what is a package in java

In order to better organize classes, Java provides a package mechanism to distinguish the namespace of class names.

##The role of package             (Recommended learning: java course   )

1 , Organize classes or interfaces with similar or related functions into the same package to facilitate the search and use of classes.

2. Like folders, packages also use a tree directory storage method. The names of classes in the same package are different, and the names of classes in different packages can be the same. When classes with the same class name in two different packages are called at the same time, the package name should be added to distinguish them. Therefore, packages can avoid name conflicts.

3. Packages also limit access permissions. Only classes with package access permissions can access classes in a certain package.

Java uses the package mechanism to prevent naming conflicts, access control, provide search and location of classes, interfaces, enumerations and annotations, etc.

The syntax format of the package statement is:

package pkg1[．pkg2[．pkg3…]];

For example, a Something.java file has its content

package net.java.util;
public class Something{
   ...
}

then its path It should be saved like net/java/util/Something.java. The function of package is to classify and save different Java programs so that they can be called by other Java programs more conveniently.

A package can be defined as a set of interconnected types (classes, interfaces, enumerations and annotations), providing access protection and namespace management functions for these types.

The following are some packages in Java:

java.lang-打包基础的类
java.io-包含输入输出功能的函数

Developers can package a set of classes and interfaces by themselves and define their own packages. And it is worth advocating to do this in actual development. After you complete the implementation of the class yourself, grouping related classes can make it easier for other programmers to determine which classes, interfaces, enumerations, annotations, etc. are related. .

Because the package creates a new namespace (namespace), it will not cause naming conflicts with any names in other packages. Using the package mechanism makes it easier to implement access control and makes it easier to locate related classes.

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