Sample Code:

String tempStr = 'test.78@gmail.com';

if ( Pattern.matches( '[a-zA-Z0-9._-]+@[a-zA-Z]+.[a-zA-Z]{2,4}', tempStr ) ) {                         
    
    System.debug( 'Regex Matched' );
    
} else {                         
    
    System.debug( 'Regex Pattern not Matched' );
    
}

Output: