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?
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.