StringWriter在Java中的重要性是什么？

public class StringWriter extends Writer

import java.io.*;
public class StringWriterTest {
   public static void main(String args[]) {
      String str = "Welcome to Tutorials Point";
      try {
         StringWriter sw = new StringWriter();
         sw.write(str);
         StringBuffer sb = new StringBuffer();
         sb = sw.getBuffer();
         System.out.println("StringBuffer: "+ sb);
         System.out.println("String written by StringWriter: "+ sw);
         sw.close();
      } catch (IOException ioe) {
         System.out.println(ioe);
      }
   }
}

StringBuffer: Welcome to Tutorials Point
String written by StringWriter: Welcome to Tutorials Point