Refactor CSVExporter writer handling

xchart/src/main/java/org/knowm/xchart/CSVExporter.java

@@ -1,6 +1,11 @@
 package org.knowm.xchart;
 
-import java.io.*;
+import java.io.BufferedWriter;
+import java.io.File;
+import java.io.FileOutputStream;
+import java.io.OutputStreamWriter;
+import java.io.Writer;
+import java.nio.charset.StandardCharsets;
 
 /**
  * This class is used to export Chart data to a folder containing one or more CSV files. The parent
@@ -9,6 +14,8 @@
  */
 public class CSVExporter {
 
+  private static final String LINE_SEPARATOR = System.lineSeparator();
+
   /**
    * Export all XYChart series as rows in separate CSV files.
    *
@@ -31,29 +38,20 @@ public static void writeCSVRows(XYChart chart, String path2Dir) {
   public static void writeCSVRows(XYSeries series, String path2Dir) {
 
     File newFile = new File(path2Dir + series.getName() + ".csv");
-    Writer out = null;
-    try {
+    try (Writer out =
+        new BufferedWriter(
+            new OutputStreamWriter(new FileOutputStream(newFile), StandardCharsets.UTF_8))) {
 
-      out = new BufferedWriter(new OutputStreamWriter(new FileOutputStream(newFile), "UTF8"));
-      String csv = join(series.getXData(), ",") + System.getProperty("line.separator");
+      String csv = join(series.getXData(), ",") + LINE_SEPARATOR;
       out.write(csv);
-      csv = join(series.getYData(), ",") + System.getProperty("line.separator");
+      csv = join(series.getYData(), ",") + LINE_SEPARATOR;
       out.write(csv);
       if (series.getExtraValues() != null) {
-        csv = join(series.getExtraValues(), ",") + System.getProperty("line.separator");
+        csv = join(series.getExtraValues(), ",") + LINE_SEPARATOR;
         out.write(csv);
       }
     } catch (Exception e) {
       e.printStackTrace();
-    } finally {
-      if (out != null) {
-        try {
-          out.flush();
-          out.close();
-        } catch (IOException e) {
-          // NOP
-        }
-      }
     }
   }
 
@@ -102,10 +100,10 @@ public static void writeCSVColumns(XYChart chart, String path2Dir) {
   public static void writeCSVColumns(XYSeries series, String path2Dir) {
 
     File newFile = new File(path2Dir + series.getName() + ".csv");
-    Writer out = null;
-    try {
+    try (Writer out =
+        new BufferedWriter(
+            new OutputStreamWriter(new FileOutputStream(newFile), StandardCharsets.UTF_8))) {
 
-      out = new BufferedWriter(new OutputStreamWriter(new FileOutputStream(newFile), "UTF8"));
       double[] xData = series.getXData();
       double[] yData = series.getYData();
       double[] errorBarData = series.getExtraValues();
@@ -118,24 +116,12 @@ public static void writeCSVColumns(XYSeries series, String path2Dir) {
           sb.append(errorBarData[i]).append(",");
         }
         sb.setLength(sb.length() - 1);
-        sb.append(System.getProperty("line.separator"));
+        sb.append(LINE_SEPARATOR);
 
-        // String csv = xDataPoint + "," + yDataPoint + errorBarValue == null ? "" : ("," +
-        // errorBarValue) + System.getProperty("line.separator");
-        // String csv = + yDataPoint + System.getProperty("line.separator");
         out.write(sb.toString());
       }
     } catch (Exception e) {
       e.printStackTrace();
-    } finally {
-      if (out != null) {
-        try {
-          out.flush();
-          out.close();
-        } catch (IOException e) {
-          // NOP
-        }
-      }
     }
   }
 }

xchart/src/test/java/org/knowm/xchart/CSVExporterTest.java

@@ -0,0 +1,51 @@
+package org.knowm.xchart;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import java.io.File;
+import java.nio.charset.StandardCharsets;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.io.TempDir;
+
+public class CSVExporterTest {
+
+  @TempDir Path tempDir;
+
+  @Test
+  public void writeCSVRowsExportsXAndYDataRows() throws Exception {
+
+    XYChart chart = new XYChartBuilder().width(600).height(400).build();
+    chart.addSeries("series1", new double[] {1.0, 2.0, 3.0}, new double[] {12.0, 34.0, 56.0});
+
+    CSVExporter.writeCSVRows(chart.getSeries("series1"), tempDir.toString() + File.separator);
+
+    String csv = Files.readString(tempDir.resolve("series1.csv"), StandardCharsets.UTF_8);
+    assertThat(csv)
+        .isEqualTo(
+            "1.0,2.0,3.0"
+                + System.lineSeparator()
+                + "12.0,34.0,56.0"
+                + System.lineSeparator());
+  }
+
+  @Test
+  public void writeCSVColumnsExportsXAndYDataColumns() throws Exception {
+
+    XYChart chart = new XYChartBuilder().width(600).height(400).build();
+    chart.addSeries("series1", new double[] {1.0, 2.0, 3.0}, new double[] {12.0, 34.0, 56.0});
+
+    CSVExporter.writeCSVColumns(chart.getSeries("series1"), tempDir.toString() + File.separator);
+
+    String csv = Files.readString(tempDir.resolve("series1.csv"), StandardCharsets.UTF_8);
+    assertThat(csv)
+        .isEqualTo(
+            "1.0,12.0"
+                + System.lineSeparator()
+                + "2.0,34.0"
+                + System.lineSeparator()
+                + "3.0,56.0"
+                + System.lineSeparator());
+  }
+}