Control  Statements

Control statement is used to control the flow of execution depending on some specific condition.

Types of Control Statement

1. Conditional Control Statement

2. Un-Conditional Control Statement

3. Looping Control Statement

1. Conditional Control Statement : 

It is used to make decisions in code based on certain conditions.

Types of Conditional Control Statements

1. if statement :

2. if-else statement :

3. if-else-if ladder :

4. switch statement :

1. if Statement

Used when you want to execute code only if a condition is true

java

if (condition) {
    // code executes if condition is true
}

java

int age = 20;

if (age >= 18) {
    System.out.println("You are eligible to vote");
}

// output : You are eligible to vote

• Condition must return boolean (true/false)

• Executes only when condition = true

• No action if condition is false

2. if-else Statement

Used when you want one block if true, another if false

java

if (condition) {
    // true block
} else {
    // false block
}

java

int number = 10;

if (number % 2 == 0) {
    System.out.println("Even number");
} else {
    System.out.println("Odd number");
}

// output :  Even number

• Only one block executes

• else is optional but useful

• Improves decision making

3. if-else-if Ladder

Used when you have multiple conditions

java

if (condition1) {
    // block 1
} else if (condition2) {
    // block 2
} else if (condition3) {
    // block 3
} else {
    // default block
}

java

int marks = 75;

if (marks >= 90) {
    System.out.println("Grade A");
} else if (marks >= 70) {
    System.out.println("Grade B");
} else if (marks >= 50) {
    System.out.println("Grade C");
} else {
    System.out.println("Fail");
}

// output :  Grade B

• Conditions checked top to bottom

• First true condition executes

• Remaining conditions are skipped

• else is optional (default case)

4. SWITCH Statement

Used when comparing one variable with multiple fixed values

javascript

switch (variable) {
    case value1:
        // code
        break;

    case value2:
        // code
        break;

    default:
        // default code
}

javascript

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");
}

// output  : Wednesday

Java 17 Modern Switch

Since you're using Java 17

plaintext

int day = 2;

switch (day) {
    case 1 -> System.out.println("Monday");
    case 2 -> System.out.println("Tuesday");
    case 3 -> System.out.println("Wednesday");
    default -> System.out.println("Invalid");
}

• No need for break

• Cleaner & modern

• Used in real projects

2. Un-Conditional Control Statement

Unconditional Control Statements are used to change the normal flow of execution in a program without checking any condition. These are not dependent on any boolean expressions — they just perform an action directly.

Types of Unconditional Control Statements:

1. break

2. continue

3. return

3. Looping Control Statement

Looping control statements are used to repeat a block of code multiple times until a certain condition is met.

Types of Loops in Java

for loop

• When you already know the number of iterations

• Example: printing numbers from 1 to 10

java

for(initialization; condition; update) {
    // code
}

Example:

java

public class Main {
    public static void main(String[] args) {
        
        for(int i = 1; i <= 5; i++) {
            System.out.println(i);
        }
        
    }
}

🔍 Explanation:

• int i = 1 → starting point

• i <= 5 → condition check

• i++ → increment (increase value)

while loop

• When the loop is condition-based

• When you don’t know the exact number of iterations

java

while(condition) {
    // code
}

java

public class Main {
    public static void main(String[] args) {
        
        int i = 1;
        
        while(i <= 5) {
            System.out.println(i);
            i++;
        }
        
    }
}

🔍 Explanation:

• First, the condition is checked

• If the condition is false, the loop will not run at all

do-while loop

• When you want the loop to run at least once, no matter what

java

do {
    // code
} while(condition);

java

public class Main {
    public static void main(String[] args) {
        
        int i = 1;
        
        do {
            System.out.println(i);
            i++;
        } while(i <= 5);
        
    }
}

 Basic Loop Questions

1. Print numbers from 1 to 10 using a for loop.

2. Print even numbers between 1 to 50.

3. Print odd numbers between 1 to 50.

4. Print the sum of numbers from 1 to N.

5. Find the sum of even and odd numbers separately from 1 to N.

 Pattern  Questions

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