Declare in Groovy

In Groovy, we can declare a class using the class keyword followed by the class name. Here's an example:

class Person {
  String name
  int age
  
  void sayHello() {
    println "Hello, my name is ${name} and I am ${age} years old."
  }
}

In this example, we've declared a class called Person with two properties: name (of type String) and age (of type int). We've also defined a method called sayHello which simply prints a message with the name and age properties.

We can create an object of this class using the new keyword, like this:

def person = new Person(name: 'John', age: 30)

We can also access the properties and methods of the Person class using the dot notation, like this:

person.name = 'Jane'
person.sayHello()

This will update the name property of person to 'Jane' and call the sayHello method, which will print "Hello, my name is Jane and I am 30 years old."