8276970: Default charset for PrintWriter that wraps PrintStream

Reviewed-by: rriggs, alanb

Author: naotoj

src/java.base/share/classes/java/io/OutputStreamWriter.java

@@ -99,15 +99,17 @@ public OutputStreamWriter(OutputStream out, String charsetName)
     }
 
     /**
-     * Creates an OutputStreamWriter that uses the default character encoding.
+     * Creates an OutputStreamWriter that uses the default character encoding, or
+     * where {@code out} is a {@code PrintStream}, the charset used by the print
+     * stream.
      *
      * @param  out  An OutputStream
      * @see Charset#defaultCharset()
      */
     public OutputStreamWriter(OutputStream out) {
         super(out);
         se = StreamEncoder.forOutputStreamWriter(out, this,
-                Charset.defaultCharset());
+                out instanceof PrintStream ps ? ps.charset() : Charset.defaultCharset());
     }
 
     /**

src/java.base/share/classes/java/io/PrintStream.java

@@ -68,6 +68,7 @@ public class PrintStream extends FilterOutputStream
     private final boolean autoFlush;
     private boolean trouble = false;
     private Formatter formatter;
+    private final Charset charset;
 
     /**
      * Track both the text- and character-output streams, so that their buffers
@@ -108,7 +109,8 @@ private static Charset toCharset(String csn)
     private PrintStream(boolean autoFlush, OutputStream out) {
         super(out);
         this.autoFlush = autoFlush;
-        this.charOut = new OutputStreamWriter(this);
+        this.charset = out instanceof PrintStream ps ? ps.charset() : Charset.defaultCharset();
+        this.charOut = new OutputStreamWriter(this, charset);
         this.textOut = new BufferedWriter(charOut);
     }
 
@@ -124,7 +126,8 @@ private PrintStream(boolean autoFlush, Charset charset, OutputStream out) {
     /**
      * Creates a new print stream, without automatic line flushing, with the
      * specified OutputStream. Characters written to the stream are converted
-     * to bytes using the default charset.
+     * to bytes using the default charset, or where {@code out} is a
+     * {@code PrintStream}, the charset used by the print stream.
      *
      * @param  out        The output stream to which values and objects will be
      *                    printed
@@ -139,7 +142,8 @@ public PrintStream(OutputStream out) {
     /**
      * Creates a new print stream, with the specified OutputStream and line
      * flushing. Characters written to the stream are converted to bytes using
-     * the default charset.
+     * the default charset, or where {@code out} is a {@code PrintStream},
+     * the charset used by the print stream.
      *
      * @param  out        The output stream to which values and objects will be
      *                    printed
@@ -201,6 +205,7 @@ public PrintStream(OutputStream out, boolean autoFlush, Charset charset) {
         this.autoFlush = autoFlush;
         this.charOut = new OutputStreamWriter(this, charset);
         this.textOut = new BufferedWriter(charOut);
+        this.charset = charset;
     }
 
     /**
@@ -1374,4 +1379,12 @@ public PrintStream append(char c) {
         return this;
     }
 
+    /**
+     * {@return the charset used in this {@code PrintStream} instance}
+     *
+     * @since 18
+     */
+    public Charset charset() {
+        return charset;
+    }
 }

