Do some refactoring and reformatting. Also, use logback instead of plain ol' System.out.println().

pom.xml

@@ -14,7 +14,9 @@
 	<version>0.0.2-SNAPSHOT</version>
 
 	<properties>
+		<logback.version>1.2.10</logback.version>
 		<pdfbox.version>2.0.25</pdfbox.version>
+		<slf4j.version>1.7.35</slf4j.version>
 	</properties>
 
 	<dependencies>
@@ -35,10 +37,19 @@
 			<artifactId>pdfbox</artifactId>
 			<version>${pdfbox.version}</version>
 		</dependency>
+		<dependency>
+			<groupId>org.slf4j</groupId>
+			<artifactId>slf4j-api</artifactId>
+			<version>${slf4j.version}</version>
+		</dependency>
+		<dependency>
+			<groupId>ch.qos.logback</groupId>
+			<artifactId>logback-classic</artifactId>
+			<version>${logback.version}</version>
+		</dependency>
 		<dependency>
 			<groupId>org.junit.jupiter</groupId>
 			<artifactId>junit-jupiter-api</artifactId>
-			<scope>test</scope>
 		</dependency>
 	</dependencies>
 	<build>

src/main/java/ch/fritteli/labyrinth/generator/Main.java

@@ -7,10 +7,12 @@ import ch.fritteli.labyrinth.generator.renderer.pdffile.PDFFileRenderer;
 import ch.fritteli.labyrinth.generator.renderer.text.TextRenderer;
 import ch.fritteli.labyrinth.generator.renderer.textfile.TextFileRenderer;
 import lombok.NonNull;
+import lombok.extern.slf4j.Slf4j;
 
 import java.nio.file.Path;
 import java.nio.file.Paths;
 
+@Slf4j
 public class Main {
     public static void main(@NonNull final String[] args) {
         int width = 100;
@@ -28,19 +30,19 @@ public class Main {
         final PDFFileRenderer pdfFileRenderer = PDFFileRenderer.newInstance()
                 .setTargetFile(userHome.resolve(baseFilename + ".pdf"));
 
-        System.out.println("Labyrinth-ID: " + labyrinth.getRandomSeed());
+        log.info("Labyrinth-ID: {}", labyrinth.getRandomSeed());
         // Render Labyrinth to stdout
-        System.out.println(textRenderer.render(labyrinth));
+        log.info("Text rendering:\n{}", textRenderer.render(labyrinth));
         // Render Labyrinth solution to stdout
-        System.out.println(textRenderer.setRenderSolution(true).render(labyrinth));
+        log.info("Text rendering with solution:\n{}", textRenderer.setRenderSolution(true).render(labyrinth));
         // Render HTML to stdout
-        System.out.println(htmlRenderer.render(labyrinth));
+        log.info("HTML rendering:\n{}", htmlRenderer.render(labyrinth));
         // Render Labyrinth and solution to (separate) files
-        System.out.println(textFileRenderer.render(labyrinth));
+        log.info("Text rendering to file:\n{}", textFileRenderer.render(labyrinth));
         // Render HTML to file
-        System.out.println(htmlFileRenderer.render(labyrinth));
+        log.info("HTML rendering to file:\n{}", htmlFileRenderer.render(labyrinth));
         // Render PDF to file
-        System.out.println(pdfFileRenderer.render(labyrinth));
+        log.info("PDF rendering to file:\n{}", pdfFileRenderer.render(labyrinth));
     }
 
     private static String getBaseFilename(@NonNull final Labyrinth labyrinth) {

src/main/java/ch/fritteli/labyrinth/generator/renderer/html/HTMLRenderer.java

@@ -16,6 +16,7 @@ public class HTMLRenderer implements Renderer<String> {
     }
 
     @NonNull
+    @Override
     public String render(@NonNull final Labyrinth labyrinth) {
         if (labyrinth.getWidth() == 0 || labyrinth.getHeight() == 0) {
             return this.getPreamble(labyrinth) + POSTAMBLE;

src/main/java/ch/fritteli/labyrinth/generator/renderer/htmlfile/HTMLFileRenderer.java

@@ -3,25 +3,30 @@ package ch.fritteli.labyrinth.generator.renderer.htmlfile;
 import ch.fritteli.labyrinth.generator.model.Labyrinth;
 import ch.fritteli.labyrinth.generator.renderer.Renderer;
 import ch.fritteli.labyrinth.generator.renderer.html.HTMLRenderer;
+import io.vavr.control.Option;
+import io.vavr.control.Try;
 import lombok.NonNull;
+import lombok.extern.slf4j.Slf4j;
 
