How to do union, intersect, difference and reverse data in java

Question

I want to implement the union, intersect, difference and reverse operations in Java.

First I have 2 instances of ArrayList<Integer>

a = [0,2,4,5,6,8,10] b = [5,6,7,8,9,10] 

a union b should return c = [0,2,4,5,6,7,8,9,10]

a intersect b should return c = [5,8,10]

a difference b should return c = [0,2,4]

reverse a = [10,8,6,5,4,2,0]

Something like this.

How to implement that method in Java?

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Update: I have to start with this template:

package IntSet; import java.util.ArrayList; import java.util.Collection;   public class IntSet {  private ArrayList<Integer> intset;  public IntSet(){     intset = new ArrayList<Integer>(); }  public void insert(int x){     intset.add(x); }  public void remove(int x){     //implement here     intset.indexOf(x); }  public boolean member(int x){     //implement here     return true; }  public IntSet intersect(IntSet a){     //implement here     return a; }  public IntSet union(IntSet a){     //implement here     return a; }  public IntSet difference(IntSet a){     //implement here     IntSet b = new IntSet();     return b;  } 

Answer 1

First, the operations you describe (except reverse) are set operations, not list operations, so use HashSet or (if you need an ordering) TreeSet.

    Set<Integer> a = new TreeSet<Integer>(Arrays.asList(new Integer[]{0,2,4,5,6,8,10}));     Set<Integer> b = new TreeSet<Integer>(Arrays.asList(new Integer[]{5,6,7,8,9,10}));      //union     Set<Integer> c = new TreeSet<Integer>(a);     c.addAll(b);     System.out.println(c);      //intersection     Set<Integer> d = new TreeSet<Integer>(a);     d.retainAll(b);     System.out.println(d);      //difference     Set<Integer> e = new TreeSet<Integer>(a);     e.removeAll(b);     System.out.println(e);      //reverse     List<Integer> list = new ArrayList<Integer>(a);     java.util.Collections.reverse(list);     System.out.println(list);