It was an interview question. I was asked to implement the StringBuffer append function. I saw the code after the interview. But I cannot understand how the operation is done with creation of a single object.
I am thinking like this.
String s = "orange";
s.append("apple");
Here two objects are created.
But
StringBuilder s = new StringBuilder("Orange");
s.append("apple");
Now here only one object is created.
How is Java doing this operation?
String is immutable. Appending a string can only generate a new string.
StringBuilder is mutable. Appending to a StringBuilder is an in-place operation, like adding to an ArrayList.
This doesn't compile.
String S= "orange";
S.append("apple");
if you do
final String S= "orange";
final S2 = S + "apple";
This doesn't create any objects as it is optimised at compile time to two String literals.
StringBuilder s = new StringBuilder("Orange");
s.append("apple");
This creates two objects StringBuilder and the char[] it wraps. If you use
String s2 = s.toString();
This creates two more objects.
If you do
String S= "orange";
S2 = S + "apple";
This is the same as
String S2 = new StringBuilder("orange").append("apple").toString();
which creates 2 + 2 = 4 objects.
StringBuilder is holding a buffer of chars in a char[] and converting them to a String when toString is called.
****String s1="Azad"; ----One object will create in String cons. pool
System.out.println(s1);--output--Azad
s1=s1.concat("Raja"); Two object will create 1-Raja,2-AzadRaja and address of AzadRaja Store in reference s1 and cancel ref.of Azad object
System.out.println(s1); --output AzadRaja****