Java Operators, Control Flow, and Comments

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Java Operators, Control Flow, and Comments
1. Java Operators
Operators in Java perform operations on variables and values.

1.1 Arithmetic Operators
Used for mathematical calculations.

Operator Description Example
+ Addition a + b
- Subtraction a - b
* Multiplication a * b
/ Division a / b
% Modulus (Remainder) a % b
✅ Example:

public class ArithmeticExample {

    public static void main(String[] args) {

        int a = 10, b = 5;

        System.out.println("Sum: " + (a + b)); // 15

        System.out.println("Difference: " + (a - b)); // 5

        System.out.println("Product: " + (a * b)); // 50

        System.out.println("Quotient: " + (a / b)); // 2

        System.out.println("Remainder: " + (a % b)); // 0

    }

}

1.2 Relational (Comparison) Operators
Used to compare values, returning true or false.

Operator Description Example
== Equal to a == b
!= Not equal to a != b
> Greater than a > b
< Less than a < b
>= Greater than or equal to a >= b
<= Less than or equal to a <= b
✅ Example:

public class RelationalExample {

    public static void main(String[] args) {

        int x = 10, y = 5;

        System.out.println(x > y);  // true

        System.out.println(x < y);  // false

        System.out.println(x == y); // false

        System.out.println(x != y); // true

    }

}

1.3 Logical Operators
Used in boolean expressions to combine conditions.

Operator Description Example
&& Logical AND a > b && a > c
` `
! Logical NOT !(a > b)
✅ Example:

public class LogicalExample {

    public static void main(String[] args) {

        boolean a = true, b = false;

        System.out.println(a && b); // false

        System.out.println(a || b); // true

        System.out.println(!a);     // false

    }

}

2. Control Flow Statements
Control flow statements help in decision-making and loops.

2.1 If-Else Statement
Executes a block of code based on a condition.

✅ Example:

public class IfElseExample {

    public static void main(String[] args) {

        int num = 10;



        if (num > 0) {

            System.out.println("Positive number");

        } else {

            System.out.println("Negative number");

        }

    }

}

2.2 Switch Statement
Used when multiple conditions are checked against a single variable.

✅ Example:

public class SwitchExample {

    public static void main(String[] args) {

        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

2.3 Loops
Loops execute a block of code multiple times.

1. For Loop
✅ Example:

public class ForLoopExample {

    public static void main(String[] args) {

        for (int i = 1; i <= 5; i++) {

            System.out.println("Count: " + i);

        }

    }

}

💡 Output:

Count: 1  

Count: 2  

Count: 3  

Count: 4  

Count: 5  

2. While Loop
Executes as long as a condition is true.

✅ Example:

public class WhileLoopExample {

    public static void main(String[] args) {

        int i = 1;

        while (i <= 5) {

            System.out.println("Number: " + i);

            i++;

        }

    }

}

3. Do-While Loop
Executes at least once, then checks the condition.

✅ Example:

public class DoWhileExample {

    public static void main(String[] args) {

        int i = 1;

        do {

            System.out.println("Number: " + i);

            i++;

        } while (i <= 5);

    }

}

3. Comments in Java
Comments help make the code more readable and are ignored by the compiler.

3.1 Single-Line Comment

// This is a single-line comment

int x = 5;

3.2 Multi-Line Comment


/*
This is a
multi-line comment
*/

int y = 10;

3.3 Documentation Comment (for JavaDocs)

/**
* This method prints a greeting message.
*/
public void greet() {
System.out.println("Hello!");
}