C#、Unity 数据类型的默认值

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class Main : MonoBehaviour{
	private bool boolVal;
	private byte byteVal;
	private double doubleVal;
	private float floatVal;
	private int intVal;
	private long longVal;
	private short shortVal;
	private uint uintVal;
	private char charVal;
	private string stringVal;
	private Vector2 vector2Val;
	private Vector3 vector3Val;
	private Man classVal;
	private CustomData structVal;

	private bool? boolVal2;
	private float? floatVal2;
	private int? intVal2;
	private System.Nullable<int> intVal3;
	private Vector2? vector2Val2;
	private Vector2? vector2Val3=null;
	private CustomData? structVal2=null;

	private void Start() {
		Debug.LogFormat("boolVal:{0}",boolVal);//output:boolVal:False
		Debug.LogFormat("byteVal:{0}",byteVal);//output:byteVal:0
		Debug.LogFormat("doubleVal:{0}",doubleVal);//output:doubleVal:0
		Debug.LogFormat("floatVal:{0}",floatVal);//output:floatVal:0
		Debug.LogFormat("intVal:{0}",intVal);//output:intVal:0
		Debug.LogFormat("longVal:{0}",longVal);//output:longVal:0
		Debug.LogFormat("{0}",shortVal);//output:shortVal:0
		Debug.LogFormat("uintVal:{0}",uintVal);//output:uintVal:0
		Debug.LogFormat("charVal:{0},{1}",charVal,charVal=='');//output:charVal:
		if(charVal=='')Debug.Log("True");//output:True
		Debug.LogFormat("vector2Val:{0},{1}",vector2Val,vector2Val==Vector2.zero);//output:vector2Val:(0.0, 0.0),True
		Debug.LogFormat("vector3Val:{0},{1}",vector3Val,vector3Val==Vector3.zero);//output:vector3Val:(0.0, 0.0, 0.0),True
		Debug.LogFormat("classVal:{0},{1}",classVal,classVal==null);//output:classVal:,True
		Debug.LogFormat("structVal:{0}",structVal);//output:structVal:CustomData

		Debug.LogFormat("boolVal2:{0}",boolVal2==null);//output:boolVal2:True
		Debug.LogFormat("floatVal2:{0}",floatVal2==null);//output:floatVal2:True
		Debug.LogFormat("intVal2:{0}",intVal2==null);//output:intVal2:True
		Debug.LogFormat("intVal3:{0}",intVal3==null);//output:intVal3:True
		Debug.LogFormat("vector2Val2:{0}",vector2Val2==null);//output:vector2Val2:True
		Debug.LogFormat("vector2Val3:{0}",vector2Val3==null);//output:vector2Val3:True
		Debug.LogFormat("structVal2:{0}",structVal2==null);//output:structVal2:True
	}
}

public class Man{
	
}
public struct CustomData{
	public int ID;
}