Difference between null and empty string

Question

What is the difference between a null string  String s   null  and an empty string  String s          This is what I have   String s1         print statement does not print any thing for s1 but s1 length   0 String s2   null   print statement prints  null  for s2  but s2 length   gives exception   What does it mean

User · Accepted Answer

String s1       means that the empty String is assigned to s1  In this case  s1 length   is the same as    length    which will yield 0 as expected         String s2   null  means that  null  or  no value at all  is assigned to s2   So this one  s2 length   is the same as null length    which will yield a NullPointerException as you can t call methods on null variables  pointers  sort of  in Java   Also  a point  the statement  String s1    Actually has the same effect as   String s1   null    Whereas  String s1         Is  as said  a different thing

User · Answer

When Object variables are initially used in a language like Java  they have absolutely no value at all - not zero  but literally no value - that is null  For instance  String s   If you were to use s  it would actually have a value of null  because it holds absolute nothing   An empty string  however  is a value - it is a string of no characters   String s    Inits to null String a        A blank string   Null is essentially  nothing  - it s the default  value   to use the term loosely  that Java assigns to any Object variable that was not initialized   Null isn t really a value - and as such  doesn t have properties  So  calling anything that is meant to return a value - such as  length    will invariably return an error  because  nothing  cannot have properties   To go into more depth  by creating s1       you are initializing an object  which can have properties  and takes up relevant space in memory   By using s2  you are designating that variable name to be a String  but are not actually assigning any value at that point

User · Answer

Null means nothing  Its just a literal  Null is the value of reference variable  But empty string is blank It gives the length 0  Empty string is a blank value means the string does not have any thing

User · Answer

No method can be invoked on a object which is assigned a NULL value  It will give a nullPointerException  Hence  s2 length   is giving an exception

[java] Difference between null and empty string

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