package com.smbea.demo; 
 
public class Student { 
  private int sum = 0; 
 
   
  /** 
   * 递归求和 
   * @param num 
   */
  public void sum(int num) { 
    this.sum += num--; 
     
    if(0 < num){ 
      sum(num); 
    } else { 
      System.out.println("sum = " + sum); 
    } 
  } 
   
}

package com.smbea.demo; 
 
public class Test { 
 
  public static void main(String[] args) { 
    Teacher teacher = new Teacher(); 
    teacher.sum(); 
  } 
 
  public static int sum(int num){ 
    if(1 == num){ 
      return 1; 
    } else { 
      return num + sum(num - 1); 
    } 
  }; 
}