The role of private in java

The private keyword in Java limits the access scope of members and only allows access within the class in which they are declared, thereby achieving data hiding, encapsulation, security, and on-demand visibility. Access restrictions include: subclasses, other classes in the same package, other modules, and reflection (requires additional permissions). Exceptions include: friend classes and careful use of reflection.

The role of private keyword in Java

In Java, the private keyword is used to restrict variables and methods or class access scope. It is the most restrictive access control, allowing access only within the class in which the member is declared.

Function:

• Data hiding: private members can only be accessed within the class, thus hiding implementation details and preventing external code modification or misuse these members.
• Encapsulation: private members separate the internal state of the class from the external interface, improving the maintainability and reusability of the code.
• Security: Restrict external access to critical data and enhance application security.
• On-demand visibility: Expose private members only when needed, reducing code complexity and increasing efficiency.

Usage:

The private keyword is placed before the variable, method or class declaration. For example:

private int age; // 私有变量
private void calculate() {} // 私有方法
class PrivateClass {} // 私有内部类

Access restrictions:

private members cannot be accessed in the following situations:

• Subclass
• Other classes in the same package
• Other modules in the application
• Reflection (requires additional permissions)

Exceptions:

• Friend class: By declaring a friend class, you can access the private members of other classes.
• Reflection: Using the Java Reflection API, private members can be accessed and modified. However, this requires system permissions and should be used with caution.

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