Java problem called climb (not from the website)

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I have a problem with a java problem. The problem is, You have a input file called climb.dat, inside the data file is: 3 2 5 8 The output is to have a left angled triangle with the data. One thing I do know is that the first number,(3), is how many left angled triangles and every triangle is supposed to be made up of a character which is c. How its supposed to look like is like this: c cc c cc ccc cccc ccccc c cc ccc cccc ccccc cccccc ccccccc cccccccc I don't how to solve this problem. I need help!!

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Level 0 , United Kingdom

13 January, 02:23

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Thomas

Level 41 , Bayreuth, Germany

11 January, 07:52

useful

are you sure about the first number? My guess would have been it represents the char to output in the triangles.

public class Main {
    // path to climb.dat
    private static final String FILE = "climb.dat";

    public static void main(String[] args) throws IOException{
        // read file contents into a list, convert to Int, no error checking
        List<Integer> content = readNumbers();
        // 'cast' the first number in a char starting at a for the input 1
        char c = (char) ('a' - 1 + content.get(0));

        // loop over the other numbers and call an output method
        for (int n : content.subList(1, content.size()))
            printTriangle(c, n);
    }

    // in the output method the passed number n stands for the number of rows to print (outer loop)
    // the inner loop is dependent on the outer loops current iteration
    private static void printTriangle(char c, int n) {
        for (int i = 0; i < n; i++) {
            for (int j = 0; j < i + 1; j++) {
                System.out.print(c);
            }
            System.out.println();
        }
    }

    // read the content of the file into a List<Integer
    private static List<Integer> readNumbers() throws IOException {
        try (Stream<String> lines = Files.lines(Paths.get(FILE))) {
            return lines
                    .map(Integer::parseInt)
                    .collect(Collectors.toList());
        }
    }

alejandro martinez

Level 1 , United States

11 January, 22:56

Hi Thomas, as for your question, yes I am sure about the first number. I also tried your code and it's giving me an error saying "the target type of this expression must be a functional interface".

Thomas

Level 41 , Bayreuth, Germany

12 January, 07:27

the necessary imports:

import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.util.List;
import java.util.stream.Collectors;
import java.util.stream.Stream;

You also can change the way of reading the file to what you're familiar with. It just reads the file, converts each line to an Integer, adds it to a list and finally returns that list.

List<Integer> numbers = new ArrayList<>();
try (BufferedReader in = new BufferedReader(new FileReader(FILE))) {
// or: try (BufferedReader in = Files.newBufferedReader(Paths.get(FILE))) {
    while (in.ready())
        numbers.add(Integer.parseInt(in.readLine()));
}
return numbers;

The first number imho is then a redundant information (?) as the following numbers each represents a triangle. In that case you can just ignore it or (but why when there is no additional content in the file) use it in the read loop to read a specific amount of lines/ numbers.

Alex

Level 1 , Mission, United States

12 January, 21:32

it is giving me an error in the part that goes, " return lines.map(Integer::parseInt "

Thomas

Level 41 , Bayreuth, Germany

12 January, 21:48

I've tested this with Java 8, 17 and 19 so either use correct imports (as written above) or one of the alternatives I described (again see my 2nd post here) or instead of a method reference use a lambda like

.map(l -> Integer.parseInt(l))

then there is no chance of an ambiguous call. (best would be to use the alternative in my second post)