Question

Class Order
{
  String  name;
  Order(String n)
   { name = n; }

 //setter and getters of name
}

Order a = new Order("same");
Order b = new Order("same");
Order c = new Order("diff");

List<Order> nameList// a,b,c

I want to

seperate list of Orders 
     List<Order> dupList// a,b
     List<Order> nondupList// c

Now I want to check whether same name is available in multiple orders of “nameList”.

I achieved that using index of List and compare with other than that index List Orders.

But is there any other better way to achieve this.

Answer 1

Probably one other way could be – Override hashCode method and equals method. Generate hasCode on calculation of string name.

public class Order {
    String name;

    public Order(String n) {
        name = n;
    }

    // setter and getters of name
    @Override
    public int hashCode() {
        int h = 0;
        int len = name.length();
        for (int i = 0; i < len; i++)
            h = 31 * h + name.charAt(i);
        return h;
    }
    @Override
    public boolean equals(Object obj) {
        if(obj == null)
            return false;
        else if(this.hashCode() == obj.hashCode())
            return true;
        return false;
    }
}

…

List<Order> nameList = ...;// a,b,c
Set<Order> nonDuplicate= new HashSet<Order>(nameList);