JAVA IO - FileWriter&FileReader

FileWriter 自己是FileOutputStream的一個包裝器,將使用默認的編碼格式輸出chars. FileWriter的構造函數有一個能夠表示若是文件已存在，是否向文件中追加的參數。

FileWriter通常用來將連續的字符串輸出到文件中, 要咱們本身調用flush方法纔會將字符串寫入文件中。

固然FileWriter和FileOutputStream均可以向文件中寫入內容，後者更底層一些，前者傾向於字符串的輸出。

 FileWriter is meant for writing streams of characters. It will use the default character encoding and the default byte-buffer size. In other words, it is a wrapper class of FileOutputStream for convenience. Therefore, to specify these values yourself, consider using a FileOutputStream.

 

FileWriter is a subclass of OutputStreamWriter class that is used to write text (as opposed to binary data) to a file.

So if you want to handle binary data such as image file as in your case, you should be using FileOutputStream instead of FileWriter.

import java.io.FileWriter;
import java.io.Writer;

public class WriterTest {

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		// TODO Auto-generated method stub
		try {
			Writer writer = new FileWriter("helloworld.txt");
			String str = "hello test1";
			writer.write(str);
			writer.flush();
			writer.close();
		} catch (Exception e) {
            e.printStackTrace();
		}
	}

}

 

相似的FileReader和FileInputStream也有相似的關係

Whether to use streams of bytes or characters? It really depends. Both have buffers. InputStream/OutputStream provide more flexibility, but will make your 「simple」 program complex. On the other hand, FileWriter/FileReader give a neat solution but you lose the control.

importjava.io.FileReader;

importjava.io.IOException;

importjava.io.Reader;

 

publicclassFileOperationTest {

 

  publicstaticvoidmain(String[] args)

      throwsIOException {

    Reader in =newFileReader("helloworld.txt");

    charcs[] =newchar[1024];

    intlen = -1;

    while((len = in.read(cs)) != -1) {

      System.out.println(newString(cs,0, len));

    }

    in.close();

  }

}