java what is instantiation

The process of creating an object is called instantiation, so sometimes we also call the object an instance of a class.

Demo demo = new Demo();

The action of this statement is usually called creating an object, that is, instantiation. In fact, it contains four actions.

(1) The "new Demo" on the right uses the Demo class as a template to create a Demo class object (also referred to as the Demo object) in the heap space.

The () at the end of (2) means that after the object is created, the constructor of the Demo class is called immediately to initialize the newly generated object. There is definitely a constructor. If you don't write it, Java will add a default constructor for you.

(3) The "Demo demo" on the left creates a Demo class reference variable. The so-called Demo class reference is an object reference that can be used to point to the Demo object in the future.

(4) The "=" operator makes the object reference point to the Demo object just created.

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