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)+" "); 
    } 
  }  
}