Stream::anyMatch

Since Java 8 you could use Stream::anyMatch.

setA.stream().anyMatch(setB::contains)

Because an hashSet uses the hashcode value of the object to store it. So it requires that you have to override the method hashCode in your own class. Since you didn't override it, it uses the hashCode method inherited from the object class.

The hashcode from the object class is calculated with the memory address of your object, i.e :

UserDefinedName p = new UserDefinedName("Carballo", "Videl");
System.out.println(p);
System.out.println(0x1e5e2c3);
System.out.println(p.hashCode());

Output :

UserDefinedName@1e5e2c3
31843011
31843011

So if you tried this, you will see that it outputs true :

Set<UserDefinedName> s = new HashSet<UserDefinedName>();
UserDefinedName p = new UserDefinedName("Carballo", "Videl");
s.add(p);
System.out.println(s.contains(p));

Now if you want to compare your User class correclty, you will have to override your hashCode method (you can generated it with eclipse) to generate the hashCode your object field by field.

If you have this method to your class, this will print true for the code you provide.

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

Yes this is possible by overriding the equals() method.

@Override 
public boolean  equals (Object object) {
     
}

You just want to check everything works in the equals method.

Code:

package com.webapp.test;

import java.util.ArrayList;
import java.util.List;

public class EmployeeModel {    

    public EmployeeModel(String name, String designation, long age) {
        this.name = name;
        this.designation = designation;
        this.age = age;
    }

    private String name;
    private String designation;
    private long age;

    public String getName() {
        return name;
    }

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

    public String getDesignation() {
        return designation;
    }

    public void setDesignation(String designation) {
        this.designation = designation;
    }

    public long getAge() {
        return age;
    }

    public void setAge(long age) {
        this.age = age;
    }

    @Override
    public boolean equals (Object object) {
        boolean result = false;
        if (object == null || object.getClass() != getClass()) {
            result = false;
        } else {
            EmployeeModel employee = (EmployeeModel) object;
            if (this.name == employee.getName() && this.designation == employee.getDesignation() && this.age.equals(employee.getAge())) {
                result = true;
            }
        }
        return result;
    }
}

public static void main(String args[]) {
    EmployeeModel first = new EmployeeModel("Sameer", "Developer", 25);
    EmployeeModel second = new EmployeeModel("Jon", "Manager", 30);
    EmployeeModel third = new EmployeeModel("Priyanka", "Tester", 24);

    List<EmployeeModel> employeeList = new ArrayList<EmployeeModel>();
    employeeList.add(first);
    employeeList.add(second);
    employeeList.add(third);
    
    EmployeeModel checkUserOne = new EmployeeModel("Sameer", "Developer", 25);
    System.out.println("Check checkUserOne is in list or not ");
    System.out.println("Is checkUserOne Present = ? " + employeeList.contains(checkUserOne));
    
    EmployeeModel checkUserTwo = new EmployeeModel("Tim", "Tester", 24);
    System.out.println("Check checkUserTwo is in list or not");
    System.out.println("Is checkUserTwo Present = ? " + employeeList.contains(checkUserTwo));

}

Output:

Check checkUserOne is in list or not 
Is checkUserOne Present = ? true
Check checkUserTwo is in list or not 
Is checkUserTwo Present = ? false