Java: How to validate email inside a java Person class

Question

I am new to Java, and I have built a Person class (Code below) with the email as a username. Now, I want to validate or verify that the username used is an email address. How do I validate within the class itself? I am looking for the simplest way possible.

public class Person {
    private String email;
    private String password;

    public Customer(String username, String password) {
        this.email = email;
        this.password = password;
    }

    public void setUsername(String email){
        this.email = email;
    }

    public void setPassword(String password){
        this.password = password;
    }