Count specific condition in 2d-array

Question

Given a 2D Array, count the number data at column 3 where it is the same.

For example,

 String[][] array = {
                    { "red", "value1", "alpha"  },
                    { "blue", "value2", "alpha"  }, 
                    { "green", "value3", "alpha"  }, 
                    { "black", "value4", "alpha" },
                    { "grey", "value1", "beta"  },
                    { "white", "value2", "beta"  }, 
            };

          int counter=0;
          for(String[] subArray : array)
              for(String string : subArray)
                  if(string.toLowerCase().equals("beta"))
                      counter++;

          System.out.println(counter);

The output of the counter for beta = 2 and alpha = 4.

Assuming I don't know what is the exact name of the data in column 3, how I count the conditions? if(string.toLowerCase().equals(???))

Any help will be appreciated!

Hearen · Accepted Answer · 2018-08-17 03:02:35Z

2

It could be something like this using groupingBy in java 8:

 Arrays.stream(array)
       .collect(Collectors.groupingBy(arr -> arr[2], Collectors.counting()));

Result will:

{alpha=4, beta=2}

B.T.W If you want to ignore case, do it as:

Arrays.stream(array)
      .collect(Collectors.groupingBy(arr -> arr[2].toLowerCase(), Collectors.counting()));

answered Aug 17, 2018 at 3:02

Hearen

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Comments

Scary Wombat · Accepted Answer · 2018-08-17 02:58:24Z

1

Create a Map<String, int>

Look for the value of string.toLowerCase in the Map and if it is found increment the value of int else insert with the value of 1

answered Aug 17, 2018 at 2:58

Scary Wombat

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Comments

Jacob Gaiski · Accepted Answer · 2018-08-17 03:00:42Z

0

There are many ways, but one way:

Create a new multidimensional array of types string:int.
Iteratethrough your array at the last index, and then check if it exists in your array you made.
If it exists, inremement the int to int+1.
If it does not exist, add it and add int=1

answered Aug 17, 2018 at 3:00

Jacob Gaiski

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2 Comments

Scary Wombat Over a year ago

Create a new multidimensional array of types string:int How would you know how big to make this array? Easier to use a Map I think

Jacob Gaiski Over a year ago

True, though, by creating the function yourself you can learn the logic yourself in addition to perhaps expanding using more simpler means. But agreed there are lots of ways.

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