如果仅在对象初始化期间给定内存，如何初始化类成员变量（实例变量）？

Question

As we know that a class can have objects which get memory only by new classname(). Then how it is possible to assign some value to an instance of a class.

class Work{
   public int a = 55;
}

class DoStuff{
      public static void main(String[] args){
      Work obj = new Work(); // intialises variable now
      System.out.println(obj.a) // a already has value 55
   }
}

Answer 1

Order of execution of Initialization blocks and constructor in Java

• Static initialization blocks will run whenever the class is loaded first time in JVM
• Initialization blocks run in the same order in which they appear in the program.
• Instance Initialization blocks are executed whenever the class is initialized and before constructors are invoked. They are typically placed above the constructors within braces.

https://www.geeksforgeeks.org/order-execution-initialization-blocks-constructors-java/

So in your case public int a = 55; is invoked before constructor of Work class. JVM first reserves memory for an object and then starts initialization of all object properties.