我仍然开始学习OOP,并且这个错误一直在我的代码中弹出;说Exception in thread "main" java.lang.NullPointerException
NullPointerException java错误
public class SlumbookDriver{
public static void main(String args[]){
Slumbook[] contacts = new Slumbook[19];
... // index is an int and is the value of the index of the array
... // i feed it to a function "void viewEntry" that just shows
// the other attributes of the class Slumbook
viewEntry(index, contacts);
}
}
然后我具备的功能VIEWENTRY
public static void viewEntry(int index, Slumbook[] contacts){
Scanner sc = new Scanner(System.in);
if(index == 0){
System.out.println("Array is empty");
}
else{
String id = contacts[index].getIdNo();
System.out.println("Please enter ID number");
String idNo = sc.next();
if(id != idNo){
while(id != idNo && index != -1){
index--;
id = contacts[index].getIdNo();
}
if(index == -1){
System.out.println("ID does not exist");
return; //terminate action since the ID number does not exist
}
}
System.out.println(contacts[index].viewDetails());
}
}
你可以发布更多的代码,以及堆栈跟踪打印与例外?这将有助于查明问题。 – Malt