Improve null safety

initializr-generator-spring/src/main/java/io/spring/initializr/generator/spring/properties/AbstractApplicationPropertiesContributor.java

@@ -94,7 +94,10 @@ private void writeFile(SourceStructure sourceStructure, ProfileName profile, App
 			throws IOException {
 		Path output = resolveOutputFile(sourceStructure, profile);
 		if (!Files.exists(output)) {
-			Files.createDirectories(output.getParent());
+			Path parent = output.getParent();
+			if (parent != null) {
+				Files.createDirectories(parent);
+			}
 			Files.createFile(output);
 		}
 		try (PrintWriter writer = new PrintWriter(Files.newOutputStream(output, StandardOpenOption.APPEND), false,

initializr-generator/src/main/java/io/spring/initializr/generator/language/java/JavaSourceCodeWriter.java

@@ -107,7 +107,10 @@ public void writeTo(SourceStructure structure, JavaSourceCode sourceCode) throws
 
 	private void writeTo(SourceStructure structure, JavaCompilationUnit compilationUnit) throws IOException {
 		Path output = structure.createSourceFile(compilationUnit.getPackageName(), compilationUnit.getName());
-		Files.createDirectories(output.getParent());
+		Path parent = output.getParent();
+		if (parent != null) {
+			Files.createDirectories(parent);
+		}
 		try (IndentingWriter writer = this.indentingWriterFactory.createIndentingWriter("java",
 				Files.newBufferedWriter(output))) {
 			writer.println("package " + compilationUnit.getPackageName() + ";");

initializr-generator/src/main/java/io/spring/initializr/generator/language/kotlin/KotlinSourceCodeWriter.java

@@ -83,7 +83,10 @@ public void writeTo(SourceStructure structure, KotlinSourceCode sourceCode) thro
 
 	private void writeTo(SourceStructure structure, KotlinCompilationUnit compilationUnit) throws IOException {
 		Path output = structure.createSourceFile(compilationUnit.getPackageName(), compilationUnit.getName());
-		Files.createDirectories(output.getParent());
+		Path parent = output.getParent();
+		if (parent != null) {
+			Files.createDirectories(parent);
+		}
 		try (IndentingWriter writer = this.indentingWriterFactory.createIndentingWriter("kotlin",
 				Files.newBufferedWriter(output))) {
 			writer.println("package " + escapeKotlinKeywords(compilationUnit.getPackageName()));

initializr-generator/src/main/java/io/spring/initializr/generator/project/contributor/MultipleResourcesProjectContributor.java

@@ -66,7 +66,10 @@ public void contribute(Path projectRoot) throws IOException {
 				String filename = extractFileName(root.getURI(), resource.getURI());
 				Path output = projectRoot.resolve(filename);
 				if (!Files.exists(output)) {
-					Files.createDirectories(output.getParent());
+					Path parent = output.getParent();
+					if (parent != null) {
+						Files.createDirectories(parent);
+					}
 					Files.createFile(output);
 				}
 				FileCopyUtils.copy(resource.getInputStream(), Files.newOutputStream(output));

initializr-generator/src/main/java/io/spring/initializr/generator/project/contributor/SingleResourceProjectContributor.java

@@ -57,7 +57,10 @@ public SingleResourceProjectContributor(String relativePath, String resourcePatt
 	public void contribute(Path projectRoot) throws IOException {
 		Path output = projectRoot.resolve(this.relativePath);
 		if (!Files.exists(output)) {
-			Files.createDirectories(output.getParent());
+			Path parent = output.getParent();
+			if (parent != null) {
+				Files.createDirectories(parent);
+			}
 			Files.createFile(output);
 		}
 		Resource resource = this.resolver.getResource(this.resourcePattern);

initializr-metadata/src/main/java/io/spring/initializr/metadata/Repository.java

@@ -84,7 +84,7 @@ public void setSnapshotsEnabled(boolean snapshotsEnabled) {
 	}
 
 	@Override
-	public boolean equals(Object obj) {
+	public boolean equals(@Nullable Object obj) {
 		if (this == obj) {
 			return true;
 		}