Sugar4j Tutorial

Hello World

We will create a Sugar4j class that outputs the Hello World program:

package tutorial;

import sugar4j.Sugar4j;

public class HelloWorldSugar extends Sugar4j<HelloWorldSugar> {

  public HelloWorldSugar() {
    super("tutorial.HelloWorld");
  }

  public void doCreate() {

    beginCompilationUnit();

    publicc().classs().begin();
    {
      mainn().begin();
      {
        call(Systemout, "println", quote("Hello world!")).eos();
      }
      end();
    }
    end();
  }

  public static void main(String[] args) {
    java.lang.System.out.println(new HelloWorldSugar().create());
  }
}

Running the program prints out the expected result:

package tutorial;
public class HelloWorld {
  public static void main(String[] args) {
    System.out.println("Hello world!");
  }
}

1	For every class/code to generate, you'll create a subclass of Sugar4j. The type parameter is the subclass itself. As a suggestion, the sugar class is named by appending the "Sugar" suffix to the name of the class that the sugar generates.
2	Calls the super constructor with the full qualified class name that this sugar class creates.
3	Implement the `doCreate()` method. The content of this method forms the 'compilation unit' or simply the Java file that is to be generated.
4	`beginCompilationUnit()` outputs the file header and the package declaration. This is most likely the first call you'll made within the `doCreate()` method.
5	The class declaration. `publicc()` outputs the `public` modifier, `classs()` outputs the `class` keyword followed by the simple name of the sugar's class; it's the shorthand for `classs(getClassSimpleName())`. The `begin()` and `end()` methods outputs the beginning and ending of a block (`{ }`). We strongly encourage you to use nested blocks within the `begin()` and `end()` calls to improve readability of the structure of the sugar class.
6	`mainn()` declares the well known `main(String[])` method.
7	Calls the method `println` on the object `Systemout` with the parameter `quote("Hello world!")`. `Systemout` is the string constant `"System.out"`, declared in the `sugar4j.lang.JavaLang` interface, which is implemented by Sugar4j. `quote()` instructs to output a string literal. `eos()` - EndOfStatement - instructs to output a semicolon.
8	Creates a new `HelloWorldSugar` instance, calls `create()` to generated it's content and prints out the content. The Sugar4j's `toString()` method is overridden so that it returns the content generated so far. Note the full qualified name to address `java.lang.System`. This is necessary because Sugar4j declares a `System` string constant which shadows the `java.lang.System` identifier.

As you can see, Java code that is to be generated (the template code) resides in the same class as your dynamic code. There is no need for external template files like .jsp/.php/.jet and the like.