Add CSVPrinter.printRecord[s](Stream).

src/changes/changes.xml

@@ -50,6 +50,7 @@
       <action issue="CSV-291" type="add" dev="ggregory" due-to="Gary Gregory">Make CSVRecord#values() public.</action>
       <action issue="CSV-264" type="add" dev="ggregory" due-to="Sagar Tiwari, Seth Falco, Alex Herbert, Gary Gregory">Add DuplicateHeaderMode for flexibility with header strictness. #114.</action>
       <action issue="CSV-295" type="add" dev="ggregory" due-to="Gary Gregory">Support for parallelism in CSVPrinter.</action>
+      <action issue="CSV-295" type="add" dev="ggregory" due-to="Gary Gregory">Add CSVPrinter.printRecord[s](Stream).</action>
       <action type="add" dev="ggregory">Add github/codeql-action.</action>
       <!-- UPDATE -->
       <action                 type="update" dev="kinow" due-to="Dependabot, Gary Gregory">Bump actions/cache from 2.1.6 to 3.0.6 #196, #233, #243.</action>

src/main/java/org/apache/commons/csv/CSVPrinter.java

@@ -29,6 +29,7 @@ import java.sql.ResultSet;
 import java.sql.SQLException;
 import java.util.Arrays;
 import java.util.Objects;
+import java.util.stream.Stream;
 
 /**
  * Prints values in a {@link CSVFormat CSV format}.
@@ -69,8 +70,21 @@ import java.util.Objects;
  */
 public final class CSVPrinter implements Flushable, Closeable {
 
+    /**
+     * Throws the given throwable.
+     *
+     * @param <T> The throwable cast type.
+     * @param throwable The throwable to rethrow.
+     * @return nothing because we throw.
+     * @throws T Always thrown.
+     */
+    @SuppressWarnings("unchecked")
+    private static <T extends Throwable> RuntimeException rethrow(final Throwable throwable) throws T {
+        throw (T) throwable;
+    }
     /** The place that the values get written. */
     private final Appendable appendable;
+
     private final CSVFormat format;
 
     /** True if we just began a new record. */
@@ -242,7 +256,7 @@ public final class CSVPrinter implements Flushable, Closeable {
     }
 
     /**
-     * Prints the given values a single record of delimiter separated values followed by the record separator.
+     * Prints the given values as a single record of delimiter separated values followed by the record separator.
      *
      * <p>
      * The values will be quoted if needed. Quotes and newLine characters will be escaped. This method adds the record
@@ -262,7 +276,7 @@ public final class CSVPrinter implements Flushable, Closeable {
     }
 
     /**
-     * Prints the given values a single record of delimiter separated values followed by the record separator.
+     * Prints the given values as a single record of delimiter separated values followed by the record separator.
      *
      * <p>
      * The values will be quoted if needed. Quotes and newLine characters will be escaped. This method adds the record
@@ -279,11 +293,46 @@ public final class CSVPrinter implements Flushable, Closeable {
     }
 
     /**
-     * Prints all the objects in the given collection handling nested collections/arrays as records.
+     * Prints the given values as a single record of delimiter separated values followed by the record separator.
      *
      * <p>
-     * If the given collection only contains simple objects, this method will print a single record like
+     * The values will be quoted if needed. Quotes and newLine characters will be escaped. This method adds the record
-     * {@link #printRecord(Iterable)}. If the given collections contains nested collections/arrays those nested elements
+     * separator to the output after printing the record, so there is no need to call {@link #println()}.
+     * </p>
+     *
+     * @param values
+     *            values to output.
+     * @throws IOException
+     *             If an I/O error occurs
+     * @since 1.10.0
+     */
+    public synchronized void printRecord(final Stream<?> values) throws IOException {
+        values.forEachOrdered(t -> {
+            try {
+                print(t);
+            } catch (IOException e) {
+                throw rethrow(e);
+            }
+        });
+        println();
+    }
+
+    private void printRecordObject(final Object value) throws IOException {
+        if (value instanceof Object[]) {
+            this.printRecord((Object[]) value);
+        } else if (value instanceof Iterable) {
+            this.printRecord((Iterable<?>) value);
+        } else {
+            this.printRecord(value);
+        }
+    }
+
+    /**
+     * Prints all the objects in the given {@link Iterable} handling nested collections/arrays as records.
+     *
+     * <p>
+     * If the given Iterable only contains simple objects, this method will print a single record like
+     * {@link #printRecord(Iterable)}. If the given Iterable contains nested collections/arrays those nested elements
      * will each be printed as records using {@link #printRecord(Object...)}.
      * </p>
      *
@@ -293,7 +342,7 @@ public final class CSVPrinter implements Flushable, Closeable {
      *
      * <pre>
      * <code>
-     * List&lt;String[]&gt; data = ...
+     * List&lt;String[]&gt; data = new ArrayList&lt;&gt;();
      * data.add(new String[]{ "A", "B", "C" });
      * data.add(new String[]{ "1", "2", "3" });
      * data.add(new String[]{ "A1", "B2", "C3" });
@@ -319,13 +368,7 @@ public final class CSVPrinter implements Flushable, Closeable {
      */
     public void printRecords(final Iterable<?> values) throws IOException {
         for (final Object value : values) {
-            if (value instanceof Object[]) {
+            printRecordObject(value);
-                this.printRecord((Object[]) value);
-            } else if (value instanceof Iterable) {
-                this.printRecord((Iterable<?>) value);
-            } else {
-                this.printRecord(value);
-            }
         }
     }
 
