Dan's Mock FLow Question

[Vidyavathi saravanan]

class JMM110 {
  public static void main (String[] args) {
    int j = 0;
    do for (int i = 0; i++ < 2; ) 
      System.out.print(i);
    while (j++ < 2);
}}
 

Answer options:
a. Prints: 0001
b. Prints: 012
c. Prints: 012012
d. Prints: 012345
e. Prints: 001122
f. Prints: 1112
g. Prints: 111222
h. Prints: 121212
i. Run-time error
j. Compile-time error
k. None of the above

Answer is h. Could anyone please explain this to me?

Thanks!

(got rid of smiley in code portion)
[ October 16, 2004: Message edited by: Barry Gaunt ]

[Barry Gaunt]

Let's rewrite this a little:

class JMM110 {
  public static void main (String[] args) {
    int j = 0;
    do
    {
       for (int i = 0; i++ < 2; )
       { 
          System.out.print(i);
       }
    }
    while (j++ < 2);
  }
}

This is entirely equivalent to the previous code. It maybe easier to analyze now.

[Peixiao Lin]

do{}while(A) loop will iterate one more time than while(A){} loop. so in this case, the inside for loop will iterate 3 times. For each inside for loop iteration, the output is 12, so the final output is 121212

[Vipin Das]

 
Hi,
  while analysing this code u should keep 3 pints in mind.
  1. In an expression a post increment operator will increment the variable after evaluating the exp.
  2. A do.. while loop can  execute a single statement with out opening or closing braces
  3. Any section of a for loop can be omitted.
  4. A loop can be considered as a single statement.
 
    Now some more tips:
     Use a paper and pencil and traverse the loops and note down the current values of the
variables when nested loops are involved.
     if the innermost loop is printing or doing something independently it will be printed the no: of times t
the outer loop executes.
 
    Keeping all these things in mind:
         
    I     First of all we will traverse the inner for loop. Its  iterating
          portion is mixed with the conditional portion.So there is no iteration part.
           Here the initial value of i = 0; In i++ < 2, it is postincrement, therefore o < 2 
           is checked. But when it comes to the next line to print the value of i will be 1.
           similarly it will print 12 in one complete execution.
     
    II    The outer while loop executes thrice in the same manner. Therefore 12 will be printed
          twice and hence the answer.