what is java field

What is the difference between properties and fields in Java?

Properties in Java can usually be understood as get and set methods.

The field (field) is usually called "class member" or "class member variable", sometimes also called "domain", which is understood as "data member" and is used to carry data.

Field (field)

Class member (field), usually a class member variable defined in the class ,

For example:

public class A{
    private String s = "123";
}

We can say that there is a member variable in class A called s, and class A has a field s.

Fields are generally used to carry data, so for the sake of security, they are generally defined as private.

Fields and constants describe the data (domain) of the class. When some parts of these data are not allowed to be accessed by the outside world,

According to the principle of "object encapsulation", we should try to avoid encapsulating a Fields of a type are made public to the outside world. Except final modified constants.

Generally set it to private type. Since it is private, how can the outside world access it? Of course, it is through Java's attribute method!

Attributes (property)

Attributes are limited to the declaration of methods in the class and are not related to other members of the class and belong to the category of JavaBean.

For example:

void setA(String s){}
String getA(){}

When a class has such a pair of methods, we can say that this class has a readable and writable a property (note that Lowercase a). If the set method is removed, it is a readable attribute, and vice versa.

The rule is: remove the remaining string after get or set

Summary:

The purpose of distinguishing attributes and fields is for better To achieve data security, for example, when we want to assign a value to an attribute of a class or use it in other classes, we need to set this field to public. However, this allows arbitrary read and write operations on the field, which is very detrimental to data security. So attributes were added. Simply put, attributes realize the encapsulation of fields. Attributes have get and set methods to control fields. The attributes of this field only have set methods and no get methods, so only assignment operations can be performed on this method, and there is no read operation. ,vice versa. That is, the operations on fields are controlled through attributes.

You can create attributes and encapsulate fields and attributes together. Through attributes, you can access data members just like fields, realize data encapsulation, avoid illegal data assignment, ensure data integrity, and avoid modification of the entire program when modifications occur within the class.

Reflection based on get and set methods will not destroy object data, and the IDE can make some intelligent prompts through conventions. If you use reflection yourself and you want to do some general processing to traverse each field, no one will tell you which field can be written and which can be read, so you can't handle it.

The above is the detailed content of what is java field. For more information, please follow other related articles on the PHP Chinese website!