Question

i have this code:

public class Test{
        arrayList<String> list = new ArrayList<String>();
        String[][] temp_list;

        public static void main(String[] args)
        {
          String temp = list.get(0);
          temp_list[0] = temp.split(" ");
        }
    }

i want to transfer the first item in ‘list’ into temp_list[0].compiling is success but i got error when i run it.this is the error:

 Exception in thread "main" java.lang.NullPointerException
            at Test.main(Test.java:this line=>temp_list[0] = temp.split(" ");)

anyone can help me?

Answer 1

This is because you haven’t allocated any 2D-array for temp_list. (Which array should the result of split be stored in?)

Here’s a working version of your snippet.

import java.util.ArrayList;

public class Test {
    static ArrayList<String> list = new ArrayList<String>();
    static String[][] temp_list;

    public static void main(String[] args) {
        list.add("hello wold");

        // allocate memory for 10 string-arrays.
        temp_list = new String[10][];     <-----------

        String temp = list.get(0);
        temp_list[0] = temp.split(" ");
    }
}