常用类，接口

ByteArrayInputStream内存读入字节流

ByteArrayOutputStream内存写出字节流

用内存处理io操作

    public static void main(String[] args) throws IOException {
        InputStream in =new ByteArrayInputStream("wahahahha".getBytes());
        OutputStream out = new ByteArrayOutputStream();
        int temp;
        while ((temp=in.read())!=-1) {
            out.write(temp);
        }
        System.out.println(out.toString().toUpperCase());
        in.close();
        out.close();
    }

console打印跟java相关的系统属性

System.getProperties().list(System.out);

设置编码格式（字符集），别瞎鸡巴乱设置，会抛异常；编码解码标准不统一就会乱码

String.getBytes(String charsetName) throws UnsupportedEncodingException

日常开发输出数据使用PrintStream或PrintWriter（输出中文）；输入数据使用Scanner类

序列化输出和反序列化输入示例：

        ObjectOutputStream oo = new ObjectOutputStream(new FileOutputStream(file));
        Testob testob = new Testob(15, "1111", new Date());
        oo.writeObject(testob);

        ObjectInputStream oi = new ObjectInputStream(new FileInputStream(file));
        System.out.println((Testob) oi.readObject());