在Java中将输入字符串转换为具有可变长度的int数组

Question

Here is a snippet of my code. I want to get of user a number with variable length and convert it to int array. example: input: 352040 , output:{3,5,2,0,4,0}

  Scanner in = new Scanner(System.in); 
    System.out.println(" Enter your size number: ");
         int length = in.nextInt();

    System.out.println(" Enter a number: ");
         int number = in.nextInt();

         int[] intArray = null;
         String str = Integer.toString(number);

         for ( int i =0; i < length ;i++)
           intArray[i] = Integer.parseInt(String.valueOf(str.charAt(i)));


           System.out.println(Arrays.toString(intArray));

This comes up with an error(Exception in thread "main" java.lang.NullPointerException) and I cant understand why.

Thanks for any help.

Answer 1

Agree with comments, split("") will work only on javascript here is a code snippet that does what OP wants...

  String s = "352040";
  int[] intArray = new int[s.length()];
  for(int i = 0; i < s.length(); i++) {
      intArray[i] = Integer.valueOf(s.substring(i, i+1));
  }  
  System.out.println(Arrays.toString(intArray));

Answer 2

having an object array needs to go through 2 steps. you failed to cover the second step.

1. Declaring a Variable to Refer to an Array

The preceding program declares an array (named anArray) with the following line of code:

// declares an array of integers int[] anArray;

2. Creating, Initializing, and Accessing an Array

One way to create an array is with the new operator . The next statement in the ArrayDemo program allocates an array with enough memory for 10 integer elements and assigns the array to the anArray variable.

// create an array of integers anArray = new int[10]; If this statement is missing, then the compiler prints an error like the following, and compilation fails:

ArrayDemo.java:4: Variable anArray may not have been initialized.

How to resolve your issue:

instead of your array variable point to null, point to an array object by creating it like:

int[] intArray = new int[length];

Answer 3

You need to create the array first.

     int[] intArray = new int[length];  // Create array
     String str = Integer.toString(number);

     for ( int i =0; i < length -1;i++) 
       intArray[i] = Integer.parseInt(String.valueOf(str.charAt(i)));