斐波那契数列算法实现

package ch06;

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

递归算法实现

package ch06;

public class Recursion {
    public static void main(String[] args) {
        test2(100);
    }

    public static void test() {
        System.out.println("Hello,World!");
        test();
    }

    public static void test2(int n) {
        if(n == 0) {
            return;
        }
        System.out.println(n); 
        test2(n - 1);
    }
}

求和算法实现

package ch06;

public class Triangle {

    public static int getNumber(int n) {
        int total= 0;
        while(n > 0) {
            total = total + n;
            n--;
        }
        return total;
    }

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