這段代碼有什麼問題？得到0作爲答案

Question

public class Sum { 
public static void main(String[]args){ 
    int sumOfPos = 0; 
    int sumOfNeg = 0; 
    int sum = sumOfPos + sumOfNeg; 
//should give 1 , 5 , 9 
     for(int pos = 1 ; pos<= 9; pos+=4){ 
      int Old = pos*pos; 
      sumOfPos = pos + Old; 
     } 
//should give -3 and -7 
     for(int neg = -3 ; neg>= -7; neg-=4){ 
      int Old = neg*neg; 
      sumOfNeg = neg + Old; 
     } 
// should give the sum of the sqaure of these numbers 
    System.out.println(sum); 
} 

我得到零是什麼問題？ 我只能用這個for循環。 獲得所需結果的其他方法是什麼？

Answer 1

public class Sum { 
    public static void main(String[]args){ 
     int sumOfPos = 0; 
     int sumOfNeg = 0; 
//should give 1 , 5 , 9 
    for(int pos = 1 ; pos<= 9; pos+=4){ 
     int Old = pos*pos; 
     sumOfPos = pos + Old; 
    } 
//should give -3 and -7 
    for(int neg = -3 ; neg>= -7; neg-=4){ 
     int Old = neg*neg; 
     sumOfNeg = neg + Old; 
    } 
// should give the sum of the sqaure of these numbers 
int sum = sumOfPos + sumOfNeg; 
System.out.println(sum); 

}