Rezha Julio

Hi!
My name is Rezha Julio
I am a chemist graduate from Bandung Institute of Technology. Currently working as Data Engineer at Traveloka.
You can reach me by email:

contact@rezhajulio.id

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Python Data StructureGet more with collections!

time to read 1 min | 97 words

In addition to Python’s built-in data structures (such as tuples, dicts, and lists), a library module called collections provides data structures with additional features, some of which are specializations of the built-in ones.

Import the module:

import collections

Specialized container datatypes are usually dict subclasses or wrappers around other classes like lists, tuples, etc.

Notable implementations are :

  • the Counter class used for counting hashable objects.
  • defaultdict class used as a faster implementation of a specialised dictionary.
  • namedtuple class used for defining a meaning for every position in a tuple, often useful with databases or CSV files.

Java 101Translating Scanner tokens into primitive types

time to read 1 min | 133 words

The Scanner class can be used to break an input into tokens separated by delimiters. Scanner also has methods to translate each token into one of Java’s primitive types.

Delimiters are string patterns and are set in the following way:

Scanner s = new Scanner(input);
s.useDelimiter(pattern);

If we need to read a file containing a set of integers, and calculate the total, we can use Scanner’s nextInt method:

int sum = 0;
//create a new instance of Scanner
Scanner s = new Scanner(
  new BufferedReader(
    new FileReader("in.txt")));
/*tokenize the input file and 
convert to integers*/
while (s.hasNext()) {
  if (s.hasNextInt()) {
    sum += s.nextInt();
  } else {
    s.next();
  }   
}

In the example above, we iterate through the file, tokenizing each value and converting it to an integer before adding it to sum.

Java 101Listing a file system's root directories

time to read 1 min | 77 words

Using the static FileSystems class, you can get the default FileSystem (note the missing s) through the getDefault() method.

The getRootDirectories() method of FileSystem can be used to acquire a list of root directories on a file system.

An object of type Iterable is returned, so the directories can be iterated over in the following way:

FileSystem sys = FileSystems.getDefault();
Iterable<Path> d = sys.getRootDirectories();
for (Path name: d) {
    System.out.println(name);
}

This is available from Java 1.7.

Java 101The Console class

time to read 1 min | 110 words

The Java.io.Console class provides methods to access the character-based console device, if any, associated with the current Java Virtual Machine. This class is attached to the System console internally.

Console class provide means to read text and passwords from the console.

To read a line as a String:

Console console = System.console();
String myString = console.readLine();

To read a password as an array of chars:

Console console = System.console();
char[] pw = console.readPassword();

If you read passwords using Console class, it will not be displayed to the user.

Keep in mind that this class does not have a high level of security and it is mostly used at development stage.

RECENT SERIES

  1. java 101 (13):
    Apr 29, 2017 - Translating Scanner tokens into primitive types
  2. python data structure (5):
    May 03, 2017 - Enhance your tuples
  3. python function (2):
    Apr 16, 2017 - Lambda Functions in Python
  4. python generator (4):
    Apr 26, 2017 - Next, Function or Method ?

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