74 lines
1.3 KiB
Markdown
74 lines
1.3 KiB
Markdown
- [[StringBuilder]]
|
|
- [[StringBuffer]]
|
|
- [[Arrays]]
|
|
- [[System]]
|
|
- [[Runtime]]
|
|
- [[Math]]
|
|
- [[Random]]
|
|
- [[UUID]]
|
|
- [[BigDecimal]]
|
|
-
|
|
-
|
|
- 总结
|
|
collapsed:: true
|
|
- StringBuilder
|
|
- 长度，内容可变的字符串
|
|
- 常用API
|
|
- append
|
|
- insert
|
|
- capacity
|
|
- length
|
|
- setCharAt
|
|
- deleteCharAt
|
|
- delete
|
|
- reverse
|
|
- substring
|
|
- indexOf
|
|
- lastIndexOf
|
|
- StringBuffer
|
|
- 所有API及操作与StringBuilder一致
|
|
- Arrays
|
|
- toString
|
|
- sort
|
|
- binarySearch
|
|
- copyOf
|
|
- equals
|
|
- System
|
|
- exit
|
|
- gc
|
|
- currentTimeMillis
|
|
- nanoTime
|
|
- arraycopy
|
|
- getProperties
|
|
- Runtime
|
|
- Math
|
|
- random
|
|
- abs
|
|
- pow
|
|
- max
|
|
- min
|
|
- round
|
|
- Random
|
|
- ```java
|
|
Random a = new Random();
|
|
```
|
|
- 回溯历史
|
|
- Random(long seed)
|
|
- {{embed [[UUID]]}}
|
|
- BigDecimal
|
|
- 解决浮点数精度丢失的问题
|
|
- 使用字符串作为参数最精准
|
|
- 加减乘除
|
|
- add
|
|
- subtract
|
|
- multiply
|
|
- divide
|
|
- 除法除不尽
|
|
- 收尾
|
|
- ROUND_DOWN 去尾
|
|
- 只保留小数点后指定位数
|
|
- ROUND_UP 收尾
|
|
- 保留小数点后指定位数,如果保留位的后一位不为零,保留位的值加1
|
|
- ROUND_HALF_UP 四舍五入
|
|
- 保留小数点后指定位数,如果保留位的后一位<5,保留位数的值不加1,保留位的后一位>=5,保留位数的值加1
|
|
- |