+import java.io.File;
 import java.io.IOException;
 import java.nio.charset.StandardCharsets;
 import java.nio.file.Files;
 import java.nio.file.Path;
+import java.util.NoSuchElementException;
 
+@Slf4j
 public class HTMLFileRenderer implements Renderer<Path> {
     @NonNull
     private static final HTMLRenderer HTML_RENDERER = HTMLRenderer.newInstance();
-    private Path targetFile;
+    @NonNull
+    private Option<Path> targetFile;
 
     private HTMLFileRenderer() {
-        try {
+        this.targetFile = Try
-            this.targetFile = Files.createTempFile("labyrinth_", ".html");
+                .of(() -> Files.createTempFile("labyrinth_", ".html"))
-        } catch (IOException e) {
+                .onFailure(ex -> log.error("Unable to set default target file.", ex))
-            System.err.println("Unable to set default target file.");
+                .toOption();
-            e.printStackTrace();
-        }
     }
 
     @NonNull
@@ -30,30 +35,33 @@ public class HTMLFileRenderer implements Renderer<Path> {
     }
 
     public boolean isTargetFileDefinedAndWritable() {
-        return this.targetFile != null && this.targetFile.toFile().canWrite();
+        return this.targetFile
+                .map(Path::toFile)
+                .exists(File::canWrite);
     }
 
     @NonNull
     public HTMLFileRenderer setTargetFile(@NonNull final Path targetFile) {
-        this.targetFile = targetFile;
+        this.targetFile = Option.of(targetFile);
         return this;
     }
 
+    @NonNull
     @Override
     public Path render(@NonNull final Labyrinth labyrinth) {
         if (!this.isTargetFileDefinedAndWritable()) {
             try {
-                Files.createFile(this.targetFile);
+                Files.createFile(this.targetFile.get());
-            } catch (IOException e) {
+            } catch (IOException | NoSuchElementException e) {
                 throw new IllegalArgumentException("Cannot write to target file.", e);
             }
         }
         final String html = HTML_RENDERER.render(labyrinth);
+        final Path targetFile = this.targetFile.get();
         try {
-            Files.writeString(this.targetFile, html, StandardCharsets.UTF_8);
+            Files.writeString(targetFile, html, StandardCharsets.UTF_8);
         } catch (IOException e) {
-            System.err.println("Failed writing to file " + this.targetFile.normalize().toString());
+            log.error("Failed writing to file " + targetFile.normalize(), e);
-            e.printStackTrace();
         }
         return targetFile;
     }

src/main/java/ch/fritteli/labyrinth/generator/renderer/pdf/Generator.java

@@ -8,6 +8,7 @@ import io.vavr.control.Option;
 import lombok.NonNull;
 import lombok.RequiredArgsConstructor;
 import lombok.Value;
+import lombok.extern.slf4j.Slf4j;
 import org.apache.pdfbox.pdmodel.PDDocument;
 import org.apache.pdfbox.pdmodel.PDDocumentInformation;
 import org.apache.pdfbox.pdmodel.PDPage;
@@ -20,14 +21,12 @@ import java.io.ByteArrayOutputStream;
 import java.io.IOException;
 
 @RequiredArgsConstructor
+@Slf4j
 class Generator {
     @NonNull
     private final Labyrinth labyrinth;
 
-    private static boolean isValid(@NonNull final Position position) {
+    @NonNull
-        return position.getX() >= 0 && position.getY() >= 0;
-    }
-
     public byte[] generate() {
         final float pageWidth = this.labyrinth.getWidth() * PDFRenderer.SCALE + 2 * PDFRenderer.MARGIN;
         final float pageHeight = this.labyrinth.getHeight() * PDFRenderer.SCALE + 2 * PDFRenderer.MARGIN;
@@ -48,14 +47,14 @@ class Generator {
             this.drawVerticalLines(puzzlePageContentStream, solutionPageContentStream);
             this.drawSolution(solutionPageContentStream);
         } catch (IOException e) {
-            e.printStackTrace();
+            log.error("Error while rendering PDF document", e);
         }
         final ByteArrayOutputStream output = new ByteArrayOutputStream();
         try {
             pdDocument.save(output);
             pdDocument.close();
         } catch (IOException e) {
-            e.printStackTrace();
+            log.error("Error while writing PDF data", e);
         }
         return output.toByteArray();
     }

src/main/java/ch/fritteli/labyrinth/generator/renderer/pdf/PDFRenderer.java

@@ -16,8 +16,8 @@ public class PDFRenderer implements Renderer<byte[]> {
         return new PDFRenderer();
     }
 
-    @Override
     @NonNull
+    @Override
     public byte[] render(@NonNull final Labyrinth labyrinth) {
         final Generator generator = new Generator(labyrinth);
         return generator.generate();

src/main/java/ch/fritteli/labyrinth/generator/renderer/pdffile/PDFFileRenderer.java

