System.out.err & System.out interleaving in Java -

to work out how time taken perform algorithm, in main method, not print time gets interleaved system.print.

 long starttime = system.currenttimemillis();      a1.print(2);  long endtime = system.currenttimemillis();  system.err.print(endtime - starttime); 

and if class this:

public class a{  public void print(int n){ for(int = 0; <=n; i++){ system.out.println(i) }} 

it prints

0

1

2

and in line amount of time supposed go through loop, won't, won't print this:

0

1

2

1

here last line or 1 millisecond taken algorithm. textbook says must use system.err. , figure out way prevent interleaving.

you like

system.seterr(system.out); 

so output in same stream. use 2 different streams that's why interleaving.

for code be:

long starttime = system.currenttimemillis();     system.seterr(system.out);  a1.print(50); long endtime = system.currenttimemillis(); system.err.print(endtime - starttime);