How to remove duplicate objects in a List<MyObject> without equals/hashcode?

Question

I have to remove duplicated objects in a List. It is a List from the object Blog that looks like this:

public class Blog {     private String title;     private String author;     private String url;     private String description;     ... } 

A duplicated object is an object that have title, author, url and description equal to other object.

And I can't alter the object. I can't put new methods on it.

How do I do this?

Answer 1

Here is the complete code which works for this scenario:

class Blog {     private String title;     private String author;     private String url;     private String description;       public String getTitle() {         return title;     }      public void setTitle(String title) {         this.title = title;     }      public String getAuthor() {         return author;     }      public void setAuthor(String author) {         this.author = author;     }      public String getUrl() {         return url;     }      public void setUrl(String url) {         this.url = url;     }      public String getDescription() {         return description;     }      public void setDescription(String description) {         this.description = description;     }      Blog(String title, String author, String url, String description)     {         this.title = title;         this.author = author;         this.url = url;         this.description = description;      }      @Override     public boolean equals(Object obj) {         // TODO Auto-generated method stub         if(obj instanceof Blog)         {             Blog temp = (Blog) obj;             if(this.title.equals(temp.title) && this.author.equals(temp.author) && this.url.equals(temp.url) && this.description.equals(temp.description))                 return true;         }         return false;     }      @Override     public int hashCode() {         // TODO Auto-generated method stub                  return (this.title.hashCode() + this.author.hashCode() + this.url.hashCode() + this.description.hashCode());             } } 

Here is the main function which will eliminate the duplicates:

public static void main(String[] args) {     Blog b1 = new Blog("A", "sam", "a", "desc");     Blog b2 = new Blog("B", "ram", "b", "desc");     Blog b3 = new Blog("C", "cam", "c", "desc");     Blog b4 = new Blog("A", "sam", "a", "desc");     Blog b5 = new Blog("D", "dam", "d", "desc");     List<Blog> list = new ArrayList();     list.add(b1);     list.add(b2);     list.add(b3);     list.add(b4);            list.add(b5);          //Removing Duplicates;     Set<Blog> s= new HashSet<Blog>();     s.addAll(list);              list = new ArrayList<Blog>();     list.addAll(s);             //Now the List has only the identical Elements }