怎么理解Two's complement

在Java里整数的表示就用的是Two's complement

转换方法：一个整数n, 想要得到-n的二进制表示，则可将n的二进制写出来，然后挨个翻转，完成后加1即可。比如 8 -> 00001000 -> 11110111 -> 11111000 -> -8

如此来算，则
00000001 ->1, 00000010 -> 2, ... , 01111111 -> 127
11111111 -> -1, 11111110 -> -2, ... , 10000001 -> -127, 10000000 -> -128

也可以这么想，n和-n加起来就是00000000 (往更高一位进一个1，100000000)

好处：加减都可以换成加法了。12-60 = 12 + (-60)

数学上怎么理解:
-n就是0 - n，然后0我们可以想像成100000000, 11111111-n就是把n 挨个翻转，但是11111111还比“0“多减了个1，所以我们要把结果加1. （就是减法上借位的思想）。

01-18-2019

刷题:
Leetcode 819，
很简单，需要补充的：String methods, Collections (Map, Set), Map.Entry methods. Regex

Core Java Chapter 2 finished

1-14-2019

Finished Core Java Chapter 1

01-10-2019

Udemy Web Developer Bootcamp Section4 finished.
form, input, label etc.

01-09-2019

农历生日

路上看microservices

看Core Java I 11th edition
Read about 11 buzzwords (Chapter 1.2)
Chapter 1
1.2 11 buzzwords

1. Simple
2. Object-Oriented
3. Distributed
4. Robust
5. Secure
6. Arcitecture-Neutral (JVM, Java runtime system)
7. Portable (size of primitive dat types are specified, for example int is always 32bit.)
8. Interpreted (jshell in Java 9 for rapid and exploratory programming)
9. High-Performance (just-in-time compilers)
10. Multithreaded (use more processors in parallel)
11. Dynamic

1.3 Java applets and the Internet

    applets: Java programs that work on web pages (need a supporting browser)

But actually Flash became popular.

Nowadays usually can use HTML and Javascript

打表学习从2019.1.10开始

用小本本记下来每天做了什么，学到了什么。