do while and while

[M Rama]

Again from k&b, this example has me confused:

 
 
int i =1;
do while ( i<1)
System.out.println("i is "+i);
while(i>1);
 
 

k&b says that in the above code it is two independent loops. one is do while and the other is while.

but, when i delete the last line "while(i>1)" and compile, my compiler doesn't like it. how does this work?

also, i thought, for do...while the statements if any, would be inbetween do and while. ex:

int i = 15;
do
System.out.println("i is "+ i--);
while(i>10);
 
  

[Animesh Shrivastava]

It means that,
look below at the code

  
int i =1;
do // Do-while loop starts here
 
  while ( i<1) // Just a while statement
   System.out.println("i is "+i); 
 
while(i>1);// D-While loop ends here

Now if u remove the last while, which means ur do-while doesnt terminate properly.

  
int i =1;
do // Do-while loop starts here
 
  while ( i<1) // Just a while statement
   System.out.println("i is "+i); 
 
// Where does while end???
 

[Raghu Shree]

Hi,
You expect lot of question like this in certification Exam. If curly braces are not in while loop it executes only next line of the while loop.
for example

 
  do
   {
     while (i<10)
      {
        System.out.println ("hai");
      }
   }while (j<10);   

if curly braces are not placed in above code it work like above.
[ April 06, 2005: Message edited by: Raghu Shree ]

[Shivakanth Thyagarajan]

Hi Animesh,
public static void main( String args[] ) {
int i = 1 ;
do
while( i < 15 )
System.out.println( "Ok" ) ;
while( i < 1 );
}
}

No if the above code is modified in this manner

public static void main( String args[] ) {
int i = 1 ;
do
while( i < 15 ) ;
System.out.println( "Ok" ) ;
//while( i < 1 );
}
}

It's throwing up an error, "while expected",

Does this convey to us that b/w do and while an statement should exist else compiler will throw up an error.

[Animesh Shrivastava]

Yeah there has to be a loop body or statement in between Do-While.

  
 do {
 }while ( i<1);

The above code also works, even though there is no statement inside the loop body,

also, this works:

  
do 
  System.out.println("");
while ( i<1);

Here just a statement is described

[M Rama]

Wow!! Great explanations. Thanks so much guys.

[Parameswaran Thangavel]

hi

do
while( i < 15 ) //always true
System.out.println( "Ok" ) ;
while( i < 1 );


isn't this result in infinite loop.

[Animesh Shrivastava]

Indeed its an infinite loop and the jvm will go just running it forever.
Well, about its being unreachable there is a JLS topic u can go thru it.
unreachable
Well,
Its quite confusing and questions related to these topics usually dont come. Well i havent given the exam so i cant say u exactly whether such questions come or not.
So i suggest u can just skip ths topic.

U can go thru this thread for more info
unreachable