feat(io): add StudentCsvWriter

- add CSV writer for individual students - support sequential writing of student lists - preserve existing CSV data and avoid duplicate headers - reject missing files with IOException
2026-08-31 22:17:51 +04:00
parent 26f124bd0f
commit 4dadefd87f
1 changed files with 88 additions and 0 deletions
@@ -0,0 +1,88 @@
+package ru.project.io;
+
+import java.io.BufferedWriter;
+import java.io.File;
+import java.io.FileOutputStream;
+import java.io.IOException;
+import java.io.OutputStreamWriter;
+import java.nio.charset.StandardCharsets;
+import org.apache.commons.csv.CSVFormat;
+import org.apache.commons.csv.CSVPrinter;
+import ru.project.collection.MyList;
+import ru.project.student.Student;
+
+public class StudentCsvWriter {
+
+  private static final String GROUP_NUMBER_HEADER = "groupNumber";
+  private static final String AVERAGE_GRADE_HEADER = "averageGrade";
+  private static final String RECORD_BOOK_NUMBER_HEADER = "recordBookNumber";
+
+  private final String absoluteFilePath;
+
+  public StudentCsvWriter(String absoluteFilePath) {
+    this.absoluteFilePath = absoluteFilePath;
+  }
+
+  public void write(Student student) throws IOException {
+    ensureFileExists();
+
+    boolean fileIsEmpty = isFileEmpty();
+
+    try (CSVPrinter printer = createPrinter()) {
+      if (fileIsEmpty) {
+        writeHeader(printer);
+      }
+
+      writeStudent(printer, student);
+    }
+  }
+
+  public void write(MyList<Student>[] students) throws IOException {
+    ensureFileExists();
+
+    boolean fileIsEmpty = isFileEmpty();
+
+    try (CSVPrinter printer = createPrinter()) {
+      if (fileIsEmpty) {
+        writeHeader(printer);
+      }
+
+      for (MyList<Student> studentList : students) {
+        for (int i = 0; i < studentList.size(); i++) {
+          writeStudent(printer, studentList.get(i));
+        }
+      }
+    }
+  }
+
+  private CSVPrinter createPrinter() throws IOException {
+    BufferedWriter writer =
+        new BufferedWriter(
+            new OutputStreamWriter(
+                new FileOutputStream(absoluteFilePath, true), StandardCharsets.UTF_8));
+
+    return new CSVPrinter(writer, CSVFormat.DEFAULT);
+  }
+
+  private void writeHeader(CSVPrinter printer) throws IOException {
+    printer.printRecord(GROUP_NUMBER_HEADER, AVERAGE_GRADE_HEADER, RECORD_BOOK_NUMBER_HEADER);
+  }
+
+  private void writeStudent(CSVPrinter printer, Student student) throws IOException {
+
+    printer.printRecord(
+        student.getGroupNumber(), student.getAverageGrade(), student.getRecordBookNumber());
+  }
+
+  private void ensureFileExists() throws IOException {
+    File file = new File(absoluteFilePath);
+
+    if (!file.isFile()) {
+      throw new IOException("CSV file does not exist: " + absoluteFilePath);
+    }
+  }
+
+  private boolean isFileEmpty() {
+    return new File(absoluteFilePath).length() == 0;
+  }
+}