While loop execution flow in Java - Step-by-Step Execution

Concept Flow - While loop execution flow

Initialize variable

↓

Check condition

Yes↓

Execute loop body

↓

Update variable

Back to Check↓

Exit loop

↩Back to Check

The while loop starts by checking a condition. If true, it runs the loop body, updates variables, then checks again. It stops when the condition is false.

Execution Sample

Java

int i = 0;
while (i < 3) {
    System.out.println(i);
    i++;
}

Prints numbers 0, 1, 2 by looping while i is less than 3.

Execution Table

Step	i value	Condition (i < 3)	Action	Output
1	0	true	Print 0; i = i + 1	0
2	1	true	Print 1; i = i + 1	1
3	2	true	Print 2; i = i + 1	2
4	3	false	Exit loop

💡 i reaches 3, condition 3 < 3 is false, loop stops

Variable Tracker

Variable	Start	After 1	After 2	After 3	Final
i	0	1	2	3	3

Key Moments - 3 Insights

Why does the loop stop when i equals 3?

Because the condition i < 3 becomes false at step 4, so the loop exits as shown in the execution_table row 4.

When is the variable i updated in the loop?

i is updated after printing in each loop iteration, as shown in the Action column of execution_table rows 1 to 3.

Does the loop body run if the condition is false at the start?

No, the condition is checked before the loop body runs. If false initially, the loop body never executes.

Visual Quiz - 3 Questions

Look at the execution table, what is the value of i at step 2?

A 1

B 0

C 2

D 3

💡 Hint

Check the 'i value' column in execution_table row 2.

At which step does the condition become false and the loop stops?

A Step 3

B Step 2

C Step 4

D Step 1

💡 Hint

Look at the 'Condition' column in execution_table to find when it is false.

If we change the initial i to 3, what happens to the loop execution?

A Loop runs once

B Loop does not run at all

C Loop runs three times

D Loop runs infinitely

💡 Hint

Recall that the condition is checked before the loop body runs, see key_moments about initial condition.

Concept Snapshot

while (condition) {
    // code runs while condition is true
    // update variables inside to avoid infinite loop
}

- Condition checked before each loop
- Loop stops when condition is false
- Variables usually updated inside loop

Full Transcript

This visual shows how a while loop works in Java. First, a variable i is set to 0. Then the loop checks if i is less than 3. If yes, it prints i and adds 1 to i. This repeats until i reaches 3, when the condition becomes false and the loop stops. The execution table tracks each step, showing i's value, the condition result, the action taken, and the output printed. The variable tracker shows how i changes after each loop. Key moments explain why the loop stops and when i updates. The quiz tests understanding of i's value at steps, when the loop ends, and what happens if i starts at 3.