Reading a line from a text file and splitting its contents

Question

I have this kind of file structure

MALE:FooBar:32
FEMALE:BarFoo:23

Where I would want to identify the gender and age of person, <Gender>:<Name>:<age>

try{
 BufferedReader in = new BufferedReader(new FileReader("people.ser"));
 String s;
 while((s = in.readLine()) != null){
 String[] var = s.split(":");
 //var[0]=MALE etc etc
 addGender.add(var[0]);
 }
}catch(Exception e){
 e.printStackTrace();
}

• Is using a delimiter (like a : in this case) to split string considered a bad practice?
• What about using the array from the splitted string to store it in some place?
• Are there any alternatives and better file structure?

• cl-r: String.split(RegEx) is the now recommended for new Java'versions (StringTokenizer for old version compatibility). With 'palacsint' advices, you code look fine.

Answer 1

I don't think that using : is a bad practice but you have to escape it somehow if it occurs inside your data. Anyway, I'd consider using XML or JSON here.

Some notes about the code:

1. You should close the stream (in a finally block). See Guideline 1-2: Release resources in all cases in Secure Coding Guidelines for the Java Programming Language
2. The .ser file extension is often used for serialized Java objects. I'd use something else to avoid the possible confusion.

3. It's a good practice to set the character set when you read a text file. The used FileReader always uses the default charset which could vary from system to system. Consider using InputStreamReader and FileInputStream as the documentation of FileReader says. Here is an example:

   FileInputStream fileInputStream = null;
   InputStreamReader inputStreamReader = null;
   BufferedReader bufferedReader = null;
   try {
    fileInputStream = new FileInputStream("people.dat");
    inputStreamReader = new InputStreamReader(fileInputStream, "UTF-8");
    bufferedReader = new BufferedReader(inputStreamReader);
    // use BufferedReader here
   } finally {
    IOUtils.closeQuietly(bufferedReader);
    IOUtils.closeQuietly(inputStreamReader);
    IOUtils.closeQuietly(fileInputStream);
   }
   

   It uses IOUtils from Apache Commons IO and closes the FileInputStream even if the constructor of InputStreamReader or BufferedReader throws an exception.

• KyelJmD: How would I do number 3?
• palacsint: @KyelJmD: See the edit, please.
• KyelJmD: why did you use final?
• palacsint: @KyelJmD: final helps readers and maintainers, because they know that the reference always points to the same instance and it doesn't change later. programmers.stackexchange.com/questions/115690/… but you can find other questions on Programmers.SE in the topic.
• KyelJmD: I would place those final variables in the class? or inside a method that calls them?

Answer 2

Scanner is a bit easier to use then BufferedReader...

import java.io.File;
import java.io.FileNotFoundException;
import java.util.ArrayList;
import java.util.List;
import java.util.Scanner;
public class Main {
 public static void main(String[] args) { 
 try {
 File f = new File("people.ser");
 Scanner sc = new Scanner(f);
 List<Person> people = new ArrayList<Person>();
 while(sc.hasNextLine()){
 String line = sc.nextLine();
 String[] details = line.split(":");
 String gender = details[0];
 String name = details[1];
 int age = Integer.parseInt(details[2]);
 Person p = new Person(gender, name, age);
 people.add(p);
 }
 for(Person p: people){
 System.out.println(p.toString());
 }
 } catch (FileNotFoundException e) { 
 e.printStackTrace();
 }
 }
}
class Person{
 private String gender;
 private String name;
 private int age;
 public Person(String gender, String name, int age){
 this.gender = gender;
 this.setName(name);
 this.age = age;
 }
 /**
 * @return the gender
 */
public String getGender() {
 return gender;
}
/**
 * @param gender the gender to set
 */
public void setGender(String gender) {
 this.gender = gender;
}
/**
 * @param name the name to set
 */
public void setName(String name) {
 this.name = name;
}
/**
 * @return the name
 */
public String getName() {
 return name;
}
/**
 * @return the age
 */
public int getAge() {
 return age;
}
/**
 * @param age the age to set
 */
public void setAge(int age) {
 this.age = age;
}
public String toString(){
 return this.gender + " " + this.name + " " + this.age;
}
}

• Eva: toString() method should use StringBuilder instead of concatenation.
• Nihathrael: Since the toString() method is likely only used for debugging purposes, I'd say readability trumps performance here and the current implementation is a lot more readable. In case it is used in heavy iteration, that might be a different case.