ScopeTest.java

Download this source file

// Scope and Lifetime Quiz.  What is the expected output of this program?
//
// Written 2001 by Wayne Pollock, Tampa Florida USA.

class ScopeTest
{
   public static void main ( String [] args )
   {
      for ( int i = 0; i < 10; ++i )
      {  int j = 2;
         ++j;
         System.out.println( j );
      }
   }
}

See the Answer

Answer

In this program, the local variable j has the same scope as i (the body of the for loop) but a different lifetime.  i comes into existance at the begining of the for loop, and goes away only when the loop exits.  In contrast, j comes into existence and goes away each iteration of the loop.  The program below thus prints out ten "3"s, not "3 4 5 6 7 8 9 10 11 12".

Send comments and questions to pollock@acm.org.