What does inner mean in java

The inner modifier in Java is used to declare an inner class, a class nested in an outer class, which has the following advantages: encapsulates specific implementation details and improves code flexibility. Control access to external class members, enhancing security and modularity. Break code into smaller chunks to make maintenance and debugging easier.

inner in Java

inner is a modifier in Java, Used to declare an inner class. An inner class is a class that is nested within an outer class and has access to the outer class's private members.

Why use inner classes?

Inner classes are often used in the following scenarios:

• Create helpers or tools that are only used in external classes.
• Organize functionality into smaller chunks, thereby improving code readability and maintainability.
• Access private member variables or methods of external classes.

Creating an inner class

To create an inner class, use the inner modifier as follows:

public class OuterClass {
    private int x;

    public static void main(String[] args) {
        OuterClass outerClass = new OuterClass();
        OuterClass.InnerClass innerClass = outerClass.new InnerClass();
        innerClass.printX();
    }

    public class InnerClass {
        public void printX() {
            System.out.println(x);
        }
    }
}

Accessing external class members

Inner classes can access member variables and methods of external classes through the .this keyword, as shown below:

innerClass.printX(); // 调用 OuterClass 中的 printX() 方法

Type

Inner classes can be static or non-static:

• Static nested classes: Use static Keyword declaration, non-static members of external classes cannot be accessed.
• Non-static nested class: Not declared using the static keyword, all members of the outer class can be accessed.

Advantages

• Encapsulation: Internal classes can hide specific implementation details in external classes, improving the flexibility of the code functionality and reusability.
• Access control: Inner classes can control access to external class members to enhance security and modularity.
• Code Organization: Inner classes help break the code into smaller chunks, making maintenance and debugging easier.

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