Example2.java

public class Bar extends Foo {
    
    private final String lastName;
    
    public Bar(String firstName, String lastName) {
        super(firstName);
        this.lastName = lastName;
    }
    
    public String getLastName() {
        return lastName;
    }
    
    @Override
    public boolean equals(Object obj) {
        if (this == obj) {
            return true;
        } 
        else if (!(obj instanceof Bar)) {
            return false;
        } 
        else {
            Bar bar = (Bar) obj;
            return Objects.equals(bar.getFirstName(), getFirstName()) 
                && Objects.equals(bar.lastName, lastName);
        }
    }
    
    public int hashCode() { /* ... */ }
}

Foo foo = new Foo("John");
Bar bar = new Bar("John", "Doe");
System.out.println(foo.equals(bar)); // true
System.out.println(bar.equals(foo)); // false