java stringbuffer vs string

Question

can someone plz explain how the following code is being working:::
public class ConcatTest{
public static String concatWithString() {
String t = "Java";
for (int i=0; i<10000; i++){
t = t + "Tpoint";
}
return t;
}
public static String concatWithStringBuffer(){
StringBuffer sb = new StringBuffer("Java");
for (int i=0; i<10000; i++){
sb.append("Tpoint");
}
return sb.toString();
}
public static void main(String[] args){
long startTime = System.currentTimeMillis();
concatWithString();
System.out.println("Time taken by Concating with String: "+(System.currentTimeMillis()-startTime)+"ms");
startTime = System.currentTimeMillis();
concatWithStringBuffer();
System.out.println("Time taken by Concating with StringBuffer: "+(System.currentTimeMillis()-startTime)+"ms");
}
}

output is:
Time taken by Concating with String: 578ms
Time taken by Concating with StringBuffer: 0ms

Answer 1

but 0 ms in string buffer.,,, how could this even possible

Answer 2

this code show you if you use String Buffer to add line's for your String ,it is faster than String sorry for my bad English i cant explain in English very much

Answer 3

in nanosecond this is possible

Answer 4

Hi,
It's possible. String is immutable, so whenever you try to add a string it creates a new instance which takes time whereas StringBuffer is mutable and consumes less memory. This is why StringBuffer is faster and String is slower.