Reference Links: https://www.cnblogs.com/qing-gee/p/12090216.html
In java-based learning stuff about the length of three length length () size () can easily be confused
length String class () method represents the length of the string
ArrayList class size () method represented by a set of length
Then the length Where is it ??? no matter what type of array can be defined by the length property
length represents the length of the array
As a superclass (God class) Objdect also no length property
This property jdk length of the various data types in the source code are directly or indirectly points to the class String char value []
