SquareWithDiagonalImpl

// JUnit test class:
//  https://pastebin.com/yCnsggc2

import java.util.stream.Collectors;
import java.util.stream.IntStream;

public class SquareWithDiagonalImpl {

    // Hard-coded implementation:
    public static void main(String[] args) {
        System.out.println("00000");
        System.out.println("01000");
        System.out.println("00200");
        System.out.println("00030");
        System.out.println("00004");
    }

    public static void simplisticImplementation_withSeparatePrintStatements(final int size) {
        for (int lineIndex = 0; lineIndex <= size; ++lineIndex) {
            for (int columnIndex = 0; columnIndex <= size; ++columnIndex) {
                if (lineIndex == columnIndex) {
                    System.out.print(lineIndex);
                } else {
                    System.out.print("0");
                }
            }
            System.out.println();
        }
    }

    public static void simplisticImplementation_withTernaryOperator(final int size) {
        for (int lineIndex = 0; lineIndex <= size; ++lineIndex) {
            for (int columnIndex = 0; columnIndex <= size; ++columnIndex) {
                System.out.print((lineIndex == columnIndex) ? lineIndex : "0");
            }
            System.out.println();
        }
    }

    public static void streamImplementation(final int size) {
        IntStream.rangeClosed(0, size).mapToObj((lineIndex) ->
                IntStream.rangeClosed(0, size).mapToObj((columnIndex) ->
                        (lineIndex == columnIndex) ? String.valueOf(lineIndex) : "0"
                ).collect(Collectors.joining())
        ).forEach(System.out::println);
    }

}