Loops

Loops in Java:

1. While Loop:

• In while loop, the loop-continuation-condition acts like an if statement. The loop will execute the statements repeatedly when the loop-continuation-condition is true.
• In the loop body, we need to have an update statement that will eventually make the loop-continuation-condition false, so the loop will terminate.

Syntax:

while (loop-continuation-condition) 
{
    // Loop body
    statements;
    update-statement;
}

2. Do-while Loop:

• Unlike regular while loop, do-while loop it always executed at least once, since loop body is executed before the loop-continuation-condition is evaluated.
• while statement behaves the same way as the regular while loop.
• while and do-while loops can be easily converted but using one or the other can be beneficial in some scenarios.

Syntax:

do { 
    // Loop body;
    statements;
    update-statement;
} while (loop-continuation-condition);

3. For Loop:

Syntax:

for (initial-action; loop-continuation-condition; 
    action-after-each-iteration) {
    // Loop body;
    statements;
}

It can be converted to a while loop:

initial-action;
while (loop-continuation-condition) {
    // Loop body;
    statements;
    action-after-each-iteration;
}

More precisely, these two loops are interchangable:

for (i = initialValue; i < endValue; i++) {
 // Loop body
 ...
}

i = initialValue; // Initialize loop control variable 
while (i < endValue) {
 // Loop body
 ...
 i++; // Adjust loop control variable
}

4. For-each Loop:

• We generally use this type of loop to iterate over the elements of a list of items. (Could be an ArrayList as an example)
• If we want to keep track of the index, or we want to skip some elements, it is better to use normal for loop.

Syntax:

for (type var : array) 
{ 
    // Loop body
    statements using var;
}

It is same as this for loop:

for (int i=0; i<arr.length; i++) 
{ 
    // Loop body
    type var = arr[i];
    statements using var;
}

5. Nested Loops: