java 关于递归的一个问题

/*  * num为0到100 即表示0%-100%  
*/ public static Boolean probability(int num) {    
    int flag = random.nextInt(100) +1 ;  
    if (flag <= num)   return true; 
    return false; 
  }  
  //递归
   public static int recursion(int flag,int nature){  
     if(probability(flag)){  
        nature+=1;   
        System.out.println("nature="+nature);   
        recursion(flag,nature);  
     }  
     return nature; 
  }  
  public static void main(String[] args) {  
         System.out.println(recursion(50,0));          
  }

怎么会出现这样的运行结果
nature=1
nature=2
1
个人认为应该为
nature=1
nature=2
2 Java 递归
[解决办法]
nature+=1;???
????????System.out.println("nature="+nature);???
????????recursion(flag,nature);?
=========================================
nature = recursion(flag,nature);
[解决办法]
public static int recursion(int flag,int nature)
========================================
替归只是一个方法调用本身，你怎么强加意志让这个变量等于你第二次计算的值？