Conditionals and Loops

Condition: It provides check for the statement.

1. if-else statement:- It is used to check the condition, it checks the boolean condition True or false.

Syntax:-

if (boolean expression True or false) {
    //Body
} else {
    //Do this
}

Example:-

public class IfElse {
    public static void main(String[] args) {
        int salary = 20000;
        if (salary > 10000) {
            salary = salary + 2000;
        } else {
            salary = salary + 1000;
        }

        System.out.println(salary);
    }
}

//Output
22000

2. Multiple if-else statement:- It executes one condition from multiple statements.

Syntax:-

if (condition 1) {
    // code to be executed if condition 1 is true
} else if (condition 2) {
    // code to be executed if condition 2 is true;
} else if (condition 3) {
    // code to be executed if condition 3 is true;
} else {
    // code to be executed if all conditions are false;
}

Example:-

public class MultipleIfElse {
    public static void main(String[] args) {
        int salary = 20000;
        if (salary <= 10000) {
            salary = salary + 1000;
        } else if (salary <= 20000) {
            salary = salary + 2000;
        } else {
            salary = salary + 3000;
        } 

        System.out.println(salary);
    }
}

//Output
25000

Loop:- Loops are used to iterate a part of program several times.

1. for loop:- It is generally used when we know how many times loop will iterate.

Syntax:-

for (initialization; condition; increment/decrement) {
    //body
}

Example:- Print numbers from 1 to 5.

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

//Output
1
2
3
4
5

2. While Loop:- It is used when we don't know how many time the loop will iterate.

Syntax:-

while (condition) {
    //code to be executed 
    // increment/decrement
}

Example:-

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

//Output
1
2
3
4
5

3. do while loop:- It is used when we want to execute our statement at least one time. It is called exit control loop because it checks the condition after execution of statement.

Syntax:-

do {
    // code to be executed
    // update statement -> increment/decrement
} while (condition);

Example:-

public class DoWhileLoop {
    public static void main(String[] args) {
        int n = 1;

        do {
            System.out.println(n);
            n++;
        } while (n <= 5);
    }
}

//Output
1
2
3
4
5

Switch statement:- A switch is a multiple-choice decision-making statement.

Syntax:-

switch (expression) {
    case one:
        // Code block
        break;//---> terminate the sequence
    case two:
        // Code block
        break;
    // Add more cases as needed
    default://---> default will execute when none of the above does
        // Code block
}

• If break is not used then it will continue with other cases.

public class SwitchWithoutBreak {
    public static void main(String[] args) {
        int choice = 2;

        switch (choice) {
            case 1:
                System.out.println("Case 1");
                // No break, falls through to the next case

            case 2:
                System.out.println("Case 2");
                // No break, falls through to the next case

            case 3:
                System.out.println("Case 3");
                // No break, falls through to the next case

            default:
                System.out.println("Default Case");
                // No break needed at the end
        }
    }
}

• Duplicate cases are not allowed.

code one:
    //code block
    break;
code one://----> Duplicate cases not allowed
    //code block
    break;

Nested Switch case: Nested-Switch statements refer to Switch statements inside of another Switch Statements.

switch (expression) {
    case one:
        // code block
        break;
    case two:
        switch (expression) {
            case one:
                // code block
                break;
            case two:
                // code block
                break;
            default:
                // code block
                break;
        }
        break;
    default:
        // code block
}

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