当出现空格时，在Java中用空格分割字符串？

Question

I'm trying to extract data from a CSV file, in which I have the following example CSV

timestamp, Column1,column2,column3
2019-05-07 19:17:23,x,y,z
2019-03-30 19:41:33,a,b,c
etc.

currently, my code is as follows:

public static void main(String[]args){
        String blah = "file.csv";
        File file = new File(blah);
        try{
            Scanner iterate = new Scanner(file);
            iterate.next(); //skips the first line
            while(iterate.hasNext()){
                String data = iterate.next();
                String[] values = data.split(",");
                Float nbr = Float.parseFloat(values[2]);
                System.out.println(nbr);
            }

            iterate.close();
        }catch (FileNotFoundException e){
            e.printStackTrace();
        }
    }

However, my code is giving me an error

java.lang.ArrayIndexOutOfBoundsException: Index 3 is out of bounds for length 3

My theory here is the split is the problem here. As there is no comma, my program thinks that the array ends with only the first element since there's no comma on the first element (I've tested it with the timestamp column and it seems to work, however, I want to print the values in column 3)

How do I use the split function to get the column1, column2, and column3 values?

Answer 1

import java.util.*;    
import java.util.*;     
import java.io.*;  
public class Sample  
{  
public static void main(String[] args)   
{  
String line = "";  
String splitBy = ",";  
try   
{  int i=0;
String file="blah.csv";   
BufferedReader br = new BufferedReader(new FileReader(file));    
int iteration=0;   
while ((line = br.readLine()) != null)   //returns a Boolean value  
{  if(iteration < 1) {  
  iteration++;     
  continue;}   //skips the first line
String[] stu = line.split(splitBy);    
String time=stu[3];   
System.out.println(time);   
 }   
}    
catch (IOException e)      
{     
 e.printStackTrace();    
 }} }    

Try this way by using BufferedReader
Input:

timestamp, Column1,column2,column3    
2019-05-07 19:17:23,x,y,z    
2019-03-30 19:41:33,a,b,c    
2019-05-07 19:17:23,x,y,a    
2019-03-30 19:41:33,a,b,f    
2019-05-07 19:17:23,x,y,x    
2019-03-30 19:41:33,a,b,y    

Output for this above code is:

z   
c   
a   
f
x
y

Answer 2

A few suggestions:

1. Use Scanner#nextLine and Scanner#hasNextLine .
2. Use try-with-resources statement.
3. Since lines have either whitespace or a comma as the delimiter, use the regex pattern, \\s+|, as the parameter to the split method. The regex pattern, \\s+|, means one or more whitespace characters or a comma. Alternatively, you can use [\\s+,] as the regex pattern.

Demo:

import java.io.File;
import java.io.FileNotFoundException;
import java.util.Arrays;
import java.util.Scanner;

public class Main {
    public static void main(String[] args) throws FileNotFoundException {
        String blah = "file.csv";
        File file = new File(blah);
        try (Scanner iterate = new Scanner(file)) {
            iterate.nextLine(); // skips the first line
            while (iterate.hasNextLine()) {
                String line = iterate.nextLine();
                String[] values = line.split("[\\s+,]");
                System.out.println(Arrays.toString(values));
            }
        }
    }
}

Output:

[2019-05-07, 19:17:23, x, y, z]
[2019-03-30, 19:41:33, a, b, c]