Understanding and verification of null value in java

Understanding and verification of null value in java

    The understanding of non-empty and null in the back-end parameters of the purpose has been fuzzy, resulting in always some problems in understanding. Combined with the online statement, I have verified the cognition on my own side.

Landing
    on the basic data types, reference data types (normal object, String objects, an array of objects, List object Map object) validation and summary.

Summarize the
    basic data types-there is no such
    thing as null , ordinary objects-null is null,
    array, String, List, Map-null means that this object does not have, and null means the number of elements in this object Is 0, and the existence of the object is a prerequisite to verify that it is not empty,