Json/Apex: Assigning values to nodes on the Json Array - json

Question

I have an apex code that defines the JSON structure. I would like to seek for advice on how I will be able to assign values to the string fields on the JSON using Apex. The JSON will have an array (PackageData) which contains the fields that should contain the values
Apex code:
public class Shipment{
public PackageData[] PackageData;
}
public class PackageData{
public Packaging Packaging;
public Dimensions Dimensions;
public PackageWeight PackageWeight;
}
public class Packaging{
public string Code;
}
public class Dimensions{
public UnitOfMeasurement UnitOfMeasurement;
public string Length;
public string Width;
public string Height;
}
public class UnitOfMeasurement{
public string Code;
}
public class PackageWeight{
public UOM UOM;
public string Weight;
}
public class UOM{
public string Code;
}
JSON:
{
"PackageData": [
{
"Packaging": {
"Code": ""
},
"Dimensions": {
"UnitOfMeasurement": {
"Code": ""
},
"Length": "",
"Width": "",
"Height": ""
},
"PackageWeight": {
"UOM": {
"Code": ""
},
"Weight": ""
}
}
]
}

Answer 1

JSON are always string, so there are a parser which parse object to JSON String and vice versa
Parser does it's job and automatically parse to String, You need not worry for that
Json to Object:
ClassName objName = (ClassName) System.JSON.deserialize(jsonString, ClassName.class);
Object to Json:
String jsonString = System.JSON.serialize(objName);