How to remove duplicate objects in a List 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;
    priv         


        

Answer 1

It is recommended to override equals() and hashCode() to work with hash-based collections, including HashMap, HashSet, and Hashtable, So doing this you can easily remove duplicates by initiating HashSet object with Blog list.

List blogList = getBlogList();
Set noDuplication = new HashSet(blogList);

But Thanks to Java 8 which have very cleaner version to do this as you mentioned you can not change code to add equals() and hashCode()

Collection uniqueBlogs = getUniqueBlogList(blogList);

private Collection getUniqueBlogList(List blogList) {
    return blogList.stream()
            .collect(Collectors.toMap(createUniqueKey(), Function.identity(), (blog1, blog2) -> blog1))
            .values();
}
List updatedBlogList = new ArrayList<>(uniqueBlogs);

Third parameter of Collectors.toMap() is merge Function (functional interface) used to resolve collisions between values associated with the same key.