NumberFormatException：对于输入字符串：“”，在解析时

Question

I wished to turn a string of single digit integers into an Integer ArrayList, and I'm getting a very odd exception. Here's the sample code:

    Scanner test = new Scanner(System.in);
    String[] temp = null;
    String line = null;
    ArrayList<Integer> artemp = new ArrayList<>();

    while(test.hasNext()) {
        line = test.next();
        temp = line.split("");
        for(int i = 0; i < temp.length; i++)
        artemp.add(Integer.parseInt(temp[i]));
        for(int i : artemp) System.out.println(i);

    }

It is basically supposed to read the string of ints from stdin, put them in an arraylist as primitives, and then print them out. Of course, this is just a small test case to which I narrowed down my larger error.

The exception this raises is the following:

Exception in thread "main" java.lang.NumberFormatException: For input string: ""
    at java.lang.NumberFormatException.forInputString(NumberFormatException.java:65)
    at java.lang.Integer.parseInt(Integer.java:504)
    at java.lang.Integer.parseInt(Integer.java:527)

As far as I can see, the following should take place:

1. line takes in stdin
2. temp gets filled with each of the individual single-digit values (split("") splits after every character)
3. Each digit (stored as a String ) is parsed as an int and added to artemp
4. Print out each digit.

What exactly is going wrong here? If I print out temp with the following code:

for(String s : temp) System.out.println(s);

Then the digits get printed successfully (as Strings), and I there are no extra characters. How exactly could parseInt(temp[i]) be getting applied to the string "" ?

Answer 1

First of all I'm suspecting your split,

  temp = line.split("");

If you want to split with space ,it should be

  temp = line.split(" ");

And if you want with "" only,then here is the cause.

There is nothing to do with conversion.

There are some empty strings in you array .

So exception while converting empty string in to integer.

here

 artemp.add(Integer.parseInt(temp[i]));

What you can do is,check the data before parsing.

if(temp[i]!=null && !temp[i].isEmpty()){
          artemp.add(Integer.parseInt(temp[i]));
}

Answer 2

From The Docs parseInt

Throws:
    NumberFormatException - if the string does not contain a parsable integer.

So your Code artemp.add(Integer.parseInt(temp[i])); is some where encoutering a unparsable String.

Answer 3

您的split（“”）为null，您应该编写split（“”）（带引号的双引号）

Answer 4

Rather than using split, I'd think using the string itself will be better. Try this.

Scanner test = new Scanner(System.in);
String[] temp = null;
String line = null;
ArrayList<Integer> artemp = new ArrayList<>();

while(test.hasNext()) {
    line = test.next();
    for(int i = 0; i < line.length; i++)
        artemp.add(Integer.parseInt(""+line.charAt(i));
    for(int i : artemp) System.out.println(i);
}