refactor: fix several issues reported by sonar

jadx-core/src/main/java/jadx/core/dex/info/ConstStorage.java

@@ -91,12 +91,7 @@ public class ConstStorage {
 	}
 
 	private ValueStorage getClsValues(ClassNode cls) {
-		ValueStorage classValues = classes.get(cls);
-		if (classValues == null) {
-			classValues = new ValueStorage();
-			classes.put(cls, classValues);
-		}
-		return classValues;
+		return classes.computeIfAbsent(cls, c -> new ValueStorage());
 	}
 
 	@Nullable

jadx-core/src/main/java/jadx/core/export/TemplateFile.java

@@ -16,8 +16,6 @@ import org.jetbrains.annotations.Nullable;
 
 import jadx.core.utils.exceptions.JadxRuntimeException;
 
-import static jadx.core.utils.files.FileUtils.close;
-
 /**
  * Simple template engine
  * Syntax for replace variable with value: '{{variable}}'
@@ -56,21 +54,15 @@ public class TemplateFile {
 	}
 
 	public String build() throws IOException {
-		ByteArrayOutputStream out = new ByteArrayOutputStream();
-		try {
+		try (ByteArrayOutputStream out = new ByteArrayOutputStream()) {
 			process(out);
-		} finally {
-			close(out);
+			return out.toString();
 		}
-		return out.toString();
 	}
 
 	public void save(File outFile) throws IOException {
-		OutputStream out = new FileOutputStream(outFile);
-		try {
+		try (OutputStream out = new FileOutputStream(outFile)) {
 			process(out);
-		} finally {
-			close(out);
 		}
 	}
 

jadx-core/src/main/java/jadx/core/utils/files/FileUtils.java

@@ -18,6 +18,7 @@ import java.util.List;
 import java.util.Objects;
 import java.util.jar.JarEntry;
 import java.util.jar.JarOutputStream;
+import java.util.stream.Stream;
 import java.util.zip.ZipEntry;
 import java.util.zip.ZipFile;
 
@@ -92,9 +93,8 @@ public class FileUtils {
 	}
 
 	public static void deleteDir(Path dir) {
-		try {
-			Files.walk(dir)
-					.sorted(Comparator.reverseOrder())
+		try (Stream<Path> pathStream = Files.walk(dir)) {
+			pathStream.sorted(Comparator.reverseOrder())
 					.map(Path::toFile)
 					.forEach(File::delete);
 		} catch (Exception e) {