介紹

FileReader是用於讀取字元流的類，繼承於InputStreamReader，如果要讀取原始位元組流，需要使用InputStream。

FileWriter是用於寫入字元流的類，繼承於OutputStreamWriter，如果要寫入原始位元組流，需要使用OutptuStream。

原始碼

FileReader

package java.io;

public class FileReader extends InputStreamReader {

    public FileReader(String fileName) throws FileNotFoundException {
        super(new FileInputStream(fileName));
    }

    public FileReader(File file) throws FileNotFoundException {
        super(new FileInputStream(file));
    }

    public FileReader(FileDescriptor fd) {
        super(new FileInputStream(fd));
    }
}
 

從中，我們可以看出FileReader是基於InputStreamReader實現的。 

FileWriter

package java.io;

public class FileWriter extends OutputStreamWriter {

    public FileWriter(String fileName) throws IOException {
        super(new FileOutputStream(fileName));
    }

    public FileWriter(String fileName, boolean append) throws IOException {
        super(new FileOutputStream(fileName, append));
    }

    public FileWriter(File file) throws IOException {
        super(new FileOutputStream(file));
    }

    public FileWriter(File file, boolean append) throws IOException {
        super(new FileOutputStream(file, append));
    }

    public FileWriter(FileDescriptor fd) {
        super(new FileOutputStream(fd));
    }
}
 

執行結果：
c1=字
buf=流示例0123456

原文：http://www.cnblogs.com/skywang12345/p/io_22.html