public static String getFilename(String path) {
        if (path == null) {
            return null;
        }
        
        int separatorIndex = path.lastIndexOf(FOLDER_SEPARATOR);
        return (separatorIndex != -1 ? path.substring(separatorIndex + 1) : path);
    }
@Test
    void testGetFilename() {
        // Test case 1: null path
        String path1 = null;
        String result1 = StringUtils.getFilename(path1);
        assertNull(result1);
        
        // Test case 2: path without separator
        String path2 = "myFile.txt";
        String expectedResult2 = "myFile.txt";
        String result2 = StringUtils.getFilename(path2);
        assertEquals(expectedResult2, result2);
        
        // Test case 3: path with separator
        String path3 = "myPath/myFile.txt";
        String expectedResult3 = "myFile.txt";
        String result3 = StringUtils.getFilename(path3);
        assertEquals(expectedResult3, result3);
        
        // Test case 4: path with multiple separators
        String path4 = "myPath/subPath/myFile.txt";
        String expectedResult4 = "myFile.txt";
        String result4 = StringUtils.getFilename(path4);
        assertEquals(expectedResult4, result4);
    }