Need to find Basic Operations Sets Union/Intersect/Symmetric Difference JAVA

Question

Need to finish implementing this to use UseSet class. Not sure if what I have implemented is 100% correct.

However I need help with the Union and SysDiff.

public class Set
{
   private ArrayList<Integer> elements;

   public Set()
   {
       elements = null;
   }

   public Set(ArrayList<Integer> s)
   {
       int i;
       elements = new ArrayList<Integer>();
       for(i=0; i<s.size(); i++)
          elements.add(s.get(i));
   }

   public Set(int[] s)
   {
       int i;
       elements = new ArrayList<Integer>();
       for(i=0; i<s.length; i++)
          elements.add(s[i]);
   }

   public String toString()
   {
       //implement this method
   }

   public boolean isElement(int elt)
   {
       int i
    for (i=0; i < elements.size(); i++)
    {
        if (elements.get(i) == elt)
        return true;
    }
    return false

   }

   public int cardinality()
   {
       return elements.size();
   }

   public Set intersect(Set s)
   {
    Array list <interger> iset = new Array(ist<interger>();
    int i;
    for (i=0; i<elements.size(); i++)
    {
        if (s2.isElement (elements.get(i)))
        iSet.add(elements.get(i)));
   }
    return new set(iset)
}

   public Set union(Set s)
   {
       //implement this method
   }

   public Set symDiff(Set s)
   {
       //implement this method
   }

Answer 1

Have you considered using one of the Java-provided classes, such as TreeSet ? Most of the basic set operations can be implemented far more easily using such a class as a starting point.

For example:

• Your isElement() method is named contains() in Set / TreeSet

• cardinality() is size()

• intersect can be implemented using retainAll()

• union() can be implemented using addAll()

• symDiff() can be implemented using removeAll() to remove the intersection elements from the union of two sets.

Answer 2

Please see the Oracle documentation on performing mathematical set operations with the java Set interface:

http://download.oracle.com/javase/tutorial/collections/interfaces/set.html

You can do unions and intersects with ease.

Answer 3

Java has its basic implementation. For more capabilities, try the Apache Commons library:

Commons-Collections seek to build upon the JDK classes by providing new interfaces, implementations and utilities. There are many features, including...

http://commons.apache.org/collections/

The CollectionUtils class is particularly useful for your task (eg, addAll:

http://commons.apache.org/collections/api-release/org/apache/commons/collections/CollectionUtils.html#addAll(java.util.Collection,%20java.util.Enumeration ).

You can see the implementation and take ideas here:

http://svn.apache.org/viewvc/commons/proper/collections/trunk/src/java/org/apache/commons/collections/CollectionUtils.java?view=markup