递归之斐波那契数列java的3种方法

public class Demo {    public static void main(String[] args) {     int num1 = 1;     int num2 = 1;     int num3 = 0;     System.out.println(num1);     System.out.println(num2);     for (int i = 1; i < 10; i++) {        num3 = num1 + num2;       num1 = num2;                                                                num2 = num3;       System.out.println(num3);     }   }            } 

public class DIGUI1 {     public static void main(String[] args) {     int []arr=new int[20];      arr[1]=1;      arr[2]=1;      System.out.print(" "+arr[1]);      System.out.print(" "+arr[2]);     for(int i=3;i<20;i++){        arr[i]=arr[i-1]+arr[i-2];       System.out.print("  "+arr[i]);     }   }  } 

public class Demo {    public static int f(int n) throws Exception {     if(n==0){       throw new Exception("参数错误！");     }     if (n == 1 || n == 2) {       return 1;     } else {       return f(n-1)+f(n-2);//自己调用自己     }  }     public static void main(String[] args) throws Exception {     for (int i = 1; i <=10; i++) {       System.out.print(f(i)+" ");     }   }  }