对象明明不是null，一直出现NullPointerException异常

public class splitStringToDouble{
public static void main(String[] args){
String s="1,2,3;4,5,6,8;390;39";
splitStr(s);
}
static void splitStr(String str){
String[] splStr=str.split(";");

    String[][] splStrAg=new String[splStr.length][];
    double[][] d=new double[splStr.length][];
    for(int i=0;i<splStr.length;i++){
        splStrAg[i]=splStr[i].split(",");
    }
    for(int i=0;i<splStr.length;i++)
        for(int j=0;j<splStrAg[i].length;j++){
                System.out.print(splStrAg[i][j]+" ");
            if(splStrAg[i][j]==null){
                System.out.println("null");
            }
            try{
                    d[i][j]=Double.parseDouble(splStrAg[i][j]);
            }catch (NullPointerException e){

                System.out.println("a String is null");
            }
        }
}

}