SE450: Horstmann Chapter 1: "Hello, World" in Java

Construct new objects with new operator
```
new Greeter("World")
```
Can invoke method on newly constructed object
```
new Greeter("World").sayHello()
```
More common: store object reference in object variable
```
Greeter worldGreeter = new Greeter("World");
```
Then invoke method on variable:
```
String greeting = worldGreeter.sayHello();
```