].next; size--; } else { // check rest of list HashEntry current = elementData[bucket]; while (current.next != null && current.next.data != value) { current = current.next; } // if the element is found, remove it if (current.next != null && current.next.data == value) { current.next = current.next.next; size--; } } } } // Returns the number of elements in the queue. public int size() { return size; } // Returns a string representation of this queue, such as "[10, 20, 30]"; // The elements are not guaranteed to be listed in sorted order. public String toString() { String result = "["; boolean first = true; if (!isEmpty()) { for (int i = 0; i < elementData.length; i++) { HashEntry current = elementData[i]; while (current != null) { if (!first) { result += ", "; } result += current.data; first = false; current = current.next; } } } return result + "]"; } // Returns the preferred hash bucket index for the given value. private int hashFunction(int value) { return Math.abs(value) % elementData.length; } private double loadFactor() { return (double) size / elementData.length; } // Resizes the hash table to twice its former size. private void rehash() { // replace element data array with a larger empty version HashEntry[] oldElementData = elementData; elementData = new HashEntry[2 * oldElementData.length]; size = 0; // re-add all of the old data into the new array for (int i = 0; i < oldElementData.length; i++) { HashEntry current = oldElementData[i]; while (current != null) { add(current.data); current = current.next; } } } // Represents a single value in a chain stored in one hash bucket. private class HashEntry { public int data; public HashEntry next; public HashEntry(int data) { this(data, null); } public HashEntry(int data, HashEntry next) { this.data = data; this.next = next; } } }

Answer 1

1. public void addAll(HashIntSet set) : This method accepts another hash set as a parameter and adds all of the elements from the this set into the current set.
   • Here we loop through all the elements inside the parameter set and get each HashEntry.
   • Using While Loop we loop to all HashEntry object inside given set
   • We check if its not null, then we add the data of this HashEntry in the current set object.
   • Then move to next HashEntry
   • Here we are using existing add(int value) function to add each data of given set to the existing set inside loop

   // Method accepts another hash set as a parameter and adds all of the elements from the this set into the current set.
   public void addAll(HashIntSet set)
   {
       for (int i = 0; i < set.elementData.length; i++)
       {
           HashEntry current = set.elementData[i];
           while (current != null)
           {
               this.add(current.data);
              
               current = current.next;
           }
       }
   }

========================================================================================

2. public boolean containsAll(HashIntSet set) : Method accepts another hash set as a parameter and returns true if your set contains every element from the other set.

• We check if the current is empty by calling isEmpty() method. If it returns true then we return false for contains all method.
• We loop through all the elements inside the parameter set and get each HashEntry.
• Using While Loop we loop to all HashEntry object inside given set
• We check if its not null, then we call contains(int value) methos to check if data of this HashEntry is present in the current set object.
• If any single data is not present in current object set then directly return false else set the result flag as true for each present value and return that result flag at the end.
• Then move to next HashEntry.

// Method accepts another hash set as a parameter and returns true if your set contains every element from the other set.
   public boolean containsAll(HashIntSet set)
   {
       boolean result = false;
       if (!isEmpty())
       {
           for (int i = 0; i < set.elementData.length; i++)
           {
               HashEntry current = set.elementData[i];
               while (current != null)
               {
                   if(this.contains(current.data))
                   {
                       result = true;
                   }
                   else
                   {
                       return false;
                   }
                   current = current.next;
               }
           }
       }
       return result;
   }

============================================================================================

3.    public boolean equals(HashIntSet set) : Method that accepts another object as a parameter and returns true if the object is another HashIntSet that contains exactly the same elements.

• We check if the size of given set and the current set is equal by calling existing size() function.
• If size is not equal then directly return false.
• If size if not equal then check if current set contains the entire given set by calling containsAll(HashIntSet set) created by us previously.
• Return the result returned by containsAll(..) method which will be true if all data is present else false.

   // Method that accepts another object as a parameter and returns true if the object is another HashIntSet that contains exactly the same elements.
   public boolean equals(HashIntSet set)
   {
       boolean result = false;
       if (this.size() == set.size())
       {
           result = this.containsAll(set);
       }
      
       return result;
   }

===========================================================================================

Please find the entire HashIntSet.java file below:-

//Implements a set of integers using a hash table.
// The hash table uses separate chaining to resolve collisions.
public class HashIntSet
{
   private static final double MAX_LOAD_FACTOR = 0.75;
   private HashEntry[] elementData;
   private int size;
  
   // Constructs an empty set.
   public HashIntSet()
   {
       elementData = new HashEntry[10]; size = 0;
   }
  
   // Adds the given element to this set, if it was not already
   // contained in the set.
   public void add(int value)
   { if (!contains(value))
       {
           if (loadFactor() >= MAX_LOAD_FACTOR)
           {
               rehash();
           }
           // insert new value at front of list
           int bucket = hashFunction(value);
           elementData[bucket] = new HashEntry(value, elementData[bucket]);
           size++;
       }
   }
  
   // Method accepts another hash set as a parameter and adds all of the elements from the this set into the current set.
   public void addAll(HashIntSet set)
   {
       for (int i = 0; i < set.elementData.length; i++)
       {
           HashEntry current = set.elementData[i];
           while (current != null)
           {
               this.add(current.data);
              
               current = current.next;
           }
       }
   }
  
   // Removes all elements from the set.
   public void clear()
   {
       for (int i = 0; i < elementData.length; i++)
       {
           elementData[i] = null;
       } size = 0;
   }
  
   // Returns true if the given value is found in this set.
   public boolean contains(int value)
   {
       int bucket = hashFunction(value);
       HashEntry current = elementData[bucket];
       while (current != null)
       {
           if (current.data == value)
           {
               return true;
           }
           current = current.next;
       } return false;
   }
  
