Control Flow

Control flow statements determine the order in which instructions are executed. Java provides conditionals (if, switch) and loops (for, while, do-while) to make programs dynamic and responsive.

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If / Else

int score = 85;

if (score >= 90) {
    System.out.println("Grade: A");
} else if (score >= 80) {
    System.out.println("Grade: B");
} else if (score >= 70) {
    System.out.println("Grade: C");
} else {
    System.out.println("Grade: F");
}

Comparison Operators

Operator	Meaning
==	Equal to
!=	Not equal to
>	Greater than
<	Less than
>=	Greater than or equal to
<=	Less than or equal to

Logical Operators

Operator	Meaning	Example
&&	AND	a > 0 && b > 0
||	OR	a > 0 || b > 0
!	NOT	!finished

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Ternary Operator

A concise alternative to simple if/else:

String result = (score >= 60) ? "Pass" : "Fail";

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Switch Statement

Classic Switch

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("Other day");
}

Enhanced Switch (Java 14+)

No break needed — uses arrow syntax:

String dayName = switch (day) {
    case 1 -> "Monday";
    case 2 -> "Tuesday";
    case 3 -> "Wednesday";
    case 4 -> "Thursday";
    case 5 -> "Friday";
    case 6 -> "Saturday";
    case 7 -> "Sunday";
    default -> "Invalid";
};

Tip: The enhanced switch is both an expression (returns a value) and eliminates fall-through bugs caused by missing break statements.

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For Loop

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

Enhanced For-Each Loop

Used to iterate over arrays and collections:

String[] fruits = {"Apple", "Banana", "Cherry"};

for (String fruit : fruits) {
    System.out.println(fruit);
}

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While Loop

Repeats while a condition is true:

int count = 0;

while (count < 3) {
    System.out.println("Count: " + count);
    count++;
}

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Do-While Loop

Executes the body at least once, then checks the condition:

int num = 0;