8333396: Use StringBuilder internally for java.text.Format.* formatting

Reviewed-by: naoto, liach, jlu

src/java.base/share/classes/java/text/StringBufFactory.java

@@ -0,0 +1,216 @@
+/*
+ * Copyright (c) 2024, Alibaba Group Holding Limited. 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.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * 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.
+ */
+
+package java.text;
+
+import java.text.Format.StringBuf;
+
+/**
+ * {@code StringBufFactory} creates implementations of {@code Format.StringBuf},
+ * which is an interface with the minimum overlap required to support {@code StringBuffer}
+ * and {@code StringBuilder} in {@code Format}. This allows for {@code StringBuilder} to be used
+ * in place of {@code StringBuffer} to provide performance benefits for JDK internal
+ * {@code Format} subclasses.
+ */
+final class StringBufFactory {
+
+    private StringBufFactory() {
+    }
+
+    static StringBuf of(StringBuffer sb) {
+        return new StringBufferImpl(sb);
+    }
+
+    static StringBuf of(StringBuilder sb) {
+        return new StringBuilderImpl(sb);
+    }
+
+    static StringBuf of() {
+        return new StringBuilderImpl();
+    }
+
+    final static class StringBufferImpl implements StringBuf {
+        private final StringBuffer sb;
+
+        StringBufferImpl(StringBuffer sb) {
+            this.sb = sb;
+        }
+
+        @Override
+        public int length() {
+            return sb.length();
+        }
+
+        @Override
+        public String substring(int start, int end) {
+            return sb.substring(start, end);
+        }
+
+        @Override
+        public String substring(int start) {
+            return sb.substring(start);
+        }
+
+        @Override
+        public StringBuf append(char c) {
+            sb.append(c);
+            return this;
+        }
+
+        @Override
+        public StringBuf append(String str) {
+            sb.append(str);
+            return this;
+        }
+
+        @Override
+        public StringBuf append(int i) {
+            sb.append(i);
+            return this;
+        }
+
+        @Override
+        public StringBuf append(char[] str, int offset, int len) {
+            sb.append(str, offset, len);
+            return this;
+        }
+
+        @Override
+        public StringBuf append(CharSequence s, int start, int end) {
+            sb.append(s, start, end);
+            return this;
+        }
+
+        @Override
+        public StringBuf append(StringBuffer asb) {
+            sb.append(asb);
+            return this;
+        }
+
+        @Override
+        public boolean isProxyStringBuilder() {
+            return false;
+        }
+
+        @Override
+        public StringBuffer asStringBuffer() {
+            return sb;
+        }
+
+        @Override
+        public StringBuilder asStringBuilder() {
+            throw new AssertionError("Can't cast StringBuffer to StringBuilder");
+        }
+
+        @Override
+        public String toString() {
+            return sb.toString();
+        }
+    }
+
+    final static class StringBuilderImpl implements StringBuf {
+        private final StringBuilder sb;
+
+        StringBuilderImpl(StringBuilder sb) {
+            this.sb = sb;
+        }
+
+        StringBuilderImpl() {
+            this.sb = new StringBuilder();
+        }
+
+        @Override
+        public int length() {
+            return sb.length();
+        }
+
+        @Override
+        public String substring(int start, int end) {
+            return sb.substring(start, end);
+        }
+
+        @Override
+        public String substring(int start) {
+            return sb.substring(start);
+        }
+
+        @Override
+        public StringBuf append(char c) {
+            sb.append(c);
+            return this;
+        }
+
+        @Override
+        public StringBuf append(String str) {
+            sb.append(str);
+            return this;
+        }
+
+        @Override
+        public StringBuf append(int i) {
+            sb.append(i);
+            return this;
+        }
+
+        @Override
+        public StringBuf append(char[] str, int offset, int len) {
+            sb.append(str, offset, len);
+            return this;
+        }
+
+        @Override
+        public StringBuf append(CharSequence s, int start, int end) {
+            sb.append(s, start, end);
+            return this;
+        }
+
+        @Override
+        public StringBuf append(StringBuffer asb) {
+            sb.append(asb);
+            return this;
+        }
+
+
+        @Override
+        public boolean isProxyStringBuilder() {
+            return true;
+        }
+
+        @Override
+        public StringBuffer asStringBuffer() {
+            throw new AssertionError("Can't cast StringBuilder to StringBuffer");
+        }
+
+        @Override
+        public StringBuilder asStringBuilder() {
+            return sb;
+        }
+
+        @Override
+        public String toString() {
+            return sb.toString();
+        }
+    }
+}