Java beginners (17) Recursion

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To put it bluntly, you can call yourself until the method body does not conform to the conditions.

All the methods you have seen so far can call other methods. However, a method can also call itself. We call this call as a recursion. Obviously. You must include some logical judgments in the recursive method so that you can stop calling itself at the end. We will use a simple example to introduce its implementation process. We can write a method to calculate the integer power of a variable, that is, to calculate the Npower of x or x *... * X, that is, x is multiplied by its own n times. We can apply this formula to obtain the result, that is, the Npower of x is equal to the (n-1) Power of x multiplied by x.

Here is a complete program containing the recursive method power:


Public class PowerCalc
{
Public static void main (string [] arga)
{
Double x = 5.0
System. out. println (x + to the power 4 is + power (x, 4 );
System. out. println (7.5 to the power 5 is # power (7.5, 5 ));
System. out. println (7.5 to the power 0 is # power (7.5, 0 ));
System. out. println (10 to the power-2 is # power (10,-2 ));
)
// Raise x to the power n
Static double power (double x, int n)
{
It (n> 1)
Return x * power (x, n = 1); // Recersive call
Else if (n <0)
Return 1.0/power (x, n); // Negative Dower of x
Else
Return n = 0? 1.0: x; // when n is return 1. otherwise x
}
}
The output result of this program is:
5.0 to the power 4 is 625.0
7.5 to the power 5 is 23730.46875
7.5 to the power 0is 1.0
10 to the power-2 is 0.01