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jeremymarshall1's solution

to Diamond in the Java Track

Published at Oct 19 2019 · 0 comments
Instructions
Test suite
Solution

The diamond kata takes as its input a letter, and outputs it in a diamond shape. Given a letter, it prints a diamond starting with 'A', with the supplied letter at the widest point.

Requirements

  • The first row contains one 'A'.
  • The last row contains one 'A'.
  • All rows, except the first and last, have exactly two identical letters.
  • All rows have as many trailing spaces as leading spaces. (This might be 0).
  • The diamond is horizontally symmetric.
  • The diamond is vertically symmetric.
  • The diamond has a square shape (width equals height).
  • The letters form a diamond shape.
  • The top half has the letters in ascending order.
  • The bottom half has the letters in descending order.
  • The four corners (containing the spaces) are triangles.

Examples

In the following examples, spaces are indicated by · characters.

Diamond for letter 'A':

A

Diamond for letter 'C':

··A··
·B·B·
C···C
·B·B·
··A··

Diamond for letter 'E':

····A····
···B·B···
··C···C··
·D·····D·
E·······E
·D·····D·
··C···C··
···B·B···
····A····

Setup

Go through the setup instructions for Java to install the necessary dependencies:

https://exercism.io/tracks/java/installation

Running the tests

You can run all the tests for an exercise by entering the following in your terminal:

$ gradle test

Use gradlew.bat if you're on Windows

In the test suites all tests but the first have been skipped.

Once you get a test passing, you can enable the next one by removing the @Ignore("Remove to run test") annotation.

Source

Seb Rose http://claysnow.co.uk/recycling-tests-in-tdd/

Submitting Incomplete Solutions

It's possible to submit an incomplete solution so you can see how others have completed the exercise.

DiamondPrinterTest.java

import org.junit.Ignore;
import org.junit.Before;
import org.junit.Test;

import java.util.List;

import static java.util.Arrays.asList;
import static java.util.Collections.singletonList;
import static org.hamcrest.CoreMatchers.is;
import static org.junit.Assert.assertThat;

public class DiamondPrinterTest {

    private DiamondPrinter diamondPrinter;

    @Before
    public void setUp() {
        diamondPrinter = new DiamondPrinter();
    }

    @Test
    public void testOneByOneDiamond() {
        List<String> output = diamondPrinter.printToList('A');
        assertThat(output, is(singletonList("A")));
    }

    @Ignore("Remove to run test")
    @Test
    public void testTwoByTwoDiamond() {
        List<String> output = diamondPrinter.printToList('B');
        assertThat(output, is(asList(" A ",
                                     "B B",
                                     " A ")));
    }

    @Ignore("Remove to run test")
    @Test
    public void testThreeByThreeDiamond() {
        List<String> output = diamondPrinter.printToList('C');
        assertThat(output, is(asList("  A  ",
                                     " B B ",
                                     "C   C",
                                     " B B ",
                                     "  A  ")));
    }

    @Ignore("Remove to run test")
    @Test
    public void testFourByFourDiamond() {
        List<String> output = diamondPrinter.printToList('D');
        assertThat(output, is(asList("   A   ",
                                     "  B B  ",
                                     " C   C ",
                                     "D     D",
                                     " C   C ",
                                     "  B B  ",
                                     "   A   ")));
    }

    @Ignore("Remove to run test")
    @Test
    public void testFullDiamond() {
        List<String> output = diamondPrinter.printToList('Z');
        assertThat(output, is(asList("                         A                         ",
                                     "                        B B                        ",
                                     "                       C   C                       ",
                                     "                      D     D                      ",
                                     "                     E       E                     ",
                                     "                    F         F                    ",
                                     "                   G           G                   ",
                                     "                  H             H                  ",
                                     "                 I               I                 ",
                                     "                J                 J                ",
                                     "               K                   K               ",
                                     "              L                     L              ",
                                     "             M                       M             ",
                                     "            N                         N            ",
                                     "           O                           O           ",
                                     "          P                             P          ",
                                     "         Q                               Q         ",
                                     "        R                                 R        ",
                                     "       S                                   S       ",
                                     "      T                                     T      ",
                                     "     U                                       U     ",
                                     "    V                                         V    ",
                                     "   W                                           W   ",
                                     "  X                                             X  ",
                                     " Y                                               Y ",
                                     "Z                                                 Z",
                                     " Y                                               Y ",
                                     "  X                                             X  ",
                                     "   W                                           W   ",
                                     "    V                                         V    ",
                                     "     U                                       U     ",
                                     "      T                                     T      ",
                                     "       S                                   S       ",
                                     "        R                                 R        ",
                                     "         Q                               Q         ",
                                     "          P                             P          ",
                                     "           O                           O           ",
                                     "            N                         N            ",
                                     "             M                       M             ",
                                     "              L                     L              ",
                                     "               K                   K               ",
                                     "                J                 J                ",
                                     "                 I               I                 ",
                                     "                  H             H                  ",
                                     "                   G           G                   ",
                                     "                    F         F                    ",
                                     "                     E       E                     ",
                                     "                      D     D                      ",
                                     "                       C   C                       ",
                                     "                        B B                        ",
                                     "                         A                         ")));
    }

}
import java.util.ArrayList;
import java.util.List;

class DiamondPrinter {

    List<String> printToList(char a) {
        List<String> diamond = new ArrayList<>();
        StringBuilder top = new StringBuilder();
        char c = 'A';
        int charDiff = a - c;
        String innerSpace = "";

        while(c <= a){
            String outerspace = "";
            for(int x = charDiff; x > 0; x--){
                outerspace+=" ";
            }
            if(c == 'A'){
                diamond.add(outerspace + c + outerspace);

            } else {
                diamond.add(outerspace + c + innerSpace + c + outerspace);
                innerSpace+=" ";
            }
            c+=1;
            charDiff--;
            innerSpace+=" ";
        }

        int diamondsize = diamond.size() - 1;

        for(int x = 1; x <= diamondsize; x++){
            diamond.add(diamond.get(diamondsize- x));
        }

        return diamond;
    }


}

What can you learn from this solution?

A huge amount can be learned from reading other people’s code. This is why we wanted to give exercism users the option of making their solutions public.

Here are some questions to help you reflect on this solution and learn the most from it.

  • What compromises have been made?
  • Are there new concepts here that you could read more about to improve your understanding?