Fixed a bug in the creation of the result due to missing slashes.

core/src/main/java/de/jplag/reporting/FilePathUtil.java

@@ -26,4 +26,23 @@ public static String getRelativeSubmissionPath(File file, Submission submission,
         return Path.of(submissionToIdFunction.apply(submission), submission.getRoot().toPath().relativize(file.toPath()).toString()).toString();
     }
 
+    /**
+     * Joins logical paths using a slash. This method ensures, that no duplicate slashes are created in between.
+     * @param left The left path segment
+     * @param right The right path segment
+     * @return The joined paths
+     */
+    public static String joinPathSegments(String left, String right) {
+        String rightStripped = right;
+        while (rightStripped.startsWith("/")) {
+            rightStripped = rightStripped.substring(1);
+        }
+
+        String leftStripped = left;
+        while (leftStripped.endsWith("/")) {
+            leftStripped = leftStripped.substring(0, leftStripped.length() - 1);
+        }
+
+        return leftStripped + "/" + rightStripped;
+    }
 }

core/src/main/java/de/jplag/reporting/reportobject/ReportObjectFactory.java

@@ -112,7 +112,7 @@ private void copySubmissionFilesToReport(JPlagResult result) {
                 if (relativeFilePath.isEmpty()) {
                     relativeFilePath = file.getName();
                 }
-                String zipPath = submissionRootPath + relativeFilePath;
+                String zipPath = FilePathUtil.joinPathSegments(submissionRootPath, relativeFilePath);
 
                 File fileToCopy = getFileToCopy(language, file);
                 this.resultWriter.addFileContentEntry(zipPath, fileToCopy);

core/src/test/java/de/jplag/reporting/FilePathUtilTest.java

@@ -0,0 +1,26 @@
+package de.jplag.reporting;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+import org.junit.jupiter.api.Test;
+
+class FilePathUtilTest {
+    private static final String JOINED = "left/right";
+    private static final String LEFT = "left";
+    private static final String RIGHT = "right";
+
+    @Test
+    void testJoinPath() {
+        assertEquals(JOINED, FilePathUtil.joinPathSegments(LEFT, RIGHT));
+    }
+
+    @Test
+    void testJoinPathWithLeftSlashSuffix() {
+        assertEquals(JOINED, FilePathUtil.joinPathSegments(LEFT + "/", RIGHT));
+    }
+
+    @Test
+    void testJoinPathWithRightSlashSuffix() {
+        assertEquals(JOINED, FilePathUtil.joinPathSegments(LEFT, "/" + RIGHT));
+    }
+}