How many string objects - please suggest

Question

Hi there,
Can you somebody please tell how many String objects will be created when the following method is invoked?
public String makinStrings() {
String s = “Fred”;
s = s + “47”;
s = s.substring(2, 5);
s = s.toUpperCase();
return s.toString();
Thanks
Shan

Answer 1

Hi VShan,
This is your code
public String makinStrings() {
String s = “Fred”;     //1
s = s + “47”;            //2
s = s.substring(2, 5);//3
s = s.toUpperCase(); //4
return s.toString();     //5
EXPLANATION : String is an immutable object, that means the String object cannot change it's contents.It might sound very unfamiliar but it is TRUE. In line 1: You declare a String object by assigning a a String literal "Fred" to the variable s. Now when you concat "47" with the original contents of s , a new memory space is allocated where s is assigned.+It is important to note+ that the previous reference of s i.e. "Fred" will be lost and now s refers to a new memory location where the contents are "Fred47" , so you have created another object in Line 2. Similarly you create another object in line3 & 4.As far my calculations you have created 4 objects.
I would like you to kindly note that s is already a String so you can directly return s and hence there is no need of s.toString() in Line 5.You should also note that each object is also an eligible candidate for Grabage Collection.
So as soon as Line2 gets executed , the object in Line1 becomes eligible for garbage collection.. that means when GC runs that object will be reclaimed and hence memory will be freed.