/*
*不报错的写法
*/

public static void getSummeVonXijMalDifferenzMalwg() throws FileNotFoundException, IOException{
        getProdukt();
        double[] sum = new double[windowSize];
        int j = 0;
       
        while(j < windowSize){
            for(int i = 0; i < myArray.length; i++){
                 sum[j] = sum[j] + myArray[i][j]; // sum of myArray's rows
                 //这里就不报错。
            } 
            j++;
        }
    }

/*
*这个报错程序要如何修改才能成功运行？为了提高速度，我需要这种static全局的写法
*/
public static double[] sum = new double[windowSize];
    
.....
public static void getSummeVonXijMalDifferenzMalwg() throws FileNotFoundException, IOException{
        getProdukt();
        
        int j = 0;
       
        while(j < windowSize){
            for(int i = 0; i < myArray.length; i++){
                 sum[j] = sum[j] + myArray[i][j]; // sum of myArray's rows
                 //上面这行报错
            } 
            j++;
        }
    }