The toString method of the Object class

1. Print objects of other classes. If it is found to be an address value, then this class does not rewrite toString in the Object class, otherwise this class must be rewritten, toSrting
2. Objects.equals(s1,s2),
for two objects Compare to prevent null pointer exceptions.
3. Null is the default value of the reference data type.
4. The package is not required when using classes that are not under the lang package.