BufferedWriter flush方法

BufferedWriter br = new BufferedWriter(
    new OutputStreamWriter(
        new FileOutputStream(file)), 40960);
char[] str = new char[40959];
for (int i = 0 ; i < 40959; i++) {
    str[i] = 'a';
}
long time = System.currentTimeMillis();
br.write(str);
System.out.println(System.currentTimeMillis() - time);
time = System.currentTimeMillis();
br.flush();
System.out.println(System.currentTimeMillis() - time);



输出：

    0
    2