-
Notifications
You must be signed in to change notification settings - Fork 0
Commit
This commit does not belong to any branch on this repository, and may belong to a fork outside of the repository.
- Loading branch information
Showing
33 changed files
with
5,650 additions
and
3 deletions.
There are no files selected for viewing
Large diffs are not rendered by default.
Oops, something went wrong.
Large diffs are not rendered by default.
Oops, something went wrong.
Large diffs are not rendered by default.
Oops, something went wrong.
Large diffs are not rendered by default.
Oops, something went wrong.
Large diffs are not rendered by default.
Oops, something went wrong.
Large diffs are not rendered by default.
Oops, something went wrong.
Large diffs are not rendered by default.
Oops, something went wrong.
Large diffs are not rendered by default.
Oops, something went wrong.
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Loading
Sorry, something went wrong. Reload?
Sorry, we cannot display this file.
Sorry, this file is invalid so it cannot be displayed.
Loading
Sorry, something went wrong. Reload?
Sorry, we cannot display this file.
Sorry, this file is invalid so it cannot be displayed.
Loading
Sorry, something went wrong. Reload?
Sorry, we cannot display this file.
Sorry, this file is invalid so it cannot be displayed.
Loading
Sorry, something went wrong. Reload?
Sorry, we cannot display this file.
Sorry, this file is invalid so it cannot be displayed.
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,70 @@ | ||
| --- | ||
| title: Basic C note | ||
| date: 2019-7-5 | ||
| tags: | ||
| - learning note | ||
|
|
||
| categories: learning note | ||
| --- | ||
| # Basic C note | ||
|
|
||
| ## 一、 文本显示 | ||
|
|
||
| - printf用于输出文字 | ||
| ``` | ||
| #include <stdio.h> | ||
| int main() | ||
| { | ||
| printf("我是小仙女,\n我长得很漂亮。\n"); | ||
| return 0; | ||
| } | ||
| ``` | ||
| ## 二、数据类型 | ||
|
|
||
| ``` | ||
| //standard io标准流输出 | ||
| #include <studio.h> | ||
| int main() | ||
| { | ||
| //char 字符类型，主要用来显示给人看 | ||
| //int 整型， 整数型数字， 可以用来计算。 | ||
| printf("hello\n"); | ||
| printf("%d\n",1); | ||
| printf("%d大于%d",2,1); //2替换第一个%d,1替换第二个%d | ||
| } | ||
| ``` | ||
| - 要显示字符型，我们只要直接写在两个引号里就可以了，写了什么就显示什么。 | ||
| - %d是占位符，显示的时候，逗号后面的内容会替换%d。 | ||
|
|
||
| ## 三、变量存储 | ||
|
|
||
| ``` | ||
| #include <stdio.h> | ||
| int main() | ||
| { | ||
| int weight; //定义一个变量weight | ||
| weight = 170; //给weight赋值为170 | ||
| printf("%d\n",weight); //显示weight的值。 | ||
| weight = weight+10; | ||
| printf("%d\n",weight); | ||
| } | ||
| ``` | ||
|
|
||
| :::{figure-md} markdown-fig | ||
|  | ||
|
|
||
| 内存 | ||
| ::: | ||
|
|
||
|
|
||
| :::{figure-md} markdown-fig | ||
|  | ||
|
|
||
| 变量 | ||
| ::: | ||
|
|
||
| :::{figure-md} markdown-fig | ||
|  | ||
|
|
||
| 指针 | ||
| ::: |
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,169 @@ | ||
| --- | ||
| title: 关于Java类中数组对象创建的疑问 | ||
| date: 2019-01-11 21:04:05 | ||
| tags: | ||
| - java | ||
|
|
||
| categories: Java | ||
| --- | ||
|
|
||
|
|
||
| --- | ||
| # 关于Java类中数组对象创建的疑问 | ||
|
|
||
|
|
||
|
|
||
| ```java | ||
| public class Mix4{ | ||
| int counter = 0; | ||
| public static void main(String[] args){ | ||
| int count = 0; | ||
| Mix4 [] m4a = new Mix4[20]; | ||
| int x = 0; | ||
| while(x<9){ | ||
| m4a[x] = new Mix4(); | ||
| m4a[x].counter = m4a[x].counter + 1; | ||
| count = count + 1; | ||
| count = count + m4a[x].maybeNew(x); | ||
