The method of judging the same variable without the if branch

For the problem of using the same variable for multiple conditions, taking equal judgment

if a == 1else if a == 2else if a == 3

First of all, to optimize the look and feel, it is better to convert magic numbers such as 1, 2, 3 into enumeration types and use meaningful names to standardize them, rather than using magic numbers directlymany.

Secondly, to optimize the performance, change the multi-if branch to the hash method, for example, use a hashmap key to store all 1, 2, 3, change 1,2, 3 The functions executed by , write three functions respectively, store the objects of these three functions in the value of the hashmap, and establish a mapping.

Many software projects like to use this design method,
but this method also has limitations in many cases, maybe the final performance optimization is just self-deception,
discrete function executionAt the same time, it also causes the distribution of functions in memory to be more discrete. In the case of a large amount of functions, it may lead to CPU Cache Miss, which needs to be read into the paging from the memory again, resulting in entering the operating system kernel state