Why does ArrayList return error: ArrayIndexOutOfBoundsException

Question

I don't know why it is. I read my text file line by line, cut the line by split and save them to an ArrayList. But my program can't work if the file longer than 100 lines,so it returns an error at split command. I wonder if my computer is out of memory?

Everybody, who can make it obvious? thank you in advanced. Here is my code:

import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.Collections;
import javax.swing.JOptionPane;
class Vocab implements Comparable<Vocab>{
    private String vocab;
    private String explanation;
    public Vocab(String vocab, String explanation) {
        this.vocab = vocab;
        this.explanation = explanation;
    }
    public int compareTo(Vocab that){
        return this.vocab.compareTo(that.vocab);
    }    
    public String getVocab() {
        return vocab;
    }
    public void setVocab(String vocab) {
        this.vocab = vocab;
    }
    public String getExplanation() {
        return explanation;
    }
    public void setExplanation(String explanation) {
        this.explanation = explanation;
    }
}
public class Test {
    public static void readFile(String fileName, ArrayList<String> a) throws FileNotFoundException {
        try {
            File fileDir = new File(fileName);
            BufferedReader in = new BufferedReader(
                new InputStreamReader(
                    new FileInputStream(fileDir), "UTF8"));
        String str;
        while((str= in.readLine())!= null){
               a.add(str);                 
        }
        in.close();
        }         
        catch (IOException e) 
        {
            JOptionPane.showMessageDialog(null,"Something in database went wrong");
        }                    
    }        
    public static void main(String[] args) throws FileNotFoundException {
        // TODO code application logic here
        ArrayList<Vocab> a= new ArrayList<Vocab>();
        ArrayList<String> b= new ArrayList<String>();
        readFile("DictVE.dic",b);
        for (String t: b){
            String[] temp= t.split(":");
            a.add(new Vocab(temp[0].trim(), temp[1].trim()));// error in here
        }
    }    
}

and here is my file: DictEV.dic

@KevinEsche in each line of the file always have ":" character. I have defined it, you can look them in the end of my thread — My Will
– My Will, Commented Nov 10, 2015 at 15:10
@ParkerHalo i sure :). you can try with your computer. i put the file in the end of my thread :) — My Will
– My Will, Commented Nov 10, 2015 at 15:12

Andy Turner · Accepted Answer · 2016-09-19 09:03:50Z

4

There is a subtle gotcha in the String.split(String) method, which is that empty tokens are discarded from the end of the string:

Trailing empty strings are therefore not included in the resulting array.

So:

System.out.println("Hello:".split(":").length); // Prints 1.

You can keep the empty strings by passing a negative int as a second argument:

System.out.println("Hello:".split(":", -1).length); // Prints 2.

edited Sep 19, 2016 at 9:03

answered Nov 10, 2015 at 15:13

Andy Turner

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