confusion in java 8 method referencing for equals method implementation with BiPredicate

Question

I was practicing my Java 8 skills. I came across a strange (for me) code. I have my bean class Person with overridden equals method. Then I tried to implement BiPredicate with equals method. It ran successfully. Can anyone explains how's that possible..because in my opinion equals method takes 1 argument and BiPridicate's test method takes two arguments. How is it satisfying this condition?

My code--

Method_Ref1

package method_referencing;

import java.util.function.BiPredicate;
import method_referencing.Person;

//1. static ....
//2. instance ...
//3. arbitary object 
//4. constructor
public class Method_Ref1 {

    public static void main(String[] args) {

        System.out.println(checkHere(Person::equals));

    }

     static boolean checkHere(BiPredicate<Person,Person> pc) {
         Person p1 = new Person(11,"Tom","Male","coder");
         Person p2 =    new Person(21,"Tom","male","coder");
         return pc.test(p1, p2);
     }

}

Person

package method_referencing;

import java.io.Serializable;

public class Person implements Serializable{

    private static final long serialVersionUID = 5721690807993472050L;
    int id;
    String name;
    String gender;
    String note;

    public Person() {

    }

    public Person(int id, String name, String gender, String note) {
        this.id = id;
        this.name = name;
        this.gender = gender;
        this.note = note;
    }

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getGender() {
        return gender;
    }

    public void setGender(String gender) {
        this.gender = gender;
    }

    public String getNote() {
        return note;
    }

    public void setNote(String note) {
        this.note = note;
    }

    @Override
    public String toString() {
        return "id=" + id + ", name=" + name + ", gender=" + gender + ", note=" + note + "";
    }

    @Override
    public int hashCode() {
        final int prime = 31;
        int result = 1;
        result = prime * result + ((gender == null) ? 0 : gender.hashCode());
        result = prime * result + id;
        result = prime * result + ((name == null) ? 0 : name.hashCode());
        result = prime * result + ((note == null) ? 0 : note.hashCode());
        return result;
    }

    @Override
    public boolean equals(Object obj) {
        if (this == obj)
            return true;
        if (obj == null)
            return false;
        if (getClass() != obj.getClass())
            return false;
        Person other = (Person) obj;
        if (name == null) {
            if (other.name != null)
                return false;
        } else if (!name.equals(other.name))
            return false;
        return true;
    }

}

Answer 1

Object.equals() accepts a single parameter. It is right. But here your introduced a function that accepts both the object to compare (this) and the parameter expected for equals (the other object).
So you need a BiPredicate<Person,Person> to allow to pass both information.

I think that the origin of your confusion is the method reference :

checkHere(Person::equals); 

Convert it into a lambda, it should do things clearer : (o1, o2) -> o1.equals(o2)

You indeed need to pass two arguments to the function to allow it substitute o1 and o2 and you do that :

return pc.test(p1, p2);