What is the usage of private in Java?

In Java, private is an access modifier used to restrict access to a class’s member variables and methods.

When a member variable or method is declared as private, it can only be accessed within the same class and cannot be directly accessed in other classes. This means that private members can only be accessed through the class’s public interface (i.e. public methods).

The main purpose of private members is to conceal the internal implementation details of a class while providing a secure public interface. This ensures that the internal implementation details of the class are not accessed or modified by external classes, thereby enhancing encapsulation and data security.

Here are some common uses of “private”:

1. Private member variables can be indirectly accessed and modified by providing public getter and setter methods, allowing for control over access and modification logic for the member variables.

private int age;

public int getAge() {
    return age;
}

public void setAge(int age) {
    this.age = age;
}

1. Private member methods can only be called within the class itself and cannot be accessed from outside. This can be used to implement auxiliary functions or internal logic within the class.

private void helperMethod() {
    // do something
}

public void publicMethod() {
    // call private helper method
    helperMethod();
}

In conclusion, the main purpose of the private keyword is to control access, ensure that internal details of a class are not directly accessed or modified by external classes, and provide a public interface to operate on private members. This helps achieve encapsulation, security, and maintainability of the code.