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[英]Java - Null Pointer Exception when trying to add JLabel and/or JTextField to an array
[英]Null pointer exception when trying to parse array (java)
嘗試解析字符串數組索引時,出現了空指針異常。 我該如何解決? 謝謝
public class studentclass {
public static void main(String[] args){
Scanner scan = new Scanner(System.in);
String[][] student = new String[10][];
Double[][] results = new Double[10][];
Double[] total = new Double[10];
String tableln = "";
for(int index = 0; index < student.length; index++){
System.out.println("\nPlease enter student " + (index+1) + "'s details");
String userinput = scan.nextLine();
student[index] = userinput.split(",");
//converts string array in to double array but receiving null pointer exception
results[index][0] = Double.parseDouble(student[index][2]);
results[index][1] = Double.parseDouble(student[index][3]);
results[index][2] = Double.parseDouble(student[index][4]);
results[index][3] = Double.parseDouble(student[index][5]);
total[index] = (results[index][0]*0.1+results[index][1]*0.4+
results[index][2]*0.3+results[index][3]*0.2);
看起來results[index]
需要初始化。 您為帶有results[0..n]
new的results[0..n]
分配了內存,但沒有為results[index][0...n]
分配內存。
如果您始終存儲四個值,請添加以下內容:
results[index] = new Double[4];
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