What is the difference between recursive and tail recursive calls in Java functions?

Tail recursive calls will not create a new function stack frame, and recursive calls can be optimized to avoid stack space exhaustion. In the actual case, the factorial calculation function was optimized by introducing an auxiliary function to convert the original recursive call into a tail recursive call.

Recursive calls and tail recursive calls in Java functions

Recursive calls

• The function calls itself within itself.
• Each recursive call will create a new function stack frame.
• Recursive calls can cause stack space to be exhausted, especially when recursing deeply.

Tail recursive call

• The function calls itself within itself as the final operation.
• Tail recursive calls will not create a new function stack frame.
• Tail recursive calls can avoid stack space exhaustion.

Practical case

The function that calculates the factorial can be used as an example of a recursive call:

public static int factorial(int n) {
  if (n == 0) {
    return 1;
  }
  return n * factorial(n - 1);  // 递归调用
}

In order to convert it into a tail recursive call , you can introduce an auxiliary function:

public static int factorialTail(int n, int result) {
  if (n == 0) {
    return result;
  }
  return factorialTail(n - 1, n * result);  // 尾递归调用
}

In a tail recursive call, the result variable stores the current factorial value, and the function is called recursively at the end of itself to avoid creating a new function stack frame .

Conclusion

Tail recursive calls can optimize recursive calls by avoiding the creation of new function stack frames. Although the Java virtual machine typically optimizes tail-recursive calls automatically, manually converting recursive calls to tail-recursive calls ensures optimal performance.

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