LOOPING STATEMENTS, JAVA,PROGRAMMING LOGIC

Outline
Looping Statement
While loop
Do-while loop
For loop
For each loop
Nested Loops
Break Statement
Continue Statement

Looping Statement
 Looping in programming languages is a
feature which facilitates the execution of a set
of instructions/functions repeatedly while
some condition evaluates to true.
 Java provides three ways for executing the
loops. While all the ways provide similar basic
functionality, they differ in their syntax and
condition checking time.
 While loop
 Do-while loop
 For

While Loop
Loops through a block of code as long as a specified condition is true:
Syntax:
while (condition)
{
//code to be executed
Increment / decrement statement
}
Note:
Do not forget to increase the variable used in the condition,
otherwise the loop will never end!

While Loop
 while loop is used to iterate a part of the program several times.
 while is an example of entry controlled loop.
 If the number of iteration is not fixed, it is recommended to use while loop.
// Program to display numbers from 1 to 5
class Main
{
public static void main(String[] args)
{
int i = 1, n = 5;
while(i <= n)
{
System.out.println(i);
i++;
}
}
}
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Do-while Loop
 The do/while loop is a variant of the while loop.
 This loop will execute the code block once, before checking if the condition is
true, then it will repeat the loop as long as the condition is true.
 Syntax:
do{
//code to be executed / loop body
//update statement
}while(condition);

Do-while Loop
 do-while loop is executed at least once because condition is checked after loop
body.
 the do-while loop is an example of an exit-controlled loop.
// Java Program to display numbers from 1 to 5
import java.util.Scanner;
class Main
{
{
int i = 1, n = 5;
do
{
i++;
} while(i <= n);
}
}
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For Loop
 for loop is used for executing a part of the
program repeatedly.
 When the number of iteration is fixed then
it is suggested to use for loop
Syntax:
for(initialization; condition; increment/
decrement)
{
//statement or code to be executed
}

For Loop
1. Initialization:
 It is the initial condition which is executed once when the loop starts.
 Here, we can initialize the variable, or we can use an already initialized variable.
2.Condition:
 It is the second condition which is executed each time to test the condition of the loop.
 It continues execution until the condition is false.
 It must return boolean value either true or false.
3. Increment/Decrement(Updation):
 It increments or decrements the variable value.
4. Statement:
 The statement of the loop is executed each time until the second condition is false.

For Loop
// Program to print numbers from 1 to 5
class Main
{
public static void main(String[]
args)
{
int n = 5;
for (int i = 1; i <= n; ++i)
{
}
}
}
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For Each Loop in Java
 For-each is another array traversing technique like for loop, while loop, do-while
loop introduced in Java5.
 It starts with the keyword for like a normal for-loop.
 Instead of declaring and initializing a loop counter variable, you declare a
variable that is the same type as the base type of the array, followed by a colon,
which is then followed by the array name.
 In the loop body, This variable is used to access the array/collection elements
without any indexing.
 It’s commonly used to iterate over an array or a Collections class (eg, ArrayList)

Syntax:
for (type var : array)
{
statements using var;
}

 Example

Nested Loops in Java
 Every loop consists of below 3 things inside
them:
 Initialization: This step refers to initializing the
value of the counter.
 Condition: This condition refers to the
comparison that needs to be true for continuing
the execution of the loop.
 Increment/Decrement of counter: This refers to
the operation to be performed on the counter
once one flow of loop ends.
 In the case of nested loops, the above three
steps are checked for each loop inside it.
 Thus with each flow of the outer loop, the inner
loop executes completely, which means if we
have m flows for the outer loop and n number
of flows for the outer loop, then this loop

Half Pyramid Pattern using Nested Loops
// Java Program to print a Half pyramid pattern
class Demo
{
{
for(int i=0;i<5;i++)
{
for(int j=0;j<5;j++)
{
if(i>=j)
{
System.out.print('*’);
}
}
System.out.println("n");
}
}
}

Half Pyramid Pattern using Nested Loops

Programs to perform (Looping Statements)
 Write a program to print first n odd numbers.
 Write a program to check that the given number is prime or not.
 Write a program to draw given patterns.

Java Break Statement
 Break statement is used to break loop or switch statement.
 It breaks the current flow of the program at specified condition.
 We can use Java break statement in all types of loops such as
 for loop
 while loop
 do-while loop

Break Statement Example
class Test
{
{
for (int i = 1; i <= 10; ++i)
{
if (i == 5)
{
break;
}
}
}
}
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 When a break statement is encountered inside a
loop, the loop is immediately terminated and the
program control resumes at the next statement
following the loop.

Break Statement with Inner Loop
//outer loop
for(int i=1;i<=3;i++)
{
//inner loop
for(int j=1;j<=3;j++)
{
if(i==2&&j==2)
{
break;
}
System.out.println(i+" "+j);
}
}
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Labeled Break Statement
aa:
{
bb:
{
if(i==2&&j==2)
{
break aa;
}
}
}
Outp
ut:
1 1
1 2
1 3
2 1

Java Continue Statement
 Continue statement
breaks one iteration (in
the loop), if a specified
condition occurs, and
continues with the next
iteration in the loop.

Continue Statement Example
class Main
{
{
for (int i = 1; i <= 10; ++i)
{
// if value of i is between 4 and 9 continue is executed
if (i > 4 && i < 9)
{
continue;
}
}
}
}
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 The continue statement is used in loop control
structure when you need to immediately jump to the
next iteration of the loop.

Continue Statement with Inner Loop
//outer loop
{
//inner loop
{
if(i==2&&j==2)
{
continue;
}
}
}
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Continue Statement with Labeled For Loop
aa:
{
bb:
{
if(i==2&&j==2)
{
continue aa;
}
}
}
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LOOPING STATEMENTS, JAVA,PROGRAMMING LOGIC

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