PrintWriter类

Posted 2020-08-03 laurdawn

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：

• 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 }