目录
- I. Intro —— 写java的初体验，解了problem set 0
- II. Testing —— 不同test的区别
- III. Specification —— 不同spec的区别，以及如何写好
- IIII. Snapshot Diagram —— 不同符号的含义
I. Intro
1. Coding Descipline
- Safe from bugs
- Easy to understand
- Ready for change
2. Java语法memo
-
继承
以官网doc的例子。Mountain / Road / Tandem Bike三种，都是Bicycle，但是增加了不同的feature。因而，OOP中，允许继承。此时，Bicycle是其他三者的superclass；Mountain / Road / Tandem Bike则是subclasses。
Bicyle的继承
Syntax用了```extends``，继承写起来，大概长这样👇：
public class MountainBike extends Bicycle {
// the MountainBike subclass has
// one field
public int seatHeight;
// the MountainBike subclass has
// one constructor
public MountainBike(int startHeight, int startCadence,
int startSpeed, int startGear) {
super(startCadence, startSpeed, startGear);
seatHeight = startHeight;
}
// the MountainBike subclass has
// one method
public void setHeight(int newValue) {
seatHeight = newValue;
}
}
-
if语句: "?"
if ( a > b ) {
max = a;
} else {
max = b
}
简写成
max = (a > b) ? a: b;
3. Problem set 0心得
- 做problem set 0的时候，放弃了最后三题，看不懂atan的数学问题。希望后面的problem set不要出现一样的...🤦♂️。
- 有一个之前完全没有注意的，就是magic number。忽然就声明了一个数字，其实违反了easy to understand。合适的方法是，声明一个变量，然后comment它的含义。有时候需要final它。
- unit test的重要性，下assert，做好每个unit的debug。
-
float和double区别在于32bit和64bit，所以用double更安全。 - 前面那个javadoc，也从没写过，好像挺方便的。写javadoc，有一个关键的准则，是：NEVER talk about local variables of the method or private fields.
NEVER talk about local variables of the method or private fields.
模板大概是：
/**
brief description, what is this method for?
@param parameterName What is the parameter for?
@return value What is the value meaning?
**/
II. Testing
1. Residual defect rates
- 1 - 10 defects/kloc: Typical industry software.
- 0.1 - 1 defects/kloc: High-quality validation. The Java libraries might achieve this level of correctness.
- 0.01 - 0.1 defects/kloc: The very best, safety-critical validation. NASA and aerospace companies can achieve this level.
kloc : 1000 lines of source code.
2. Testing
- Test-first programming. Write tests before you write code.
- Partitioning and boundaries for choosing test cases systematically.
- White box testing and statement coverage for filling out a test suite.
- Unit-testing each module in isolation as much as possible.
- Automated regression testing to keep bugs from coming back.
2.1 Unit Tests
Testing modules in isolation leads to much easier debugging.
2.2 Regression Testing
Regression意味着，在改bug-A或者增加feature-B的时候，又多了新的bug-B。在test-first debugging中，把之前的bug-A的test case增加到test suite中，这样写完B后，可以确定A不会再发生。
3. 心得
之前对unit test没啥概念，意味只要分模块写code就好。但是，每个模块的debugging和test case，要考虑到模块中，也就是test-first programming的重要性。Write tests before you write code.
III. Specification
1. underdetermined specs & nondeterminism 定义
- deterministic spec: 1 input → 1 output
- under-deterministic spec: 1 input → >1 outputs
- under-deterministic spec can have determined implementation
2. declarative vs. operational specs 定义
- operational specs → spec中写了method运行的步骤
- declarative specs (better) → spec不提供内部的步骤，只提供outcome的properties
3. 好的specs长什么样？
- better spec👍 → weaker precondition🔽 & stronger postcondition🔼
4. 如何写好spec？
- brief & clear & structured
- coherent inputs
- no global variables & no printing (instead of returning)
- no making internal helper methods public （helper method only for local use）
IIII. Snapshot Diagram
- → variable
- ⇒ final
- → ⚪
- → ⭕(double circles)
-
List
Lists -
Set
Set -
Map
Map
6.005.1x，自学的第一个礼拜。💻🔨
整个版面乱成一锅粥。或许应该再开一个post，来整理知识点吧。🤦♂️
Ronn Liu 🙋♂️
2019/01/01 - 2019/01/06 📌