@@ -6,6 +6,7 @@ import ch.fritteli.labyrinth.generator.renderer.pdf.PDFRenderer;
 import io.vavr.control.Option;
 import io.vavr.control.Try;
 import lombok.NonNull;
+import lombok.extern.slf4j.Slf4j;
 
 import java.io.File;
 import java.io.IOException;
@@ -13,6 +14,7 @@ import java.nio.file.Files;
 import java.nio.file.Path;
 import java.util.NoSuchElementException;
 
+@Slf4j
 public class PDFFileRenderer implements Renderer<Path> {
     @NonNull
     private static final PDFRenderer PDF_RENDERER = PDFRenderer.newInstance();
@@ -22,10 +24,7 @@ public class PDFFileRenderer implements Renderer<Path> {
     private PDFFileRenderer() {
         this.targetFile = Try
                 .of(() -> Files.createTempFile("labyrinth_", ".pdf"))
-                .onFailure(ex -> {
+                .onFailure(ex -> log.error("Unable to set default target file.", ex))
-                    System.err.println("Unable to set default target file.");
-                    ex.printStackTrace();
-                })
                 .toOption();
     }
 
@@ -37,8 +36,7 @@ public class PDFFileRenderer implements Renderer<Path> {
     public boolean isTargetFileDefinedAndWritable() {
         return this.targetFile
                 .map(Path::toFile)
-                .map(File::canWrite)
+                .exists(File::canWrite);
-                .getOrElse(false);
     }
 
     @NonNull
@@ -47,6 +45,7 @@ public class PDFFileRenderer implements Renderer<Path> {
         return this;
     }
 
+    @NonNull
     @Override
     public Path render(@NonNull final Labyrinth labyrinth) {
         if (!this.isTargetFileDefinedAndWritable()) {
@@ -61,8 +60,7 @@ public class PDFFileRenderer implements Renderer<Path> {
         try {
             Files.write(targetFile, bytes);
         } catch (IOException e) {
-            System.err.println("Failed writing to file " + targetFile.normalize().toString());
+            log.error("Failed writing to file " + targetFile.normalize(), e);
-            e.printStackTrace();
         }
         return targetFile;
     }

src/main/java/ch/fritteli/labyrinth/generator/renderer/text/TextRenderer.java

@@ -23,6 +23,7 @@ public class TextRenderer implements Renderer<String> {
     }
 
     @NonNull
+    @Override
     public String render(@NonNull final Labyrinth labyrinth) {
         if (labyrinth.getWidth() == 0 || labyrinth.getHeight() == 0) {
             return "";

src/main/java/ch/fritteli/labyrinth/generator/renderer/textfile/TextFileRenderer.java

@@ -4,29 +4,42 @@ import ch.fritteli.labyrinth.generator.model.Labyrinth;
 import ch.fritteli.labyrinth.generator.renderer.Renderer;
 import ch.fritteli.labyrinth.generator.renderer.text.TextRenderer;
 import io.vavr.collection.List;
+import io.vavr.control.Option;
+import io.vavr.control.Try;
 import lombok.NonNull;
+import lombok.extern.slf4j.Slf4j;
 
+import java.io.File;
 import java.io.IOException;
 import java.nio.charset.StandardCharsets;
 import java.nio.file.Files;
 import java.nio.file.Path;
+import java.util.NoSuchElementException;
 
+@Slf4j
 public class TextFileRenderer implements Renderer<List<Path>> {
     @NonNull
     private static final TextRenderer TEXT_RENDERER = TextRenderer.newInstance();
-    private Path targetLabyrinthFile;
+    @NonNull
-    private Path targetSolutionFile;
+    private Option<Path> targetLabyrinthFile;
+    @NonNull
+    private Option<Path> targetSolutionFile;
 
     private TextFileRenderer() {
-        try {
+        this.targetLabyrinthFile = Try
-            this.targetLabyrinthFile = Files.createTempFile("labyrinth_", ".txt");
+                .of(() -> Files.createTempFile("labyrinth_", ".txt"))
-            this.targetSolutionFile = this.targetLabyrinthFile.getParent().resolve(
+                .onFailure(ex -> log.error("Unable to set default target file", ex))
-                    this.targetLabyrinthFile.getFileName().toString().replace(".txt", "-solution.txt")
+                .toOption();
-            );
+
-        } catch (IOException e) {
+        this.targetSolutionFile = this.targetLabyrinthFile.toTry()
-            System.err.println("Unable to set default target file.");
+                .map(Path::getParent)
-            e.printStackTrace();
+                .flatMap(parent -> this.targetLabyrinthFile.toTry()
-        }
+                        .map(Path::getFileName)
+                        .map(Path::toString)
+                        .map(a -> a.replace(".txt", "-solution.txt"))
+                        .map(parent::resolve))
+                .onFailure(ex -> log.error("Unable to set default solution target file", ex))
+                .toOption();
     }
 
