PrintWriter类

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：

import java.io.IOException;
import java.io.PrintWriter;
import java.io.FileWriter;
import java.io.File;

public class PrintWriterDemo {

    public static void main(String[] args) {
        PrintWriter pw = null;
        String name = "张松伟";
        int age = 22;
        float score = 32.5f;
        char sex = '男';
        try {
            pw = new PrintWriter(new FileWriter(new File("e:\file.txt")), true);
            pw.printf("姓名：%s;年龄：%d;性别：%c;分数：%5.2f;", name, age, sex, score);
            pw.println();
            pw.println("多多指教");
            pw.write(name.toCharArray());
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            pw.close();
        }
    }
}