Java学习 day03

灰太狼 2021-11-26 14:18 289阅读 0赞

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0JsZXNzaW5nWFJZ_size_16_color_FFFFFF_t_70][]  
1 JVM的优化

2 数组  
2.1 基础理解：  
![20190724095910893.png][]  
2.2 创建数组：  
![20190724100549890.png][]  
创建数组并初始化  
![20190724103017409.png][]  
2.3 数组赋值  
![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0JsZXNzaW5nWFJZ_size_16_color_FFFFFF_t_70 1][]  
2.4 数组遍历  
![20190724103115350.png][]  
2.5 数组应用  
![2019072410332643.png][]  
2.6 异常报错  
![20190724103221917.png][]  
3 二维数组  
3.1 理解：特殊的一维数组，其中的每个元素都是一个一维数组  
![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0JsZXNzaW5nWFJZ_size_16_color_FFFFFF_t_70 2][]  
3.2 动态初始化  
![截图来源于菜鸟教程][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0JsZXNzaW5nWFJZ_size_16_color_FFFFFF_t_70 3]  
3.3 创建数组、赋值  
![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0JsZXNzaW5nWFJZ_size_16_color_FFFFFF_t_70 4][]  
![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0JsZXNzaW5nWFJZ_size_16_color_FFFFFF_t_70 5][]  
3.4 数组遍历  
![20190724112820561.png][]

4 【比较】简单数据类型、引用数据类型  
![20190724095937584.png][]  
5 值传递、址传递  
![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0JsZXNzaW5nWFJZ_size_16_color_FFFFFF_t_70 6][]  
![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0JsZXNzaW5nWFJZ_size_16_color_FFFFFF_t_70 7][]  
址传递关键点：是否让两个引用指向一个数组（堆中的地址）

6 排序算法  
6.1 概述  
![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0JsZXNzaW5nWFJZ_size_16_color_FFFFFF_t_70 8][]  
6.2 时间复杂度  
![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0JsZXNzaW5nWFJZ_size_16_color_FFFFFF_t_70 9][]  
![20190724114422897.png][]  
6.3 冒泡排序  
![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0JsZXNzaW5nWFJZ_size_16_color_FFFFFF_t_70 10][]  
![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0JsZXNzaW5nWFJZ_size_16_color_FFFFFF_t_70 11][]  
6.4 选择排序  
![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0JsZXNzaW5nWFJZ_size_16_color_FFFFFF_t_70 12][]  
![20190724120900149.png][]  
7 查找算法  
7.1 二分查找  
![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0JsZXNzaW5nWFJZ_size_16_color_FFFFFF_t_70 13][]  
![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0JsZXNzaW5nWFJZ_size_16_color_FFFFFF_t_70 14][]  
关键点：数组必须是有序的

8 面向对象  
8.1 概述  
![20190724142356869.png][]  
8.2 理解面向对象  
![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0JsZXNzaW5nWFJZ_size_16_color_FFFFFF_t_70 15][]  
8.3 面向对象的特点  
![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0JsZXNzaW5nWFJZ_size_16_color_FFFFFF_t_70 16][]  
9.1 类的定义  
![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0JsZXNzaW5nWFJZ_size_16_color_FFFFFF_t_70 17][]  
![20190724152434737.png][]  
10 对象  
10.1 创建对象  
![20190724150359523.png][]  
10.2 对象的内存  
![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0JsZXNzaW5nWFJZ_size_16_color_FFFFFF_t_70 18][]  
10.3 多引用指向同一对象  
![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0JsZXNzaW5nWFJZ_size_16_color_FFFFFF_t_70 19][]  
10.4 有名对象、匿名对象  
![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0JsZXNzaW5nWFJZ_size_16_color_FFFFFF_t_70 20][]  
匿名对象作用：创建一个对象，只用一次

10.5 成员变量  
静态成员变量：static修饰，通常使用类名调用  
非静态成员变量：不使用static修饰，不能使用类名调用  
![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0JsZXNzaW5nWFJZ_size_16_color_FFFFFF_t_70 21][]  
![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0JsZXNzaW5nWFJZ_size_16_color_FFFFFF_t_70 22][]  
![20190724160650644.png][]  
10.6 构造方法  
![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0JsZXNzaW5nWFJZ_size_16_color_FFFFFF_t_70 23][]  
使用构造方法的注意点：  
![20190724161940690.png][]  
10.7 this关键字  
1 用来区分成员变量和局部变量  
2 可以在构造方法内部调用其它重载的构造方法  
![20190724163010412.png][]  
11 静态代码块、构造代码块  
![20190724163331868.png][]  
![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0JsZXNzaW5nWFJZ_size_16_color_FFFFFF_t_70 24][]  
输出：abcdedef

12 脏数据  
![20190724164236753.png][]  
13 抽象、封装、继承、多态  
13.1 抽象

13.2 封装  
![20190724164433386.png][]  
拓展：JavaBean

13.3 继承  
13.3.1 概述：  
![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0JsZXNzaW5nWFJZ_size_16_color_FFFFFF_t_70 25][]  
![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0JsZXNzaW5nWFJZ_size_16_color_FFFFFF_t_70 26][]  
![截图来源于菜鸟教程][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0JsZXNzaW5nWFJZ_size_16_color_FFFFFF_t_70 27]  
![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0JsZXNzaW5nWFJZ_size_16_color_FFFFFF_t_70 28][]  
![20190724170727365.png][]  
13.3.2 重写：  
![20190724165410993.png][]  
扩展：重写方法的返回值可以与父类的相同，也可以是父类返回值类型的子类  
13.3.3 【比较】this、super  
![20190724170639653.png][]

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