字符流：FileReader/FileWriter

String instr = "E:\\text.txt";
String oustr = "E:\\b .txt";
FileReader reader = null;
FileWriter writer = null;
char[] b = new char[8];
int readData = 0;
long t1 = System.currentTimeMillis();
try {
    reader = new FileReader(instr);
    writer = new FileWriter(oustr);
    while ((readData = reader.read(b)) != -1) {
        writer.write(b, 0, b.length);
    }
    long t2 = System.currentTimeMillis();
    System.out.println("花费时间：" + (t2 - t1));

} catch (IOException e) {
    e.printStackTrace();
} finally {
    try {
        if (reader != null) {
            reader.close();
        }
    } catch (IOException e) {
        e.printStackTrace();
    }

    try {
        if (writer != null) {
            writer.close();
        }
    } catch (IOException e) {
        e.printStackTrace();
    }
}