| x = x + 1; | ||
| } | ||
| System.out.println(count+" "+m4a[1].counter); | ||
| } | ||
|
|
||
| public int maybeNew(int index){ | ||
| if(index<5){ | ||
| Mix4 m4 = new Mix4(); | ||
| m4.counter = m4.counter + 1; | ||
| return 1; | ||
| } | ||
| return 0; | ||
| } | ||
|
|
||
| } | ||
| ``` | ||
| 这是Head First Java 中的一个习题， 在解答的过程中发现自己不了解以下几个知识点： | ||
|
|
||
| - 类实例变量的初始化 | ||
| - 数组对象的创建 | ||
|
|
||
| 对于第一个问题，**类实例变量的初始化**，在可视化的过程中我有了新的理解，先放上整个过程的结果。 | ||
|  | ||
|
|
||
| 下面写下我在执行这个程序中遇到并解决的一些问题 | ||
| 1. **程序是从main()开始的** | ||
| （这点我之前一直默认自己知道，但是程序真正执行起来，才发觉自己对这点的疏忽，还是需要谦虚些，默认自己什么都不知道，每个点都要踏踏实实扣下去） | ||
|  | ||
|
|
||
| 2. **数组是一个对象**， 无论被声明来承载的是primitive主类型数据或对象引用，数组永远是对象。 | ||
| 数组对象可以有primitive主数据类型的元素，但数组本身绝对不会是primitive主数据类型， 不管数组带有什么， 它一定是对象。 | ||
|
|
||
|
|
||
|
|
||
| 这句话的理解，在我看来可以这样解释： | ||
|  | ||
|
|
||
|
|
||
|
|
||
| ``` | ||
| Mix4 [] m4a = new Mix4[20]; | ||
| ``` | ||
|
|
||
| 这段程序可以分为三部分 | ||
| 1. 对象的声明 | ||
| 2. 对象的创建 | ||
| 3. 赋值 | ||
|
|
||
| - 对象的声明 | ||
|
|
||
| ``` | ||
| Mix4[] m4a | ||
| ``` | ||
|
|
||
| 声明了一个**类型**为Mix4[]的**数组变量**， 它的名称是m4a. | ||
|
|
||
| 这里补充一下，java注重类型， 声明变量必须有类型和名称（variables must have a type, variables must have a name） | ||
|
|
||
| to be continued.... | ||
|
|
||
| - 对象的创建 | ||
|
|
||
| ``` | ||
| new Mix4[20] | ||
| ``` | ||
| 创建大小为20的数组(这有着20个存储空间整体，为一个Mix4数组对象） | ||
| 而这20个存储空间可以用来存储类型为Mix4的对象 | ||
|
|
||
| 这里只保存着Mix4的引用 | ||
| 相当于只声明了对象,没有创建实际的Mix4对象。 | ||
| >可以这么理解 | ||
| ``` | ||
| Mix4 m4a[0]; | ||
| ``` | ||
| >数组中第一个索引里存放的是Mix4的引用 | ||
| >要创建Mix4对象的话 还要 | ||
| ``` | ||
| m4a[0] = new Mix4(); | ||
| ``` | ||
|
|
||
| - 赋值 | ||
| 连接对象和引用， 将Mix4[20]这个大小为20的数组，赋值给之前声明为Mix4[]的数组变量m4a. | ||
|
|
||
|  | ||
| 从上图中， 我们看到m4a这个数组变量，相当于一个遥控器，它指向了数组对象（也就是Mix4[20]），这个数组变量也称引用变量。 | ||
|
|
||
| 我们可以把变量看做杯子，变量用来装东西，也就是往杯子中装东西。 | ||
| 比如： | ||
| ``` | ||
| bype x = 7; | ||
| ``` | ||
| 就是代表数值7的字节（00000111）被放进变量中。 | ||
|
|
||
| 只不过这个引用变量装的东西比较特别，它放的东西代表**取得Mix4[20]对象的方法**以字节形式放进变量中，也就相当于一个遥控器， 这个引用变量可以通过 圆点“.”运算符来引用对象的方法和实例变量。 | ||
|
|
||
| 在数组中，对数组的操作可以不需要变量名称。只需要数组索引（位置）就可以操作特定对象： | ||
| ``` | ||
| Mix4 [] m4a = new Mix4[20]; | ||
| m4a[0] = new Mix4(); | ||
| m4a[0].counter = m4a[0].counter + 1; | ||
| ``` | ||
| 这段代码代表了程序第一次执行while循环时，x=0情况下，Mix4数组变量m4a[0]对Mix4对象的操作。 | ||
|  | ||
| 注意： | ||
| Mix4[20]数组中存放的仅仅是对Mix对象的引用， 还需要创建实际的Mix对象 | ||
|
|
||
| ``` | ||
| new Mix4() | ||
| ``` | ||
| ，并把它赋值给数组的元素 | ||
| ``` | ||
| m4a[0] = new Mix4() | ||
| ``` | ||
|
|
||
| 我理解错误的点主要在于对类实例变量的理解。 | ||
| 我把实例变量counter看做每个对象都可以进行修改的值，错误的把counter进行了累加。 | ||
|
|
||
| 实际上，每个类是对象的蓝图。 创建一个对象就是对类的实例化。 这个对象会有自己的实例变量和方法。 | ||
|
|
||
| 对象本身一致的事物被称为：实例变量（instance variable） | ||
| 对象可以执行的动作称为：方法（methods） | ||
|  | ||
| 可以看到程序进行到第8行时，new Mix4()创建了一个Mix4类型的对象， 它执行了两次初始化\<init:2>, 并且这个对象根据Mix4这个类的蓝图， 初始化了自己的实例变量counter = 0. | ||
|
|
||
| 之后将这个初始化了的对象赋值给了引用变量m4a[0] | ||
|  | ||
|
|
||
| 所以每一个数组引用变量都会有一个Mix4对象， 这些对象虽然是同一个类， 但每个都有自己独立的实例变量， 也就是counter. 而这个counter在创建对象时都会被赋值为0. | ||
|
|
||
|  | ||
|
|
||
| ``` | ||
| Mix4 [] m4a = new Mix4[20]; | ||
| m4a[x] = new Mix4(); | ||
| m4a[x].counter = m4a[x].counter + 1; | ||
| ``` | ||
| 现在重看这行代码， 你是否能有新的理解呢 | ||
|
|
||
| --- | ||
|
|
||
| 如有错误地方，请大家指正。 | ||
| 共同学习，共同进步，期待大家的issue~ |
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,11 @@ | ||
| --- | ||
| title: Java Design Pattern | ||
|
|
||
| --- | ||
|
|
||
| # Java Design Pattern | ||
|
|
||
| ### To be continue... | ||
|
|
||
| 单例模式： | ||
| 只有一个对象 |
Oops, something went wrong.