9. Reading a Text File

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Let's read some data from an external source to combine all we learned before...

With a free online tool we create a test CSV file with random data. This file is stored in a subdirectory resources as testdata.csv.

The file in the source code contains comma-separated values for counter, firstname, lastname, age, Street, City, State, ZIP:

1,Ada,Gomez,40,Mabvob Pike,Radafso,LA,60500
2,Bernard,Jordan,28,Dotcu Court,Cewbufbim,MS,17422
3,Mittie,Vaughn,64,Nandac Mill,Patunif,RI,81182
4,Miguel,Clarke,39,Liac Boulevard,Deguci,NH,32207

Let's write a program to read this CSV-file line by line and convert each line to an object which is added to a list of persons:

Just like in the UsingObjects-example, we use an object to store the data of each line in the CSV file, in this case, the object Person.

Within the loadPersons-method:

  • the file is opened
  • read line by line
  • the text of each line is used to create a Person-object
  • this object is added to the list
  • the list is returned.

Within the main-method, the resulting list is used:

  • to count the number of persons on the list
  • to print each person's full name and age
$ java ReadTextFile.java
Number of persons loaded from CSV file: 100
Ada Gomez, age: 40
Bernard Jordan, age: 28
Mittie Vaughn, age: 64
Miguel Clarke, age: 39

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