   // Method accepts another hash set as a parameter and returns true if your set contains every element from the other set.
   public boolean containsAll(HashIntSet set)
   {
       boolean result = false;
       if (!isEmpty())
       {
           for (int i = 0; i < set.elementData.length; i++)
           {
               HashEntry current = set.elementData[i];
               while (current != null)
               {
                   if(this.contains(current.data))
                   {
                       result = true;
                   }
                   else
                   {
                       return false;
                   }
                   current = current.next;
               }
           }
       }
      
       return result;
   }
  
   // Method that accepts another object as a parameter and returns true if the object is another HashIntSet that contains exactly the same elements.
   public boolean equals(HashIntSet set)
   {
       boolean result = false;
       if (this.size() == set.size())
       {
           result = this.containsAll(set);
       }
      
       return result;
   }
  
   // Returns true if there are no elements in this queue.
   public boolean isEmpty()
   {
       return size == 0;
   }
  
   // Removes the given value if it is contained in the set.
   // If the set does not contain the value, has no effect.
   public void remove(int value)
   {
       int bucket = hashFunction(value);
       if (elementData[bucket] != null)
       {
           // check front of list
           if (elementData[bucket].data == value)
           {
               elementData[bucket] = elementData[bucket].next; size--;
           }
           }
           else
           {
               // check rest of list
               HashEntry current = elementData[bucket];
               while (current.next != null && current.next.data != value)
               {
                   current = current.next;
               }
               // if the element is found, remove it
               if (current.next != null && current.next.data == value)
               {
                   current.next = current.next.next; size--;
               }
           }
       }

   // Returns the number of elements in the queue.
   public int size()
   {
       return size;
   }
  
   // Returns a string representation of this queue, such as "[10, 20, 30]";
   // The elements are not guaranteed to be listed in sorted order.
   public String toString()
   {
       String result = "[";
       boolean first = true;
       if (!isEmpty())
       {
           for (int i = 0; i < elementData.length; i++)
           {
               HashEntry current = elementData[i];
               while (current != null)
               {
                   if (!first)
                   {
                       result += ", ";
                   }
                   result += current.data;
                   first = false;
                   current = current.next;
               }
           }
       }
      
       return result + "]";
   }
  
   // Returns the preferred hash bucket index for the given value.
   private int hashFunction(int value)
   {
       return Math.abs(value) % elementData.length;
   }
  
   private double loadFactor()
   {
       return (double) size / elementData.length;
   }
  
   // Resizes the hash table to twice its former size.
   private void rehash()
   {
       // replace element data array with a larger empty version
       HashEntry[] oldElementData = elementData;
       elementData = new HashEntry[2 * oldElementData.length]; size = 0;
       // re-add all of the old data into the new array
       for (int i = 0; i < oldElementData.length; i++)
       {
           HashEntry current = oldElementData[i];
           while (current != null)
           {
               add(current.data); current = current.next;
           }
       }
   }
  
   // Represents a single value in a chain stored in one hash bucket.
   private class HashEntry
   {
       public int data;
       public HashEntry next;
      
       public HashEntry(int data)
       {
           this(data, null);
       }
      
       public HashEntry(int data, HashEntry next)
       {
           this.data = data;
           this.next = next;
       }
   }
}

-----------------------------------------------------------------------------------------------------------------------------------

Main.java file to test the sets:-

public class Main
{
   public static void main(String[] args)
   {
       HashIntSet set1 = new HashIntSet();
       set1.add(1);
       set1.add(2);
       set1.add(2);
       set1.add(3);
       set1.add(3);
       set1.add(4);
       System.out.println("HashSet ==> "+set1.toString());

       HashIntSet set2 = new HashIntSet();
       set2.add(3);
       set2.add(4);
       set2.add(5);
       set2.add(5);
       System.out.println("set1 Contains set2 ? ==> "+set1.containsAll(set2));
      
       set1.addAll(set2);
      
       System.out.println("HashSet after addAll ==> "+set1.toString());
       System.out.println("set1 Contains set2 after addind set2 in set1 ==> "+set1.containsAll(set2));
       System.out.println("set1 Equals set1 ? ==> "+set1.equals(set1));
       System.out.println("set1 Equals set2 ? ==> "+set1.equals(set2));
   }
}

Please find the result of above testing below:-

eclipse-workspace - Test/src/test/Main.java - Eclipse Eile Edit Source Refactor Navigate Search Project Run Window Help & ION 3.0 200- HashIntSetjava Main.java X 50 public static void main(String[] args) HashIntset seti = new HashIntset(; seti.add(1); seti.add(2); seti.add(2); seti.add(3); seti.add(3); seti.add(4); System.out.println("HashSet ==> "+seti.tostring(); HashIntset set2 = new HashIntset(); set2.add(3); set2.add(4); set2.add(5); set2.add(5); System.out.println("seti contains set2 ? ==> "+seti.containsAll(set2)); seti.addAll(set2); System.out.println("HashSet after addAll ==> "+seti.tostring(); System.out.println("seti contains set2 after addind setz in seti ==> "+seti.containsAll(set2)); System.out.println("seti Equals seti ? ==> "+seti.equals(seti)); System.out.println("seti Equals set2 ? ==> "+seti.equals(set2)); @ Console X Tasks Debug <terminated> Main (1) [Java Application] C:\Program Files\AdoptOpen DK jre-8.0.202.08\bin\javaw.exe (Mar 9, 2020, 1:02:13 PM) HashSet ==> (1, 2, 3, 4] seti contains set2 ? ==> false HashSet after addAll ==> (1, 2, 3, 4, 5] seti contains set2 after addind set2 in seti ==> true seti Equals seti ? ==> true seti Equals set2 ? ==> false