Ch54

 import java.util.*;
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 /**
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    TODO Write a one-sentence summary of your class here.
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    TODO Follow it with additional details about its purpose, what abstraction
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    it represents, and how to use it.
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    @author  TODO Your Name
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    @version TODO date
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    @author  Period - TODO Your Period
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    @author  Assignment - Ch54 IntegerSet
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    @author  Sources - TODO list collaborators
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  */
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 public class IntegerSet { 
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     private ArrayList<Integer> set;
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     /* construct a new empty IntegerSet object */
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     public IntegerSet() {
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         set = new ArrayList<Integer>();
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     }
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     /* utility method: return size of set */
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     public int size() {
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         return set.size();
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     }
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     /* 
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     * @param True if k is in the set
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     */
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     public boolean contains(int k) {
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         int count = 0;
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         for(int i=0; i<set.size();i++)
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         {
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             if (set.get(i) == k)
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             {
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                 count++;
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             }
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         }
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         if (count == 0)
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         {
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             return false;
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         }

 	 	
  (i.e. return x < 5;). If you are returning false when the if statments condition is true and returning true in the else branch, you can just return the NOT (!) of the condition instead (i.e. return !okay;).

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         return true;
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     }
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     /** 
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      * add the num into the set but only if it is not already in the set
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      * @return True if number was added to the set; False if it did not need to be added
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     */ 
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     public boolean add(int num) {
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         if (set.contains(num)){
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             return false;
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         } else {
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             set.add(num);
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             return true;
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         }
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     }
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     /* add elements from Array nums to set
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     * @param nums array of integers to add to the list
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     * @return count of elements successfully added
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     * postcondition: set has no duplicates (do not add duplicates)
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     */
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     public int addFromArray(int [] nums) {
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         int num = 0;
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         for(int n: nums){
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             if(add(n)){
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                 num++;
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             }
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         }
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         return num;
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     }
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     /**
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      * @param return a string that looks like {1 2 3}
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      * don't worry about the spaces as long as there is a space between the numbers
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      * there can be extra spaces before or after the { }
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      */
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     public String toString() {
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         String s = "{";
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         // TODO - concatenate all the number of the set into the string s
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         for (Integer i: set){
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             s = s + i + " ";
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         }
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         s = s + "}";
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         return s;
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     }
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     public static void main (String[] args) {
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         IntegerSet s = new IntegerSet();
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         System.out.println("Initial size is " + s.size());
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         System.out.println("Found a 6 in the list: " + s.contains(6));
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         s.add(2);
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         s.add(6);
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         s.add(8);
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         s.add(2);
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         s.add(6);
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         s.add(0);
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         System.out.println(s);
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         System.out.println("Size is now: " + s.size());         // should be 4
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         System.out.println("Adding another 0: " + s.add(0));
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         System.out.println("Adding a 10: " + s.add(10));
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         System.out.println("Size is now: " + s.size());         // should be 5
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         s = new IntegerSet();
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         int[] n = {2, 6, 8, 2, 6, 0};
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         int numAdded = s.addFromArray(n);
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         System.out.println("Size of new set from addFromArray: " + numAdded);   // should be 4
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         System.out.println(s);
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     }
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 }