类 CachedStringWriter

所有已实现的接口:
Closeable, Flushable, Appendable, AutoCloseable

public class CachedStringWriter extends NoLockStringWriter
提供某些高速场景下的writer,无需分配char[]

     Writer writer = CachedStringWriter.buffers.get();
     template.renderTo(writer);
     String result = writer.toString();