@@ -409,4 +452,56 @@ public final class CSVPrinter implements Flushable, Closeable {
         }
         printRecords(resultSet);
     }
+
+    /**
+     * Prints all the objects in the given {@link Stream} handling nested collections/arrays as records.
+     *
+     * <p>
+     * If the given Stream only contains simple objects, this method will print a single record like
+     * {@link #printRecord(Iterable)}. If the given Stream contains nested collections/arrays those nested elements
+     * will each be printed as records using {@link #printRecord(Object...)}.
+     * </p>
+     *
+     * <p>
+     * Given the following data structure:
+     * </p>
+     *
+     * <pre>
+     * <code>
+     * List&lt;String[]&gt; data = new ArrayList&lt;&gt;();
+     * data.add(new String[]{ "A", "B", "C" });
+     * data.add(new String[]{ "1", "2", "3" });
+     * data.add(new String[]{ "A1", "B2", "C3" });
+     * Stream&lt;String[]&gt; stream = data.stream();
+     * </code>
+     * </pre>
+     *
+     * <p>
+     * Calling this method will print:
+     * </p>
+     *
+     * <pre>
+     * <code>
+     * A, B, C
+     * 1, 2, 3
+     * A1, B2, C3
+     * </code>
+     * </pre>
+     *
+     * @param values
+     *            the values to print.
+     * @throws IOException
+     *             If an I/O error occurs
+     * @since 1.10.0
+     */
+    @SuppressWarnings("unused") // rethrow() throws IOException
+    public void printRecords(final Stream<?> values) throws IOException {
+        values.forEachOrdered(t -> {
+            try {
+                printRecordObject(t);
+            } catch (IOException e) {
+                throw rethrow(e);
+            }
+        });
+    }
 }

src/test/java/org/apache/commons/csv/CSVPrinterTest.java

@@ -56,6 +56,7 @@ import java.util.List;
 import java.util.Objects;
 import java.util.Random;
 import java.util.Vector;
+import java.util.stream.Stream;
 
 import org.apache.commons.io.FileUtils;
 import org.apache.commons.io.output.NullOutputStream;
@@ -588,6 +589,15 @@ public class CSVPrinterTest {
         }
     }
 
+    @Test
+    public void testExcelPrintAllStreamOfArrays() throws IOException {
+        final StringWriter sw = new StringWriter();
+        try (final CSVPrinter printer = new CSVPrinter(sw, CSVFormat.EXCEL)) {
+            printer.printRecords(Stream.of(new String[][] { { "r1c1", "r1c2" }, { "r2c1", "r2c2" } }));
+            assertEquals("r1c1,r1c2" + recordSeparator + "r2c1,r2c2" + recordSeparator, sw.toString());
+        }
+    }
+
     @Test
     public void testExcelPrinter1() throws IOException {
         final StringWriter sw = new StringWriter();
@@ -1456,6 +1466,28 @@ public class CSVPrinterTest {
         assertEquals(content, sw.toString());
     }
 
+    @Test
+    public void testPrintRecordStream() throws IOException {
+        final String code = "a1,b1\n" // 1)
+            + "a2,b2\n" // 2)
+            + "a3,b3\n" // 3)
+            + "a4,b4\n"// 4)
+        ;
+        final String[][] res = {{"a1", "b1"}, {"a2", "b2"}, {"a3", "b3"}, {"a4", "b4"}};
+        final CSVFormat format = CSVFormat.DEFAULT;
+        final StringWriter sw = new StringWriter();
+        try (final CSVPrinter printer = format.print(sw); final CSVParser parser = CSVParser.parse(code, format)) {
+            for (final CSVRecord record : parser) {
+                printer.printRecord(record.stream());
+            }
+        }
+        try (final CSVParser parser = CSVParser.parse(sw.toString(), format)) {
+            final List<CSVRecord> records = parser.getRecords();
+            assertFalse(records.isEmpty());
+            Utils.compare("Fail", res, records);
+        }
+    }
+
     @Test
     public void testPrintRecordsWithCSVRecord() throws IOException {
         final String[] values = {"A", "B", "C"};