There
are three Iteration statement in java. They are.....
- for
- while
- do-while
while
while
loop is the most fundamental loop statement in java. It repeats or
block while it's controlling expression is true. Here general form
while(condition){
//body
of loop
}
The
condition can be boolean expression. The body of the loop will
executed as long as the conditional expression is true. If the
condition becomes false, then control passes to the next line of code
immediately following the loop.
Example:
import
java.util.Scanner;
public
class
TestWhile {
public
static
void
main(String args[]){
Scanner
pavel = new
Scanner(System.in);
System.out.println("How
much do you want the loop execute from 0");
int
loop = pavel.nextInt();
int
x = 0;
while(x<=loop){
System.out.println("NUmber"+"\t"+x);
x++;
}
}
}
OUTPUT:
How
much do you want the loop execute from 0
5
NUmber 0
NUmber 1
NUmber 2
NUmber 3
NUmber 4
NUmber 5
Now
look here,we input 5 .then it output us o to 5.Because here x is
initialize as 0 and loop execute up to the x<=our inputed number.
In
the example initially x=0; when while loop execute first it see, is
(x<=loop) is true. Our input is 5.
so
loop =5.
Now
for x=0 0<=5 is true
So
execute the body statement .first found print statement so execute
Number 0
then
see increment statement x++
So
execute this. now x=0+1=1
Now
for x=1 1<=5 is true
So
execute the body statement .first found print statement so execute
Number 1
then
see increment statement x++
So
execute this. now x=1+1=2
…............................................................................................................................
….............................................................................................................................
….............................................................................................................................
Now
for x=5 5<=5 is true
So
execute the body statement .first found print statement so execute
Number 5
then
see increment statement x++
So
execute this. now x=5+1=6
Now
for x=6 6<=5 is false
So
loop end.
Some
times we think ,what will happen if we set increment statement in the
top of the statement ….now we will see that
import
java.util.Scanner;
public
class
TestWhile {
public
static
void
main(String args[]){
Scanner
pavel = new
Scanner(System.in);
System.out.println("How
much do you want the loop execute from 0");
int
loop = pavel.nextInt();
int
x = 0;
while(x<=loop){
x++;
System.out.println("NUmber"+"\t"+x);
}
}
}
OUTPUT:
How
much do you want the loop execute from 0
5
NUmber 1
NUmber 2
NUmber 3
NUmber 4
NUmber 5
NUmber 6
Now
see here the same code only increment statement is in the top of the
while loop and input is same. But we see here we found a different
output. Now I will explain you that.
In
the this example also initially x=0; when while loop execute first
it see, is (x<=loop) is true. Our input is 5.
so
loop =5.
Now
for x=0 0<=5 is true
So
execute the body statement .First see increment statement x++
So
execute this. now x=0+1=1
Then
found print statement so execute Number 1
Now
for x=1 1<=5 is true
So
execute the body statement .First see increment statement x++
So
execute this. now x=1+1=2
then
found print statement so execute Number 2
…............................................................................................................................
….............................................................................................................................
….............................................................................................................................
Now
for x=5 5<=5 is true
So
execute the body statement .first see increment statement x++
So
execute this. now x=5+1=6
Then
found print statement so execute Number 6
Now
for x=6 6<=5 is false
So
loop end.
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