Data commit

Task/CSV-data-manipulation/Java/csv-data-manipulation-2.java

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+public class CSV {
+    public static void main(String[] args) throws IOException {
+        CSV csv = new CSV("data.csv");
+        csv.sumAllRows();
+        csv.write();
+    }
+
+    private final File file;
+    private List<List<String>> data;
+
+    public CSV(File file) throws IOException {
+        this.file = file;
+        open();
+    }
+
+    /* convenience constructor */
+    public CSV(String path) throws IOException {
+        this(new File(path));
+    }
+
+    public void sumAllRows() {
+        appendColumn("SUM");
+        int sum;
+        int length;
+        for (int index = 1; index < data.size(); index++) {
+            sum = sum(data.get(index));
+            length = data.get(index).size();
+            data.get(index).set(length - 1, String.valueOf(sum));
+        }
+    }
+
+    private int sum(List<String> row) {
+        int sum = 0;
+        for (int index = 0; index < row.size() - 1; index++)
+            sum += Integer.parseInt(row.get(index));
+        return sum;
+    }
+
+    private void appendColumn(String title) {
+        List<String> titles = data.get(0);
+        titles.add(title);
+        /* append an empty cell to each row */
+        for (int index = 1; index < data.size(); index++)
+            data.get(index).add("");
+    }
+
+    private void open() throws IOException {
+        try (BufferedReader reader = new BufferedReader(new FileReader(file))) {
+            data = new ArrayList<>();
+            String line;
+            while ((line = reader.readLine()) != null) {
+                /* using a limit of -1 will preserve trailing commas */
+                data.add(new ArrayList<>(List.of(line.split(",", -1))));
+            }
+        }
+    }
+
+    public void write() throws IOException {
+        try (FileWriter writer = new FileWriter(file)) {
+            String newline = System.lineSeparator();
+            for (List<String> row : data) {
+                writer.write(String.join(",", row));
+                writer.write(newline);
+            }
+            writer.flush();
+        }
+    }
+}