Usage of field in java

Java fields are used to represent properties or status of a class and are accessed through the dot operator. A field's modifiers control its access level: public, protected, default, and private. Instance fields are associated with each instance, whereas static fields are associated with the class itself and are shared by all instances.

Usage of fields in Java

Fields in Java are used to represent attributes of classes or objects or status. It is a data member that stores data of a specific type.

Create fields

The field declaration syntax is as follows:

<修饰符> <数据类型> <字段名>;

Among them:

• Modifier: Control the access level of the field (public, protected, default, private)
• Data type : The data type that the field can store (int, double, String, etc.)
• Field name: The unique identifier of the field

Example:

public int age;
private String name;

Access field

Fields can be accessed through the dot operator:

// 获取对象的 age 字段
int age = object.age;

// 设置对象的 name 字段
object.name = "新的名字";

Field modifiers

The modifiers for fields in Java are as follows:

• public: Accessible throughout the program
• protected: Accessible in subclasses and the same package
• default (package access): only accessible within the same package
• private: only accessible within the class in which the field is defined

Instance fields and static fields

• Instance fields: Associated with instances of each class. Each instance of a class has its own copy of the instance fields.
• Static fields (also called class fields): associated with the class itself, rather than a specific instance. All instances of the same class share the same static fields.

Example:

// 实例字段
private int instanceNumber;

// 静态字段
public static int staticNumber;

Notes

• Fields are different from methods. Fields store data, while methods perform operations.
• The type of the field can be any Java data type (including custom types).
• The access level of a field is determined by its modifiers.
• Static fields can only be accessed by static methods.
• Fields can be initialized by the constructor.

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