//每次读取的字节长度，一般都是1024的倍数

private static final int BUF_SIZE = 1024;

public static void main(String[] args) {

// TODO Auto-generated method stub

FileReader fr = null;

FileWriter fw = null;

try {

fr = new FileReader("demo.txt");

fw = new FileWriter("cope.txt");

//定义一个数组容器，用来装读取的字节

char[] buf = new char[BUF_SIZE];

int len = 0;

while ((len = fr.read(buf)) != -1) {

fw.write(buf, 0, len);

}

} catch (Exception e) {

// TODO: handle exception

throw new RuntimeException("复制失败");

}finally {

if (fr != null) {

try {

fr.close();

} catch (Exception e2) {

// TODO: handle exception

}

}

if (fw != null) {

try {

fw.close();

} catch (Exception e2) {

// TODO: handle exception

}

}

}

}