     @NonNull
@@ -35,38 +48,44 @@ public class TextFileRenderer implements Renderer<List<Path>> {
     }
 
     public boolean isTargetLabyrinthFileDefinedAndWritable() {
-        return this.targetLabyrinthFile != null && this.targetLabyrinthFile.toFile().canWrite();
+        return this.targetLabyrinthFile
+                .map(Path::toFile)
+                .exists(File::canWrite);
     }
 
     public boolean isTargetSolutionFileDefinedAndWritable() {
-        return this.targetSolutionFile != null && this.targetSolutionFile.toFile().canWrite();
+        return this.targetSolutionFile
+                .map(Path::toFile)
+                .exists(File::canWrite);
     }
 
     @NonNull
     public TextFileRenderer setTargetLabyrinthFile(@NonNull final Path targetLabyrinthFile) {
-        this.targetLabyrinthFile = targetLabyrinthFile;
+        this.targetLabyrinthFile = Option.of(targetLabyrinthFile);
         return this;
     }
 
     @NonNull
     public TextFileRenderer setTargetSolutionFile(@NonNull final Path targetSolutionFile) {
-        this.targetSolutionFile = targetSolutionFile;
+        this.targetSolutionFile = Option.of(targetSolutionFile);
         return this;
     }
 
+    @NonNull
     @Override
     public List<Path> render(@NonNull final Labyrinth labyrinth) {
         if (!this.isTargetLabyrinthFileDefinedAndWritable()) {
             try {
-                Files.createFile(this.targetLabyrinthFile);
+                Files.createFile(this.targetLabyrinthFile.get());
-            } catch (IOException e) {
+            } catch (IOException | NoSuchElementException e) {
+                log.error("Cannot write to target labyrinth file.", e);
                 throw new IllegalArgumentException("Cannot write to target labyrinth file.", e);
             }
         }
         if (!this.isTargetSolutionFileDefinedAndWritable()) {
             try {
-                Files.createFile(this.targetSolutionFile);
+                Files.createFile(this.targetSolutionFile.get());
-            } catch (IOException e) {
+            } catch (IOException | NoSuchElementException e) {
                 throw new IllegalArgumentException("Cannot write to target solution file.", e);
             }
         }
@@ -76,13 +95,18 @@ public class TextFileRenderer implements Renderer<List<Path>> {
             text = TEXT_RENDERER.setRenderSolution(false).render(labyrinth).strip();
             solution = TEXT_RENDERER.setRenderSolution(true).render(labyrinth).strip();
         }
+        final Path targetLabyrinthFile = this.targetLabyrinthFile.get();
+        final Path targetSolutionFile = this.targetSolutionFile.get();
         try {
-            Files.write(this.targetLabyrinthFile, text.getBytes(StandardCharsets.UTF_8));
+            Files.write(targetLabyrinthFile, text.getBytes(StandardCharsets.UTF_8));
-            Files.write(this.targetSolutionFile, solution.getBytes(StandardCharsets.UTF_8));
         } catch (IOException e) {
-            System.err.println("Failed writing to file " + this.targetLabyrinthFile.normalize().toString());
+            log.error("Failed writing to file " + targetLabyrinthFile.normalize(), e);
-            e.printStackTrace();
         }
-        return List.of(this.targetLabyrinthFile, this.targetSolutionFile);
+        try {
+            Files.write(targetSolutionFile, solution.getBytes(StandardCharsets.UTF_8));
+        } catch (IOException e) {
+            log.error("Failed writing to file " + targetSolutionFile.normalize());
+        }
+        return List.of(targetLabyrinthFile, targetSolutionFile);
     }
 }

src/main/resources/logback.xml

@@ -0,0 +1,16 @@
+<?xml version="1.0" encoding="utf-8" ?>
+<configuration>
+    <shutdownHook class="ch.qos.logback.core.hook.DelayingShutdownHook"/>
+
+    <appender name="STDOUT" class="ch.qos.logback.core.ConsoleAppender">
+        <!-- encoders are by default assigned the type
+        ch.qos.logback.classic.encoder.PatternLayoutEncoder -->
+        <encoder>
+            <pattern>%d{HH:mm:ss.SSS} [%thread] %-5level %logger{36} - %msg%n</pattern>
+        </encoder>
+    </appender>
+
+    <root level="info">
+        <appender-ref ref="STDOUT"/>
+    </root>
+</configuration>