Java学习 day05

雨点打透心脏的1/2处 2021-11-24 00:08 273阅读 0赞

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1 异常  
1.1 概述：程序中出现不正常的情况

1.2 异常的由来：程序在运行时出现了不正常的情况，java提取了对应的属性、名字、原因等，形成了异常对象，进而形成了各种的异常类

1.3 异常的分类  
1.3.1 Error：(错误):运行中出现的严重错误,不需要我们进行更改

1.3.2 Exception：运行中出现的不严重的错误,我们可以尝试去更改

1.4 Exception的分类  
![20190727194239707.png][]

1.5 特点  
异常一旦发生，程序立即中断，所以当有多个异常的时候，默认只能执行第一个

1.6 try catch单异常处理  
![20190727100555702.png][]  
1.7 try catch多异常处理  
![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0JsZXNzaW5nWFJZ_size_16_color_FFFFFF_t_70 1][]  
1.8 try catch finally  
![20190727101827195.png][]  
![20190727102028554.png][]  
1.9 自定义异常  
1.9.1 概述  
![20190727195750917.png][]  
1.9.2 分类  
![20190727195836154.png][]  
1.9.3 常见的自定义异常  
1.9.3.1 订单异常

1.9.3.2 用户异常

1.9.3.3 负数异常  
![20190727195958763.png][]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0JsZXNzaW5nWFJZ_size_16_color_FFFFFF_t_70 2][]  
建议：调用方法的位置处理异常

2 模板设计模式  
2.1 概述  
![20190727200437544.png][]  
2.2 【样例】  
![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0JsZXNzaW5nWFJZ_size_16_color_FFFFFF_t_70 3][]

3 包装类  
3.1 概述：专门将简单数据类型的数据进行封装，形成的对应的类  
![20190727200717303.png][]  
3.2 常用方法  
![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0JsZXNzaW5nWFJZ_size_16_color_FFFFFF_t_70 4][]  
3.3 拆箱、装箱  
拆箱：从包装类对象中取出简单数据类型数据的过程  
装箱：将数据装入对应的包装类对象的过程  
![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0JsZXNzaW5nWFJZ_size_16_color_FFFFFF_t_70 5][]

4 枚举  
![20190727201156206.png][]  
5 BigInteger、BigDecimal  
5.1 BigInteger  
![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0JsZXNzaW5nWFJZ_size_16_color_FFFFFF_t_70 6][]  
5.2 BigDecimal  
![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0JsZXNzaW5nWFJZ_size_16_color_FFFFFF_t_70 7][]  
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6 Math、Date  
![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0JsZXNzaW5nWFJZ_size_16_color_FFFFFF_t_70 10][]

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[20190727194239707.png]: /images/20211122/1cdf4d84a5034cc484f6c82650adb500.png
[20190727100555702.png]: /images/20211122/27d2683ae24d4542b74c45ab4f443781.png
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[20190727101827195.png]: /images/20211122/177bdcd21e5e4b758cd80244b10dadf0.png
[20190727102028554.png]: /images/20211122/39bbd96ad73d4eac91a4f79e263853cc.png
[20190727195750917.png]: /images/20211122/f07b3a5d68cc4cb6bdcbfb2fa3572448.png
[20190727195836154.png]: /images/20211122/29f82d01528f414a850676949b742252.png
[20190727195958763.png]: /images/20211122/39e6dcdaf1b64aac9c9efaf6b003c0e6.png
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[20190727200437544.png]: /images/20211122/a35aff445b3146d09c5f34a4007d22c7.png
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[20190727200717303.png]: /images/20211122/300015d49b234d488858ee48459d5d34.png
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[20190727201156206.png]: /images/20211122/6010695e0d5445d090a8c68e32c2e8b4.png
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