PrintWriter是一种过滤流，也是一种处理流，即能对字节流和字符流进行处理。

1.查询API后，我们发现，会有八种构造方法。即：

• ( file)

  Creates a new PrintWriter, without automatic line flushing, with the specified file.
  ( file,  csn)

  Creates a new PrintWriter, without automatic line flushing, with the specified file and charset.
  ( out)

  Creates a new PrintWriter, without automatic line flushing, from an existing OutputStream.
  ( out, boolean autoFlush)

  Creates a new PrintWriter from an existing OutputStream.
  ( fileName)

  Creates a new PrintWriter, without automatic line flushing, with the specified file name.
  ( fileName,  csn)

  Creates a new PrintWriter, without automatic line flushing, with the specified file name and charset.
  ( out)

  Creates a new PrintWriter, without automatic line flushing.
  ( out, boolean autoFlush)

  Creates a new PrintWriter.

2.实现了三种接口。

1) Closeable接口， 所以它有pw.close()方法来实现对PrintWriter的关闭。

2) Flushable接口，所以它有pw.flush()方法来实现人为的刷新。

3) Appendable接口，所以它有pw.append(char c)方法来向此输出流中追加指定字符，等价于print().

3.方法自寻查询api

4.举例：

1 import java.io.IOException; 2 import java.io.PrintWriter; 3 import java.io.FileWriter; 4 import java.io.File; 5  6 public class PrintWriterDemo { 7  8     public static void main(String[] args) { 9         PrintWriter pw = null;10         String name = "张松伟";11         int age = 22;12         float score = 32.5f;13         char sex = '男';14         try {15             pw = new PrintWriter(new FileWriter(new File("e:\\file.txt")), true);16             pw.printf("姓名：%s;年龄：%d;性别：%c;分数：%5.2f;", name, age, sex, score);17             pw.println();18             pw.println("多多指教");19             pw.write(name.toCharArray());20         } catch (IOException e) {21             e.printStackTrace();22         } finally {23             pw.close();24         }25     }26 }