src/java.base/share/classes/java/io/PrintWriter.java

@@ -118,7 +118,8 @@ public PrintWriter(Writer out,
      * Creates a new PrintWriter, without automatic line flushing, from an
      * existing OutputStream.  This convenience constructor creates the
      * necessary intermediate OutputStreamWriter, which will convert characters
-     * into bytes using the default charset.
+     * into bytes using the default charset, or where {@code out} is a
+     * {@code PrintStream}, the charset used by the print stream.
      *
      * @param  out        An output stream
      *
@@ -132,8 +133,9 @@ public PrintWriter(OutputStream out) {
     /**
      * Creates a new PrintWriter from an existing OutputStream.  This
      * convenience constructor creates the necessary intermediate
-     * OutputStreamWriter, which will convert characters into bytes using the
-     * default charset.
+     * OutputStreamWriter, which will convert characters into bytes using
+     * the default charset, or where {@code out} is a {@code PrintStream},
+     * the charset used by the print stream.
      *
      * @param  out        An output stream
      * @param  autoFlush  A boolean; if true, the {@code println},
@@ -144,7 +146,7 @@ public PrintWriter(OutputStream out) {
      * @see Charset#defaultCharset()
      */
     public PrintWriter(OutputStream out, boolean autoFlush) {
-        this(out, autoFlush, Charset.defaultCharset());
+        this(out, autoFlush, out instanceof PrintStream ps ? ps.charset() : Charset.defaultCharset());
     }
 
     /**

test/jdk/java/io/PrintStream/InheritEncodingTest.java

@@ -0,0 +1,107 @@
+/*
+ * Copyright (c) 2021, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+import org.testng.annotations.DataProvider;
+import org.testng.annotations.Test;
+import static org.testng.Assert.assertEquals;
+
+import java.io.ByteArrayOutputStream;
+import java.io.IOException;
+import java.io.OutputStreamWriter;
+import java.io.PrintStream;
+import java.io.PrintWriter;
+import java.nio.charset.Charset;
+import java.nio.charset.StandardCharsets;
+
+/**
+ * @test
+ * @bug 8276970
+ * @summary Test to verify the charset in PrintStream is inherited
+ *      in the OutputStreamWriter/PrintWriter
+ * @run testng InheritEncodingTest
+ */
+@Test
+public class InheritEncodingTest {
+
+    private static final String testString = "\u00e9\u3042"; // "éあ"
+
+    @DataProvider
+    public Object[][] encodings() {
+        return new Object[][]{
+                {StandardCharsets.ISO_8859_1},
+                {StandardCharsets.US_ASCII},
+                {StandardCharsets.UTF_8},
+                {StandardCharsets.UTF_16},
+                {StandardCharsets.UTF_16BE},
+                {StandardCharsets.UTF_16LE},
+        };
+    }
+
+    @Test (dataProvider = "encodings")
+    public void testOutputStreamWriter(Charset stdCharset) throws IOException {
+        var ba = new ByteArrayOutputStream();
+        var ps = new PrintStream(ba, true, stdCharset);
+        var expected = new String(testString.getBytes(stdCharset), stdCharset);
+
+        // tests OutputStreamWriter's encoding explicitly
+        var osw = new OutputStreamWriter(ps);
+        assertEquals(Charset.forName(osw.getEncoding()), stdCharset);
+
+        // tests roundtrip result
+        osw.write(testString);
+        osw.flush();
+        var result = ba.toString(stdCharset);
+        assertEquals(result, expected);
+    }
+
+    @Test (dataProvider = "encodings")
+    public void testPrintWriter(Charset stdCharset) throws IOException {
+        var ba = new ByteArrayOutputStream();
+        var ps = new PrintStream(ba, true, stdCharset);
+        var expected = new String(testString.getBytes(stdCharset), stdCharset);
+
+        // tests roundtrip result
+        var pw = new PrintWriter(ps);
+        pw.write(testString);
+        pw.flush();
+        var result = ba.toString(stdCharset);
+        assertEquals(result, expected);
+    }
+
+    @Test (dataProvider = "encodings")
+    public void testPrintStream(Charset stdCharset) throws IOException {
+        var ba = new ByteArrayOutputStream();
+        var ps = new PrintStream(ba, true, stdCharset);
+        var expected = new String(testString.getBytes(stdCharset), stdCharset);
+
+        // tests PrintStream's charset explicitly
+        var psWrapper = new PrintStream(ps);
+        assertEquals(psWrapper.charset(), stdCharset);
+
+        // tests roundtrip result
+        psWrapper.print(testString);
+        psWrapper.flush();
+        var result = ba.toString(stdCharset);
+        assertEquals(result, expected);
+    }
+}