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：
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PrintWriter(File file)Creates a new PrintWriter, without automatic line flushing, with the specified file.
PrintWriter(File file, String csn)Creates a new PrintWriter, without automatic line flushing, with the specified file and charset.
PrintWriter(OutputStream out)Creates a new PrintWriter, without automatic line flushing, from an existing OutputStream.
PrintWriter(OutputStream out, boolean autoFlush)Creates a new PrintWriter from an existing OutputStream.
PrintWriter(String fileName)Creates a new PrintWriter, without automatic line flushing, with the specified file name.
PrintWriter(String fileName, String csn)Creates a new PrintWriter, without automatic line flushing, with the specified file name and charset.
PrintWriter(Writer out)Creates a new PrintWriter, without automatic line flushing.
PrintWriter(Writer 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 }