JAVA 第三天

## 1.4流程控制学习

### 1.4.1用户交互Scanner

![image-20210204011916941](C:\Users\hp\AppData\Roaming\Typora\typora-user-images\image-20210204011916941.png)

![image-20210207014429857](C:\Users\hp\AppData\Roaming\Typora\typora-user-images\image-20210207014429857.png)

照着教程打了一段代码但不是很理解是什么意思

![image-20210207015219898](C:\Users\hp\AppData\Roaming\Typora\typora-user-images\image-20210207015219898.png)

就是跟Python的输入输出差不多吧，但是我觉得这个语法不够简洁很繁琐。

![image-20210207015619992](C:\Users\hp\AppData\Roaming\Typora\typora-user-images\image-20210207015619992.png)

果然可以简化成上图，不需要if

![image-20210207015527022](C:\Users\hp\AppData\Roaming\Typora\typora-user-images\image-20210207015527022.png)



### 1.4.2 Scanner进阶

![image-20210207020238835](C:\Users\hp\AppData\Roaming\Typora\typora-user-images\image-20210207020238835.png)

这个是标准格式先把这个写好防止以后忘。

![image-20210207020557893](C:\Users\hp\AppData\Roaming\Typora\typora-user-images\image-20210207020557893.png)

这个挺好理解的

![image-20210207021126153](C:\Users\hp\AppData\Roaming\Typora\typora-user-images\image-20210207021126153.png)

是一个计算，不知道为什么java奇慢无比，可能是安到d盘的原因吗？



### 1.4.3顺序结构

![image-20210207021417585](C:\Users\hp\AppData\Roaming\Typora\typora-user-images\image-20210207021417585.png)

### 1.4.4 if结构

![image-20210207021612425](C:\Users\hp\AppData\Roaming\Typora\typora-user-images\image-20210207021612425.png)

![image-20210207022152754](C:\Users\hp\AppData\Roaming\Typora\typora-user-images\image-20210207022152754.png)

这没啥好说的，一个判断

![image-20210207022242334](C:\Users\hp\AppData\Roaming\Typora\typora-user-images\image-20210207022242334.png)

![image-20210207022420102](C:\Users\hp\AppData\Roaming\Typora\typora-user-images\image-20210207022420102.png)

![image-20210207022637344](C:\Users\hp\AppData\Roaming\Typora\typora-user-images\image-20210207022637344.png)



### 1.4.5 Swith选择结构

![image-20210207022806471](C:\Users\hp\AppData\Roaming\Typora\typora-user-images\image-20210207022806471.png)

case穿透现象：如果没有break会继续执行之后的，所以每写一个case就应该写一个break

switch是匹配，if是判断

这节课讲了反编译

看源码是好程序员必备的思想

### 1.4.6 While循环

![image-20210207023821313](C:\Users\hp\AppData\Roaming\Typora\typora-user-images\image-20210207023821313.png)

![image-20210207023905129](C:\Users\hp\AppData\Roaming\Typora\typora-user-images\image-20210207023905129.png)

![image-20210207024111769](C:\Users\hp\AppData\Roaming\Typora\typora-user-images\image-20210207024111769.png)

死循环：一直需要循环，一般情况需要避免，抢票用

### 1.4.7 DoWhile循环

![image-20210207024304809](C:\Users\hp\AppData\Roaming\Typora\typora-user-images\image-20210207024304809.png)

需求：不满足循环也要至少执行一次

### 1.4.8 for循环——让循环结构更简单

![image-20210207024507839](C:\Users\hp\AppData\Roaming\Typora\typora-user-images\image-20210207024507839.png)

![image-20210207024625850](C:\Users\hp\AppData\Roaming\Typora\typora-user-images\image-20210207024625850.png)

果然很高效！！！

缩写：100.for——自动生成

![image-20210207024743298](C:\Users\hp\AppData\Roaming\Typora\typora-user-images\image-20210207024743298.png)

![image-20210207025146377](C:\Users\hp\AppData\Roaming\Typora\typora-user-images\image-20210207025146377.png)

每三个换行

### 1.4.9 打印99乘法表

![image-20210207025500365](C:\Users\hp\AppData\Roaming\Typora\typora-user-images\image-20210207025500365.png)

把目标分步:拆分成小问题由易到难，解决复杂问题

### 1.4.10 增强for循环——数组用

![image-20210207025602575](C:\Users\hp\AppData\Roaming\Typora\typora-user-images\image-20210207025602575.png)

![image-20210207025713623](C:\Users\hp\AppData\Roaming\Typora\typora-user-images\image-20210207025713623.png)

历遍了数组

### 1.4.11 break continue

![image-20210207025932781](C:\Users\hp\AppData\Roaming\Typora\typora-user-images\image-20210207025932781.png)

![image-20210207030004080](C:\Users\hp\AppData\Roaming\Typora\typora-user-images\image-20210207030004080.png)

用continue可以跳过一些东西

### 1.4.12打印三角形+Debug

![image-20210207030536732](C:\Users\hp\AppData\Roaming\Typora\typora-user-images\image-20210207030536732.png)

![image-20210207030633592](C:\Users\hp\AppData\Roaming\Typora\typora-user-images\image-20210207030633592.png)

debug：可以看程序怎么执行的

posted @ 2021-02-07 03:10  柒汾  阅读(33)  评论(0)    收藏  举报