Validate Email & Password with Regular Expression in Android

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:padding="16dp"
    tools:context="tech.codingpoint.textinputlayoutexample.MainActivity">

    <android.support.design.widget.TextInputLayout
        android:id="@+id/text_input_email"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        app:errorEnabled="true">

        <android.support.design.widget.TextInputEditText
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:hint="Email"
            android:inputType="textEmailAddress" />

    </android.support.design.widget.TextInputLayout>

    <android.support.design.widget.TextInputLayout
        android:id="@+id/text_input_username"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        app:counterEnabled="true"
        app:counterMaxLength="15"
        app:errorEnabled="true">

        <android.support.design.widget.TextInputEditText
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:hint="Username"
            android:inputType="text" />

    </android.support.design.widget.TextInputLayout>

    <android.support.design.widget.TextInputLayout
        android:id="@+id/text_input_password"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        app:errorEnabled="true"
        app:passwordToggleEnabled="true">

        <android.support.design.widget.TextInputEditText
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:hint="Password"
            android:inputType="textPassword" />

    </android.support.design.widget.TextInputLayout>

    <Button
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:onClick="confirmInput"
        android:text="Confirm" />

</LinearLayout>

package tech.codingpoint.textinputlayoutexample;

import android.support.design.widget.TextInputLayout;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Patterns;
import android.view.View;
import android.widget.Toast;

import java.util.regex.Pattern;

public class MainActivity extends AppCompatActivity {
    private static final Pattern PASSWORD_PATTERN =
            Pattern.compile("^" +
                    //"(?=.*[0-9])" +         //at least 1 digit
                    //"(?=.*[a-z])" +         //at least 1 lower case letter
                    //"(?=.*[A-Z])" +         //at least 1 upper case letter
                    "(?=.*[a-zA-Z])" +      //any letter
                    "(?=.*[@#$%^&+=])" +    //at least 1 special character
                    "(?=\\S+$)" +           //no white spaces
                    ".{4,}" +               //at least 4 characters
                    "$");

    private TextInputLayout textInputEmail;
    private TextInputLayout textInputUsername;
    private TextInputLayout textInputPassword;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        textInputEmail = findViewById(R.id.text_input_email);
        textInputUsername = findViewById(R.id.text_input_username);
        textInputPassword = findViewById(R.id.text_input_password);
    }

    private boolean validateEmail() {
        String emailInput = textInputEmail.getEditText().getText().toString().trim();

        if (emailInput.isEmpty()) {
            textInputEmail.setError("Field can't be empty");
            return false;
        } else if (!Patterns.EMAIL_ADDRESS.matcher(emailInput).matches()) {
            textInputEmail.setError("Please enter a valid email address");
            return false;
        } else {
            textInputEmail.setError(null);
            return true;
        }
    }

    private boolean validateUsername() {
        String usernameInput = textInputUsername.getEditText().getText().toString().trim();

        if (usernameInput.isEmpty()) {
            textInputUsername.setError("Field can't be empty");
            return false;
        } else if (usernameInput.length() > 15) {
            textInputUsername.setError("Username too long");
            return false;
        } else {
            textInputUsername.setError(null);
            return true;
        }
    }

    private boolean validatePassword() {
        String passwordInput = textInputPassword.getEditText().getText().toString().trim();

        if (passwordInput.isEmpty()) {
            textInputPassword.setError("Field can't be empty");
            return false;
        } else if (!PASSWORD_PATTERN.matcher(passwordInput).matches()) {
            textInputPassword.setError("Password too weak");
            return false;
        } else {
            textInputPassword.setError(null);
            return true;
        }
    }

    public void confirmInput(View v) {
        if (!validateEmail() | !validateUsername() | !validatePassword()) {
            return;
        }

        String input = "Email: " + textInputEmail.getEditText().getText().toString();
        input += "\n";
        input += "Username: " + textInputUsername.getEditText().getText().toString();
        input += "\n";
        input += "Password: " + textInputPassword.getEditText().getText().toString();

        Toast.makeText(this, input, Toast.LENGTH_SHORT).show();
    }
}