#863 use StringBuilderWriter to toString methods

resulting in a faster toString generation.

src/main/java/org/json/JSONArray.java

@@ -5,7 +5,6 @@ Public Domain.
  */
 
 import java.io.IOException;
-import java.io.StringWriter;
 import java.io.Writer;
 import java.lang.reflect.Array;
 import java.math.BigDecimal;
@@ -1695,7 +1694,7 @@ public class JSONArray implements Iterable<Object> {
      */
     @SuppressWarnings("resource")
     public String toString(int indentFactor) throws JSONException {
-        StringWriter sw = new StringWriter();
+        Writer sw = new StringBuilderWriter();
         return this.write(sw, indentFactor, 0).toString();
     }
 

src/main/java/org/json/JSONObject.java

@@ -6,7 +6,6 @@ Public Domain.
 
 import java.io.Closeable;
 import java.io.IOException;
-import java.io.StringWriter;
 import java.io.Writer;
 import java.lang.annotation.Annotation;
 import java.lang.reflect.Field;
@@ -2227,7 +2226,7 @@ public class JSONObject {
      */
     @SuppressWarnings("resource")
     public static String quote(String string) {
-        StringWriter sw = new StringWriter();
+        Writer sw = new StringBuilderWriter();
         try {
             return quote(string, sw).toString();
         } catch (IOException ignored) {
@@ -2558,7 +2557,7 @@ public class JSONObject {
      */
     @SuppressWarnings("resource")
     public String toString(int indentFactor) throws JSONException {
-        StringWriter w = new StringWriter();
+        Writer w = new StringBuilderWriter();
         return this.write(w, indentFactor, 0).toString();
     }
 

src/main/java/org/json/StringBuilderWriter.java

@@ -0,0 +1,82 @@
+package org.json;
+
+import java.io.IOException;
+import java.io.Writer;
+
+/**
+ * Performance optimised alternative for {@link java.io.StringWriter}
+ * using internally a {@link StringBuilder} instead of a {@link StringBuffer}.
+ */
+class StringBuilderWriter extends Writer {
+    private final StringBuilder builder;
+
+    StringBuilderWriter() {
+        builder = new StringBuilder();
+        lock = builder;
+    }
+
+    StringBuilderWriter(int initialSize) {
+        if (initialSize < 0) {
+            throw new IllegalArgumentException("Negative buffer size");
+        }
+        builder = new StringBuilder(initialSize);
+        lock = builder;
+    }
+
+    @Override
+    public void write(int c) {
+        builder.append((char) c);
+    }
+
+    @Override
+    public void write(char cbuf[], int offset, int length) {
+        if ((offset < 0) || (offset > cbuf.length) || (length < 0) ||
+                ((offset + length) > cbuf.length) || ((offset + length) < 0)) {
+            throw new IndexOutOfBoundsException();
+        } else if (length == 0) {
+            return;
+        }
+        builder.append(cbuf, offset, length);
+    }
+
+    @Override
+    public void write(String str) {
+        builder.append(str);
+    }
+
+    @Override
+    public void write(String str, int offset, int length) {
+        builder.append(str, offset, offset + length);
+    }
+
+    @Override
+    public StringBuilderWriter append(CharSequence csq) {
+        write(String.valueOf(csq));
+        return this;
+    }
+
+    @Override
+    public StringBuilderWriter append(CharSequence csq, int start, int end) {
+        if (csq == null) csq = "null";
+        return append(csq.subSequence(start, end));
+    }
+
+    @Override
+    public StringBuilderWriter append(char c) {
+        write(c);
+        return this;
+    }
+
+    @Override
+    public String toString() {
+        return builder.toString();
+    }
+
+    @Override
+    public void flush() {
+    }
+
+    @Override
+    public void close() throws IOException {
+    }
+}