Do Java functions support closures? How to implement closure?

Java does not support true closures, but they can be simulated through anonymous inner classes. Closures in anonymous inner classes can access external variables even if the function that created them has exited, but external variables cannot be declared or modified outside the function, and lambda expressions cannot capture external variables directly.

Closures in Java functions

Introduction to closures

A closure is a function that has access to the function that created it variables defined in. The closure can still access these variables even if the function that created it has finished executing.

Implementing closures in Java

Java does not support real closures. However, by using anonymous inner classes we can simulate the behavior of closures.

Practical Case

Consider the following code snippet:

public class LambdaClosure {

    public static void main(String[] args) {
        int x = 10;
        Runnable closure = () -> System.out.println(x);
        
        // 调用闭包
        closure.run();
    }
}

In this case:

• x is a local variable , which is defined in the main() method.
• Anonymous inner class Runnable is used to create closures.
• Closure closure Accessed external variable x even though the main() method has exited.

Advantages and Limitations

Advantages of mocking closures include:

• It allows access to external variables when needed.
• External variables can be captured in anonymous inner classes.

The limitations include:

• External variables cannot be declared or modified outside the function.
• lambda expression cannot capture external variables directly, and anonymous inner classes must be used.

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