Local Inner Class in Java

A Local Inner Class in Java is a class defined inside a method, a constructor, or a block and is used only within that limited scope. It improves encapsulation and helps keep logic close to where it is used.

Declared inside a method, constructor, or block; scope is limited to that block
Can access outer class members and final / effectively final local variables
Cannot use access modifiers (public, private, protected)
Cannot have static members (except static final constants)

nested_classes — Classification of Nested Classes

Syntax

class Outer {
void display() {
class LocalInner {
void show() {
System.out.println("Inside Local Inner Class");
}
}
LocalInner obj = new LocalInner();
obj.show();
}
}

Explanation:

class LocalInner: Declares a local inner class inside the display() method. Its scope is limited to this method only.
void show(): A method defined inside the local inner class.
LocalInner obj = new LocalInner(); : Creates an object of the local inner class within the same method.
obj.show(); :Calls the method of the local inner class.

Java

class Outer {
    private int x = 10;

    void outerMethod() {
        int y = 20; // effectively final

        class LocalInner {
            void print() {
                System.out.println("x = " + x);
                System.out.println("y = " + y);
            }
        }

        LocalInner obj = new LocalInner();
        obj.print();
    }
}

public class Main {
    public static void main(String[] args) {
        Outer o = new Outer();
        o.outerMethod();
    }
}

Output

x = 10
y = 20

Explanation:

LocalInner is declared inside the outerMethod() method.
It accesses the instance variable x of the outer class.
It also accesses the local variable y, which is effectively final.
The local inner class cannot be accessed outside outerMethod().

When to Use Local Inner Class

When a class is required only within a single method.
When implementing complex logic locally without exposing it to the rest of the program.
As an alternative to anonymous inner classes when more structure is needed.

Note: Local inner classes are often replaced with lambda expressions in modern Java when implementing functional interfaces, but they are still important for understanding Java’s inner class concepts.

Local Inner Class in Java

Syntax

When to Use Local Inner Class

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