Java Basics Tutorial: Mastering Control Flow Statements

Welcome to your comprehensive guide to Java control flow statements! We'll break down each concept with clear examples and detailed explanations to ensure you grasp these fundamental programming constructs.

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1. If-then/if-then-else Statement

int age = 18;
if (age >= 18) {
    System.out.println("You are an adult!");
} else {
    System.out.println("You are a minor!");
}

How it works:

We declare an integer variable age and initialize it with value 18
The if condition checks if age is 18 or older
If true (which it is in this case), executes the first code block
If false, would execute the else block
Curly braces {} define the code blocks for each condition

Output: "You are an adult!"

2. Switch-case Statement

int day = 3;
switch(day) {
    case 1: System.out.println("Monday"); break;
    case 2: System.out.println("Tuesday"); break;
    case 3: System.out.println("Wednesday"); break;
    default: System.out.println("Invalid day");
}

Key points:

Evaluates the day variable against multiple cases
break prevents "falling through" to next cases
default case handles unexpected values
Works with: byte, short, char, int, enums, and Strings

Output: "Wednesday"

3. For Loop

for(int i = 0; i < 5; i++) {
    System.out.println("Count: " + i);
}

Structure breakdown:

Initialization: int i = 0 (runs once at start)
Condition: i < 5 (checked before each iteration)
Increment: i++ (executes after each iteration)

Execution Flow:
0 → 1 → 2 → 3 → 4 (stops when i reaches 5)

4. Do-while Loop

int count = 5;
do {
    System.out.println("Count: " + count);
    count--;
} while(count > 0);

Special feature:

Guarantees at least one execution
Condition check happens after loop body
Useful for menu systems or input validation

Output sequence: 5, 4, 3, 2, 1

5. Break, Continue & Return

// Break example
for(int i = 0; i < 10; i++) {
    if(i == 5) break;
    System.out.println(i);
}

// Continue example
for(int i = 0; i < 5; i++) {
    if(i == 2) continue;
    System.out.println(i);
}

// Return example
public int add(int a, int b) {
    return a + b;
}

Break: Exits the loop immediately

Continue: Skips current iteration, continues next

Return: Exits method and optionally returns value

Outputs:
Break: 0-4
Continue: 0,1,3,4
Return: Returns sum of two numbers

6. Static & Final Keywords

// Static example
class Counter {
    static int count = 0;
    Counter() { count++; }
}

// Final example
final double PI = 3.14159;

Static:

Belongs to class rather than instances
All objects share the same static variable
Creating 3 Counter objects makes count = 3

Final:

Makes variable constant/unchangeable
Attempting to modify PI causes error
Naming convention: ALL_CAPS

7. Nested Loops

for(int i = 1; i <= 3; i++) {
    for(int j = 1; j <= 3; j++) {
        System.out.print(i*j + " ");
    }
    System.out.println();
}

Pattern explanation:

Outer loop runs 3 times (i=1,2,3)
Inner loop completes full cycle for each outer iteration
Prints multiplication table rows

Output:
1 2 3
2 4 6
3 6 9

Conclusion

You've now explored Java's core control flow mechanisms. Remember:

Conditionals (if/switch) make decisions
Loops (for/while) handle repetition
Keywords modify flow behavior

Practice creating different combinations and observe the results. Try modifying these examples - change values, remove breaks, or nest different loop types!

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Java Basics Tutorial: Mastering Control Flow Statements