What is the nature of recursive calls in Java functions?

Recursion in Java is essentially the function call itself. This call can be achieved by direct call or indirect call. A typical example of recursion is calculating factorial, which is done by calling itself repeatedly until a termination condition is reached. Another practical example is generating the Fibonacci sequence, which is calculated by calling itself indirectly and returning the sum of the first two numbers.

The essence of recursive calls in Java functions

Recursion, in computer science, refers to the process of a function calling itself within a function. In Java, recursive functions are implemented by calling themselves.

The essence of recursion

The essence of recursion is that a function calls itself. This call can be made in two ways:

• Direct call: The function calls itself directly.
• Indirect call: A function calls itself through another function.

Recursive example

The following is an example of a Java function that calculates factorial:

public static int factorial(int n) {
    if (n == 0) {
        return 1;
    } else {
        return n * factorial(n - 1);
    }
}

In this example, factorial The function calls itself directly to calculate the factorial. When n equals 0, the recursion stops and 1 is returned. Otherwise, the recursion continues, returning n times the factorial of n-1, and so on until n equals 0.

Practical Case: Fibonacci Sequence

The Fibonacci Sequence is a sequence defined by the following rules:

• before The two numbers are 0 and 1.
• Each subsequent number is the sum of the previous two numbers.

We can use recursion to calculate the Fibonacci sequence:

public static int fib(int n) {
    if (n == 0) {
        return 0;
    } else if (n == 1) {
        return 1;
    } else {
        return fib(n - 1) + fib(n - 2);
    }
}

In this example, the fib function indirectly calls itself and returns the first two The sum of Fibonacci numbers to calculate Fibonacci numbers. When n equals 0 or 1, the recursion stops and the corresponding value is returned. Otherwise, the recursion continues, returning the sum of the Fibonacci numbers of n-1 and n-2.

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