References
Where are static methods and static variables stored in Java?
Static class in Java
CPU
Branch prediction:
Why is processing a sorted array faster than processing an unsorted array?
Branch predictor
提前 if 判断帮助 CPU 分支预测
ChannelEventRunnable.java
Object
create object
Different ways to create objects in Java
Creating New Class Instances
Playing with constructors
hashCode
关于 public native int hashCode() 方法的实现可以参考 Serializable
clone
Deep, Shallow and Lazy Copy with Java Examples
OOPs
JLS
MySQL
NULL
- Conceptually, NULL means “a missing unknown value” and it is treated somewhat differently from other values.
- In SQL, the NULL value is never true in comparison to any other value, even NULL. An expression that contains NULL always produces a NULL value unless otherwise indicated in the documentation for the operators and functions involved in the expression.
- You can add an index on a column that can have NULL values if you are using the MyISAM, InnoDB, or MEMORY storage engine. Otherwise, you must declare an indexed column NOT NULL, and you cannot insert NULL into the column.
- When using DISTINCT, GROUP BY, or ORDER BY, all NULL values are regarded as equal.