recursion: method calls itself

public class Study05 {

public static void main(String[] args) {/*** recursion: the method calls itself** /** *1. What is recursion?* * is the method itself calling itself.*** *2.f(int n);*** *f(int n){* * f(n-1);//Direct call;* *}*** *f(int n){* * a(n);//Indirect call;* *}*** *a(int n){* * f(n-1);* *}*** *3. Calculate 5!* *5!=5*4!* *4!=4*3!* *3!=3*2!* *2!=2*1!* *1!=1;*** *public static int factorial(int n){*** * int result=n*factorial(n-1);*** * return result;* *}*** *4. Two elements of recursion:* * 1) Rules for method invocation itself;* * 2) The end condition of the recursion; if there is no end condition, there will be a stack overflow, java.lang.StackOverflowError.* *5. Advantages and disadvantages of recursion:* * 1) The idea is simple;* * 2) Every time a method is called, the stack memory is opened up; the memory consumption is large, which affects the performance; if the performance requirements are high, avoid using recursion.* *6. Features of recursion:* * 1) A problem can be decomposed into several sub-problems with the same level;* * 2) The solution of the outer layer problem depends on the solution of the inner layer problem;* * 3) The solution to the problem of each layer is consistent;* * 4) There must be an end condition.* * 5) Recursive problems can be solved with loops.*/System.out.println(sum(4));}//Use recursive method to find factorialpublic static int sum(int a) {int temp = 0;if (a == 1) {temp = 1;//End condition} else {temp = a * sum(a - 1);}return temp;}

}