In development, we must remember that there are classes first, and then objects.
Class: Represents a common product and is a comprehensive feature.
For example, a teacher is a class composed of teachers of various disciplines.
Object: A product of a personality, a characteristic of each. is a real existence.
For example, Xiao Ming is a real person.
A class consists of properties and methods.
Attribute: Equivalent to a characteristic.
Method: It is equivalent to a person's behavior: such as: eating, sleeping, talking, etc.
Definition Format of Classes and Objects
A class can be defined in JAVA using the following statement:
class class name{
property name;
return value type method name(){}
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Object definition:
In order for a class to really operate, it must rely on objects. The definition format of objects is as follows:
The first:
className objectName = new className();
The second:
declare object: class name object name = null;
instantiated object: object name = new class name();
Objects can be generated according to the above objects.
Call the property in the class:
object.property;
Call the method in the class:
object.method();
Example:
class Person{ //Define a class
//Define two properties in the class
String name;
int age;
public void tell(){ //Define a return value type and method name
System.out.println(name+age);
}
public class TestDemo{
public static void main(String[] args){
Person per =new Person(); //Define an object and declare and instantiate it
per.name = "Wang Er"; //object.attribute=content
per.age=20; //object.property=content
per.tell(); //call the method in the class through the object
}
}
}
If no property content is set, the default value appears.