Accumulator Counting Tutorial

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You may find the page on accumulating variables useful:

How many countries in Asia?

In this example we use an accumulator to count the countries in Africa. Notice that acc shows up three times:

  • The accumulator acc is set to zero at the start.
int acc = 0;
  • Every time we encounter Africa we increment acc.
  if (region.equals("Africa"))
  {
    acc++;
  }
  • After the loop has completed acc contains the value we want - so we print it.
System.out.println(acc);

Change the program so that it counts the countries of Asia. Do NOT include the countries of Southeast Asia.

The accumulating variable is a very common trick in programming. The accumulator builds up the values - so that it is "right-so-far". For example in this program acc always holds the number of countries in Africa in the lines that have been read so far.

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How many big countries?

The example program counts the countries that have a population of more than 200 million.

Count the number of countries with an area of more than 1500000.

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Numbering countries.

Produce a numbered list of countries:

1 Afghanistan
2 Albania
3 Algeria
...
262 Zimbabwe

Use three character spaces for the number and put a single space after it.

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Country number 42.

Print the name of country number 42

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