如何在Java HashSet中删除重复项

Question

I have a set of this structure. How to remove duplicates of equal object of that class? Equals means field File plik is the same.

EDIT: But the problem gut bigger I don't have duplicates but I would like to replace old SET member by new.

Withoud 3rd party libraries.

import java.io.*;

public class WordInfo implements Serializable {
    File plik;
    Integer wystapienia;

    public WordInfo(File plik, Integer wystapienia) {
        this.plik = plik;
        this.wystapienia = wystapienia;
    }

    public String toString() {
    //  if (plik.getAbsolutePath().contains("src") && wystapienia != 0)
            return plik.getAbsolutePath() + "\tWYSTAPIEN " + wystapienia;
    //  return "";
    }

}

EDIT

I don't have this HashCodeBuilder I want to use Java standard libraries

 public int hashCode() {
            return new HashCodeBuilder(17, 31).append(plik).append(wystapienia).toHashCode();
        }

    public boolean equals(Object obj) {
        File f = (File) obj;
        return(plik.getAbsoluteFile().equals(f.getAbsolutePath()));
    }

Answer 1

As discussed here , override equals.

public class Person {
    private String name;
    private int age;
    // ...

    public int hashCode() {
        return new HashCodeBuilder(17, 31). // two randomly chosen prime numbers
            // if deriving: appendSuper(super.hashCode()).
            append(name).
            append(age).
            toHashCode();
    }

    public boolean equals(Object obj) {
        if (obj == null)
            return false;
        if (obj == this)
            return true;
        if (obj.getClass() != getClass())
            return false;

        Person rhs = (Person) obj;
        return new EqualsBuilder().
            // if deriving: appendSuper(super.equals(obj)).
            append(name, rhs.name).
            append(age, rhs.age).
            isEquals();
    }
}

Answer 2

public class WordInfo implements Serializable {
    File plik;

Considering that following is how you can override the equals and hashCode method as per your requirement:

@Override
public boolean equals(Object obj) {
    if(this == obj) return true;
    if(!(obj instanceof WordInfo)) return false;
    return this.plik.equals(((WordInfo) obj).plik);
}

@Override
public int hashCode() {        
    return this.plik.hashCode();
}