builder.beginClass(new ClassDef());
builder.addField(new FieldDef());// f0
builder.addJavaDoc("Hello");
builder.addMethod(new MethodDef());//m0
builder.addJavaDoc("Hello field");
builder.addField(new FieldDef());//f1
builder.addMethod(new MethodDef());//m1
builder.addJavaDoc("World");
builder.addMethod(new MethodDef());//m2
builder.endClass();
JavaSource source = builder.getSource();