Use java.nio to load filter files (spotbugs#2684)

* test: load a filter with non-ascii characters in file name

* Use java.nio to load filter files

java.io.FileInputStream seems to be running into issues when trying to
load files with non-ascii charatecter in the file name.
Other similar issues point to this happening on a Mac, so it might be
dependent on the combination of OS/JDK version/user settings
Originally reported here:
JetBrains/spotbugs-intellij-plugin#1492

CHANGELOG.md

@@ -9,6 +9,7 @@ Currently the versioning policy of this project follows [Semantic Versioning v2.
 
 ### Fixed
 - Fixed false positive UPM_UNCALLED_PRIVATE_METHOD for method used in JUnit's MethodSource ([[#2379](https://github.com/spotbugs/spotbugs/issues/2379)])
+- Use java.nio to load filter files ([[#2684](https://github.com/spotbugs/spotbugs/pull/2684)])
 
 - tbd
 

spotbugs-tests/src/test/java/edu/umd/cs/findbugs/filter/Utf8FilterFileNameTest.java

@@ -0,0 +1,52 @@
+/*
+ * Contributions to SpotBugs
+ * Copyright (C) 2023, the SpotBugs authors
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ */
+package edu.umd.cs.findbugs.filter;
+
+import static org.junit.jupiter.api.Assertions.fail;
+
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Path;
+
+
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.io.TempDir;
+
+
+/**
+ * @author gtoison
+ */
+class Utf8FilterFileNameTest {
+    @TempDir
+    private Path folderPath;
+
+    @Test
+    void loadFilter() {
+        Path filterPath = folderPath.resolve("äéàùçæð.xml");
+
+        try {
+            Files.createFile(filterPath);
+            Files.writeString(filterPath, "<FindBugsFilter/>");
+
+            Filter filter = new Filter(filterPath.toAbsolutePath().toString());
+        } catch (IOException e) {
+            fail("Error loading filter file " + filterPath, e);
+        }
+    }
+}

spotbugs/src/main/java/edu/umd/cs/findbugs/filter/Filter.java

@@ -20,11 +20,13 @@
 package edu.umd.cs.findbugs.filter;
 
 import java.io.File;
-import java.io.FileInputStream;
 import java.io.IOException;
 import java.io.InputStream;
 import java.io.OutputStream;
 import java.io.Reader;
+import java.nio.file.FileSystems;
+import java.nio.file.Files;
+import java.nio.file.Path;
 import java.util.IdentityHashMap;
 import java.util.Iterator;
 
@@ -204,7 +206,8 @@ public boolean match(BugInstance bugInstance) {
      * @throws ParserConfigurationException
      */
     private void parse(String fileName) throws IOException, SAXException, ParserConfigurationException {
-        FileInputStream fileInputStream = new FileInputStream(new File(fileName));
+        Path path = FileSystems.getDefault().getPath(fileName);
+        InputStream fileInputStream = Files.newInputStream(path);
         parse(fileName, fileInputStream);
     }