Some useful printf-style formats of java.util.Formatter

java.util.Formatter which is introduced in J2SE 5.0 provides an interpreter for printf-style format strings. You can use pritf-style format through java.io.PrintStream instance.

int n = 1000000;
long millis = System.currentTimeMillis();
theLongRunningFunction(n);
System.out.printf("%d items - %d msecs elapsed\n",
    n, System.currentTimeMillis() - millis);

// => 1000000 items - 164 msecs elapsed

The elapsed seconds is formatted by using %f conversion and precision specifier.

int n = 1000000;
long millis = System.currentTimeMillis();
theLongRunningFunction(n);
System.out.printf("%d items - %.2f secs elapsed\n",
    n, (System.currentTimeMillis() - millis)/1000.0);

// => 1000000 items - 0.16 secs elapsed

The locale-specific grouping separators is also supported.

int n = 1000000;
long millis = System.currentTimeMillis();
theLongRunningFunction(n);
System.out.printf("%,d items - %.2f secs elapsed\n",
    n, (System.currentTimeMillis() - millis)/1000.0);

// => 1,000,000 items - 0.16 secs elapsed