Limited to Writer.of(StringBuilder)

Author: mkarg

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

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1996, 2024, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1996, 2025, 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
@@ -37,8 +37,8 @@
  * {@code IOException}.
  *
  * @apiNote
- * {@link Writer#of(Appendable)} provides a method to write into any
- * {@link Appendable} that may be more efficient than {@code StringWriter}.
+ * {@link Writer#of(StringBuilder)} provides a method to write into an existing
+ * {@link StringBuilder} that may be more efficient than {@code StringWriter}.
  *
  * @author      Mark Reinhold
  * @since       1.1

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

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1996, 2024, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1996, 2025, 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
@@ -146,31 +146,25 @@ public void close() throws IOException {
     }
 
     /**
-     * Returns a {@code Writer} that writes characters into an
-     * {@code Appendable}. The writer is initially open and writing appends
-     * after the last character in the appendable.
-     *
-     * <p> If the appendable is a {code Writer}, it is returned.
+     * Returns a {@code Writer} that writes characters into a
+     * {@code StringBuilder}. The writer is initially open and writing appends
+     * after the last character in the string builder.
      *
      * <p> The resulting writer is not safe for use by multiple
      * concurrent threads. If the writer is to be used by more than one
      * thread it should be controlled by appropriate synchronization.
      *
-     * <p> If the appendable changes while the writer is open, e.g. the length
+     * <p> If the string builder changes while the writer is open, e.g. the length
      * changes, the behavior is undefined.
      *
-     * @param a {@code Appendable} consuming the character stream.
-     * @return a {@code Writer} which writes characters into {@code a}, or
-     *         {@code a} if it is a {@code Writer}.
-     * @throws NullPointerException if {@code a} is {@code null}
+     * @param sb {@code StringBuilder} consuming the character stream.
+     * @return a {@code Writer} which writes characters into {@code sb}.
+     * @throws NullPointerException if {@code sb} is {@code null}
      *
      * @since 25
      */
-    public static Writer of(final Appendable a) {
-        Objects.requireNonNull(a);
-
-        if (a instanceof Writer w)
-            return w;
+    public static Writer of(final StringBuilder sb) {
+        Objects.requireNonNull(sb);
 
         return new Writer() {
             private boolean isClosed;
@@ -184,7 +178,7 @@ private void ensureOpen() throws IOException {
             @Override
             public void write(int c) throws IOException {
                 ensureOpen();
-                a.append((char) c);
+                sb.append((char) c);
             }
 
             @Override
@@ -194,73 +188,49 @@ public void write(char[] cbuf, int off, int len) throws IOException {
                 if (len == 0) {
                     return;
                 }
-                switch (a) {
-                    case StringBuilder sb -> sb.append(cbuf, off, len);
-                    case StringBuffer sb -> sb.append(cbuf, off, len);
-                    case CharBuffer cb -> cb.put(cbuf, off, len);
-                    default -> {
-                        for (int i = 0; i < len; i++)
-                            a.append(cbuf[off + i]);
-                    }
-                }
+                sb.append(cbuf, off, len);
             }
 
             @Override
             public void write(String str) throws IOException {
                 ensureOpen();
-                switch (a) {
-                    case StringBuilder sb -> sb.append(str);
-                    case StringBuffer sb -> sb.append(str);
-                    case CharBuffer cb -> cb.put(str);
-                    default -> a.append(str);
-                }
+                sb.append(str);
             }
 
             @Override
             public void write(String str, int off, int len) throws IOException {
                 ensureOpen();
-                a.append(str, off, off + len);
+                sb.append(str, off, off + len);
             }
 
             @Override
             public Writer append(CharSequence csq) throws IOException {
                 ensureOpen();
-                a.append(csq);
+                sb.append(csq);
                 return this;
             }
 
             @Override
             public Writer append(CharSequence csq, int start, int end) throws IOException {
                 ensureOpen();
-                a.append(csq, start, end);
+                sb.append(csq, start, end);
                 return this;
             }
 
             @Override
             public Writer append(char c) throws IOException {
                 ensureOpen();
-                a.append(c);
+                sb.append(c);
                 return this;
             }
 
             @Override
             public void flush() throws IOException {
                 ensureOpen();
-                implFlush();
-            }
-
-            private void implFlush() throws IOException {
-                if (a instanceof Flushable f)
-                    f.flush();
             }
 
             @Override
             public void close() throws IOException {
-                if (isClosed)
-                    return;
-                implFlush();
-                if (a instanceof Closable c)
-                    c.close();
                 isClosed = true;
             }
         };

src/java.base/share/classes/java/nio/X-Buffer.java.template

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2000, 2024, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2000, 2025, 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

test/jdk/java/io/Writer/Of.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2024, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2025, 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
@@ -24,10 +24,6 @@
 import java.io.Writer;
 import java.io.StringWriter;
 import java.io.IOException;
-import java.io.StringWriter;
-import java.nio.ByteBuffer;
-import java.nio.CharBuffer;
-import java.nio.ReadOnlyBufferException;
 import java.util.function.Supplier;
 
 import org.testng.annotations.*;
@@ -36,7 +32,7 @@
 
 /*
  * @test
- * @bug 1234567
+ * @bug 8353795
  * @summary Check for expected behavior of Writer.of().
  * @run testng Of
  */
@@ -56,10 +52,7 @@ public String toString() {
     @DataProvider
     public static Config[] writers() {
         var sw = new StringWriter();
-        var sbuf = new StringBuffer();
         var sbld = new StringBuilder();
-        var dcb = ByteBuffer.allocateDirect(CONTENT.length() * 2).asCharBuffer();
-        var wcb = CharBuffer.wrap(new char[CONTENT.length()]);
         var w = new Writer() {
             private String s = "";
             private boolean isClosed;
@@ -112,43 +105,10 @@ public String toString() {
                 return s;
             }
         };
-        var a = new Appendable() {
-            private String s = "";
-
-            @Override
-            public Appendable append(char c) throws IOException {
-                s += c;
-                return this;
-            }
-
-            @Override
-            public Appendable append(CharSequence csq) throws IOException {
-                s += String.valueOf(csq);
-                return this;
-            }
-
-            @Override
-            public Appendable append(CharSequence csq, int start, int end)
-                    throws IOException {
-                s += String.valueOf(csq).subSequence(start, end);
-                return this;
-            }
-
-            @Override
-            public String toString() {
-                return s;
-            }
-        };
         return new Config[] {
             new Config("StringWriter", sw, sw::toString),
-            new Config("StringBuffer", Writer.of(sbuf), sbuf::toString),
             new Config("StringBuilder", Writer.of(sbld), sbld::toString),
-            new Config("Direct CharBuffer", Writer.of(dcb),
-                    () -> { dcb.flip(); return dcb.toString(); }),
-            new Config("Wrapped CharBuffer", Writer.of(wcb),
-                    () -> { wcb.flip(); return wcb.toString(); }),
             new Config("Custom Writer", w, w::toString),
-            new Config("Custom Appendable", Writer.of(a), a::toString)
         };
     }