Java：不等分线

Question

I tried looking for answers online, but I don't know how to word it correctly to find what I'm looking for. I have a file that I need to split but some lines are missing the regex I am trying to use. The file I need to split looks like this:

A,106,Chainsaw 12"
D,102
d,104
a,107,Chainsaw 10"

I need to split it in three different sections, Letter, ID, Tool but 102 and 104 are missing the comma and Tool section. I've tried:

String[] sec = line.split(",");

and

String[] sec = line.split(",| \n");

And several other regex combinations, but none of them work. I get an AOB error on the line such as (below) because its missing.

...[0];
...[1];
String tool = sec[2]; //here

Any help is appreciated

Answer 1

Use String[] sec = line.split(","); and then test the length of the sec array

If you have 2 then you can use sec[0] and sec[1] but if you have 3 you can also use sec[2] If you have 0 then you have a empty line

Answer 2

You were on the right path with

String[] sec = line.split(",");

This function will return an Array with (in your example) either 2 or 3 elements. Then you could simply check for the length of the array

String[] sec = line.split(",");
int length = sec.length;

Here you can see what type of entry you have. Either length will be 2, which mean that it is a letter-ID pair, or it is 3, which means it is a letter, Id and tool entry.

If you need to be able to distinguish between more categories, you will have to put in an extra check. For example: Lets say your entry can be missing out one of the other two elements (not only the tool) and you could encounter an entry like:

a,Chainsaw 10

In this case you will furthermore need to read out the type of the single elements. The first thing that comes to my mind is, that you could check the first element in your array and check its length (should always be 1, since it is just a letter) and parse the second one into Integer (I assume id is always a number)

Answer 3

You are splitting on , and you have cases where input string is not present in same pattern.

So for this knid of situation, after splitting the string, every-time you have to check for the array length.
If it's less than desired length, then you cannot access desired element, because it's not present in the array.

For example:

• When you do String[] sec = line.split(","); for A,106,Chainsaw 12 , you will have 3 length, and you can access elements like sec[0],sec[1],sec[2] .
• When you split A,106 , then you will get 2 as length, and elements present in the array are going to be sec[0],sec[1] .

Example code:

import java.util.*;
public class ArrayListDemo {

   public static void main(String args[]) {
     ArrayList<String> lines= new ArrayList<String>();
         lines.add("A,106,Chainsaw 12");
         lines.add("A,106");
          lines.add("A");

       for(String str:lines){
         String[] parts = str.split(",");
         if(parts.length<2){
             for(int i = 0 ; i < parts.length ; i++)
             System.out.println("Splitted Item at index " + "[" + i + "]" + "::" + parts[i]);
         }else{
             for(int i = 0 ; i < parts.length ; i++)
             System.out.println("Splitted Item at index " + "[" + i + "]" + "::" + parts[i]);
         }
       }


   }
}

Hope that helps..