Java Basic Concepts

Object: The function of the. is the specific entity that exists, with clearly defined characteristics and behavior.

Object-oriented: a way of knowing things, paying attention to the whole cognition of things, the most accord with the natural thinking habit of mankind.

A class is an abstraction of an object that is an instance of a class.

A class is a collection of sets of objects that have the same properties and behavior.

In software systems, we use classes to simulate real-life entities.

Attributes are used to describe the characteristics of an object, the properties of an object are independent from one another, and the properties of an object do not affect the changes of other object properties, which are also called member variables because they are part of an object.

Static variables are created outside the object and are variables shared by all objects, and static variables vary, affecting all objects.

Garbage collection mechanism: Reclaims objects that are not pointed to by the variable.

The difference between a base type and a reference type: 1. In the basic type variable, the specific data is stored. 2. In the reference type variable, the address of the object is stored.

There are three types of reference: class, Array, interface

Null indicates that no object address is stored in the variable, and a null pointer exception is thrown when a method and property call is made to a variable with a value of NULL

Java Basic Concepts