for loop in java
By: Abinaya
Here is the general form of the for statement:for(initialization; condition; iteration) {
// body
}
If only one statement is being repeated, there is no need for the curly braces.
The for loop operates as follows. When the loop first
starts, the initialization portion of the loop is executed. Generally, this is an expression that sets the
value of the loop control variable, which acts as a counter that controls the loop. It
is important to understand that the initialization expression is only executed once. Next, condition
is evaluated. This must be a Boolean expression. It usually tests the loop control
variable against a target value. If this expression is true, then the body of the loop is
executed. If it is false, the loop terminates. Next, the iteration portion of the loop is
executed. This is usually an expression that increments or decrements the loop control
variable. The loop then
iterates, first evaluating the conditional expression, then
executing the body of the loop, and then executing the iteration expression with each pass. This
process repeats until the controlling expression is false. Here is a version of the "tick" program that uses a for
loop:
// Demonstrate the for loop.
class ForTick {
public static void main(String args[]) {
int n;
for(n=10; n>0; n--)
System.out.println("tick " + n);
}
}
Declaring Loop Control Variables Inside the for Loop
Often the variable that controls a for loop is only
needed for the purposes of the loop and is not used elsewhere. When this is the case, it is possible to
declare the variable inside the initialization portion of the for. For example, here
is the preceding program recoded so that the loop control variable n is declared as an int
inside the for:
// Declare a loop control variable inside the for.
class ForTick {
public static void main(String args[]) {
// here, n is declared inside of the for loop
for(int n=10; n>0; n—)
System.out.println("tick " + n);
}
}
When you declare a variable inside a for loop, there is one important point to remember: the scope of that variable ends when the for statement does. (That is, the scope of the variable is limited to the for loop.) Outside the for loop, the variable will cease to exist. If you need to use the loop control variable elsewhere in your program, you will not be able to declare it inside the for loop. When the loop control variable will not be needed elsewhere, most Java programmers declare it inside the for. For example, here is a simple program that tests for prime numbers. Notice that the loop control variable, i, is declared inside the for since it is not needed elsewhere.
// Test for primes.
class FindPrime {
public static void main(String args[]) {
int num;
boolean isPrime = true;
num = 14;
for(int i=2; i < num/2; i++) {
if((num % i) == 0) {
isPrime = false;
break;
}
}
if(isPrime) System.out.println("Prime");
else System.out.println("Not Prime");
}
}
Using the Comma
There will be times when you will want to include more than one statement in the initialization and iteration portions of the for loop. For example, consider the loop in the following program:
class Sample {
public static void main(String args[]) {
int a, b;
b = 4;
for(a=1; a<b; a++) {
System.out.println("a = " + a);
System.out.println("b = " + b);
b—;
}
}
}
As you can see, the loop is controlled by the interaction of two
variables. Since the loop is governed by two variables, it would be useful if both could be
included in the for
statement, itself, instead of b being handled manually.
Fortunately, Java provides a way to accomplish this. To allow two or more variables to control a for
loop, Java permits you to include multiple statements in both the initialization and
iteration portions of the for. Each statement is separated from the next by a comma.
Using the comma, the preceding for loop can be more
efficiently coded as shown here:
// Using the comma.
class Comma {
public static void main(String args[]) {
int a, b;
for(a=1, b=4; a<b; a++, b—) {
System.out.println("a = " + a);
System.out.println("b = " + b);
}
}
}
In this example, the initialization portion sets the values of both a and b. The two comma separated statements in the iteration portion are executed each time the loop repeats.
The program generates the following output:
a = 1
b = 4
a = 2
b = 3
Note : If you are familiar with C/C++, then you know that in those languages the comma is an operator that can be used in any valid expression. However, this is not the case with Java. In Java, the comma is a separator that applies only to the for loop.
Archived Comments
1. uhetuzoeyiwa
View Tutorial By: uhetuzoeyiwa at 2017-09-20 01:08:46
2. hi sir can you help me with this problem
3. Formulate program SumNumbers that comput
View Tutorial By: Lee at 2015-10-01 09:08:26
3. sir i want this following pattern using loops
**********
*******
*****
View Tutorial By: teju at 2015-09-13 22:46:58
4. sir, i want if,if else,nested if..... concept in one(same) program...........
View Tutorial By: krishna at 2015-08-14 08:58:01
5. sir, i want if,if else,nested if..... concept in one(same) program...........
View Tutorial By: krishna at 2015-08-14 08:57:23
6. sir, i want if,if else,nested if..... concept in one(same) program...........
View Tutorial By: krishna at 2015-08-14 08:55:48
7. sir, i want if,if else,nested if..... concept in one(same) program...........
View Tutorial By: krishna at 2015-08-14 08:55:25
8. sir, i want if,if else,nested if..... concept in one(same) program...........
View Tutorial By: krishna at 2015-08-14 08:54:53
9. sir, i want if,if else,nested if..... concept in one(same) program...........
View Tutorial By: krishna at 2015-08-14 08:54:43
10. sir, i want if,if else,nested if..... concept in one(same) program...........
View Tutorial By: krishna at 2015-08-14 08:54:05
11. Write a times table programme. The programme should ask a user to input a number. This number is the
View Tutorial By: Hannah Jambalos at 2014-09-03 12:07:34
12. required the flag set loop stutruce ..............
View Tutorial By: savita at 2013-05-12 04:52:30
13. Hello! cedgbfa interesting cedgbfa site! I'm really like it! Very, very cedgbfa good!
View Tutorial By: Pharmc584 at 2013-02-24 03:56:18
14. There is possible to include 2 conditions in for loop using commas like
Ex:for(int i=0,j=5;i&
View Tutorial By: aarthi at 2012-12-10 12:08:50
15. int m,m2,n,n2;
for( m=0 , m2=0 ; m<r1 , m2<c2 ; m++ , m2++ ){
for(
View Tutorial By: muhammad abdullah at 2012-10-11 05:27:02
16. for(i=0;i<10;i++)
for(j=0;j<90;j++)
we two for loop.explan me in detail what the
View Tutorial By: karthikeyan at 2012-05-23 05:33:10
17. class loop8
{
public static void main(String args[])
{
View Tutorial By: ankush singh at 2011-11-04 16:26:36
18. // Using the comma.
class Comma {
public static void main(String args[]) {
i
View Tutorial By: Aruna at 2011-10-24 15:01:16
19. // Using the comma.
class Comma {
public static void main(String args[]) {
i
View Tutorial By: Aruna at 2011-10-24 14:58:42
20. I tried it/comma program works as illustrated,
in the line: for(a=1, b=4; a<b; a++, b&aci
View Tutorial By: Kelly at 2011-10-20 14:10:51
21. // Using the comma.
class Comma {
public static void main(String args[]) {
int
View Tutorial By: jatin kapoor at 2011-01-22 03:43:10
22. syntax of java program in looping statement
View Tutorial By: lokesh at 2009-03-25 06:57:56
23. Java is very queit Langauge.
View Tutorial By: Ashutosh Srivasatava at 2008-10-16 06:24:02
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