the reasonable man adapts himself to the world;the unreasonable one persists in trying to adapt the world to himself. —萧伯纳
相信自己看得懂就看得懂了,相信自己能写下去,我就开始写了.其实也简单—泥沙砖瓦浆木匠
today , i am writing my java notes about <编写高质量代码改善java程序的151个建议> -秦小波.
three pieces[1-3]:
1.don't code by confusing letters in the constants and variables [不要在常量和变量中出现易混淆的字母]
2.don't change the constants into the variable. [莫让常量蜕变成变量]
3.make the the types of ternary operators the same. [三元操作符的类型务必一致]
from the book:
outputs:
1
<code>2</code><code> </code>
(unbelieved?just ctrl c + ctrl v run the code !)
in my words:
‘1l’is not ‘11’. but we always code by the confusing things .
then bebug for a long time , finally we will laught at ourselves with
the computer and codes face to face.”what fucking are the
coder?”lol,smile ! carm down , because u r so lucky to read this . i
will tell some excemples to keep them away. away ? really away?
step 1: somthing about coding standards
constants should always be all-uppercase, with underscores to separatewords. [常量都要大写,用下划线分开]
see a case from my project itp:
camel case:[变量命名驼峰原则,自然你也可以选择其他的法则等]
if u wanna do it , right now ! it can make your codes more beautiful and clean! amazing ! u learned it , keep on!!!
#please remeber the camel , then u can write a nice code.
step 2: somthing can make your program easier to understand
some letters should not be used with the numbers,like l o … they
are the brother of the numbers.but we can do some to avoid. like use
‘l’ , and write some notes about them.
a magical demo:
#i think the demo is bad. rand_cosnt is not a constant and we never do that.
what is constants ?
constants are immutable values which are known at compile time and do not change for the life of the program.but if the project is too large to manage.there will be a problem.let me show u!
example:
class a's goodnumber = 0.618
now we change a.java –> goodnumber to “0.6180339887”
“javac a.java”then “java b” , we will find the outputs is the same:
why??????????????????
just see the class of b, use “ javap –c b”:
#3: ldc #3 // string class a's goodnumber = 0.618
ok , we see! the last interface a was already in the class b. so we can “javac b.java”to deal.
all in all ,
a best way store constants : static fianl xxx static object getxxx()
it shows the java dynamic advantage and a constant principle.
<code>false</code>
see the compiled code ,use “javap –c client03”,we will see:
the transformation rules about ternary operators.
三元操作符类型的转换规则：
1.若两个操作数不可转换，则不做转换，返回值为object 类型。
2.若两个操作数是明确类型的表达式（比如变量），则按照正常的二进制数字来转换，int 类型转换为long 类型，long 类型转换为float 类型等。
3.若两个操作数中有一个是数字s，另外一个是表达式，且其类型标示为t，那么，若数字s 在t 的范围内，则转换为t 类型；若s 超出了t 类型的范围，则t 转换为s类型（可以参考“建议22”，会对该问题进行展开描述）。
4.若两个操作数都是直接量数字（literal） ，则返回值类型为范围较大者。