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Control Statements > Iteration statements (Loops) >
Siva Nookala - 12 Apr 2016
Although for and while are both loops, there are few differences in the syntax and the usage.

The major differences between for and while are:
  • for loop is used when we know the number of iterations we have to perform i.e. we know how many times we need to execute a loop.
  • while is used when you are not sure about the iterations but you know what the condition is and then you can loop that block until the condition is false.
  • Although for and while are different, every for loop can be rewritten using while and every while can be rewritten using for.
Below are few examples which are written using while and for.
Print numbers till given input using for
int input = 5;
for(int i = 1; i <= input; i++ )
{
    System.out.println(i);
}
The same program using while.
int input = 5;
int i = 1;
while(i <= input)
{
    System.out.println(i);
    i++;
}


Print numbers from given number till the next multiple of 10. e.g., if input is 5 it should print 5, 6, 7, 8, 9, 10 or if input is 27 it should print 27, 28, 29, 30 or if input is 40 then it should print 40.
This program written using for.
int input = 5;
for(int i = input; ( i == input || ((i - 1) % 10 != 0)); i++ )
{
    System.out.println(i);
}
Same program written using while.
int input = 5;
int i = input;
while(i == input || ((i - 1) % 10 != 0))
{
    System.out.println(i);
    i++;
}
Same program written using do-while.
int input = 5;
int i = input;
do
{
    System.out.println(i);
    i++;
}while(((i - 1)% 10 != 0));

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