programming – silveira neto

2 unit tests, 0 integration tests

Published by Silveira on 27 March, 2017

Found on reddit

Cedilha no Ubuntu 16.04

Published by Silveira on 5 March, 2017

    çççç
  ççç  ççç 
  ççç  ççç 
  ççç 
  ççç 
  ççç  ççç 
    çççç
     çç
    çç

Fiz esse script (cedilha.sh) pra fazer o c-cedilha (ç) funcionar no Ubuntu 16.04. Como é uma tarefa chata que eu já tive que fazer muitas vezes fica mais fácil pra mim ter um script pra fazer isso e pode ser que seja útil a outras pessoas. Infelizmente é uma solução que exige baixar e executar como root um script da internet. Eu recomendo que você leia o script e entenda o que está acontecendo antes de executá-lo. Esse script altera vários arquivos importantes e ele faz um backup (.bak) desses arquivos.

wget https://raw.githubusercontent.com/silveira/cedilha.sh/master/cedilha.sh
sudo bash cedilha.sh

Por favor, se o script funcionou pra você também, diga nos comentários. Se você não está usando Ubuntu 16.04 e quer testar o script ainda assim, edite o script e remova a verificação no inicio do programa.

parallel counting in Java using AtomicInteger

Published by Silveira on 30 September, 2015

import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.concurrent.TimeUnit;

class ParallelCounterExample {
   public static void main(String[] args) throws InterruptedException {
      int threads = 2000;
      ExecutorService executor = Executors.newFixedThreadPool(threads);
      final AtomicInteger atomi = new AtomicInteger();
      for(int i=0; i<threads; i++) {
         executor.execute( new Runnable() {
            @Override
            public void run() {
               atomi.getAndIncrement();
            }
         });
      }
      executor.awaitTermination(1, TimeUnit.SECONDS);
      executor.shutdown();
      System.out.println(atomi.get());
    }
}

Regex with negatives lookahead and lookbehind

Published by Silveira on 22 June, 2015

"Looking different directions" by Paul Kline at (https://www.flickr.com/photos/paulelijah/6717953239/) — “Looking different directions” by Paul Kline.

Problem: Match strings that contains a single quotation mark ('), but not multiple ones together.

Solution:

(?<!')'(?!')

This is a regex for a single quotation mark with a (?<!') in the left and a (?!’) in the right. The (?<!') is a ?< look behind if not ! a single quotation mark '. The (?!') is a look ahead ? if not ! a single quotation mark '.

Java code:

import java.util.regex.Pattern;

public class RegexProblem {
  public static void main(String args[]) {
    Pattern single_quote = Pattern.compile("(?<!')'(?!')");
    String[] phrases = {
      "",
      "'",
      "a'a",
      "aaa",
      "aa'aa",
      "aa''aa",
      "aa'''aaa",
      "aaa''''aaa"
    };
    for(String phrase: phrases){
      System.out.println(String.format("For %s is %s.", phrase,
            single_quote.matcher(phrase).find()));
    }
  }
}

The output is:

For  is false.
For ' is true.
For a'a is true.
For aaa is false.
For aa'aa is true.
For aa''aa is false.
For aa'''aaa is false.
For aaa''''aaa is false.

Java, printing arrays

Published by Silveira on 5 June, 2015

As I keep forgetting, this post is to remind me that Java Java doesn’t have a pretty toString() for arrays objects, and it does for Lists.

import java.util.List;
import java.util.ArrayList;
import java.util.Arrays;

public class ListsExample {
    public static void main (String args[]) {
        // as an array
        String[] list1 = {"a","b","c"};
        System.out.println(Arrays.toString(list1));
        
        // as an List provided by Arrays
        List<String> list2 = Arrays.asList("d", "e", "f");
        System.out.println(list2);

        // as an implementation of the interface List
        // ArrayList (could also be LinkedList, Vector, etc)
        List<String> list3 = new ArrayList<String>();
        list3.add("g");
        list3.add("h");
        list3.add("i");
        System.out.println(list3);
    }
}