GFG Day 4: Conditional Statements

• A conditional statement is a program that makes decisions and executes different blocks of code based on the condition being true or false.

• This conditional statement, also known as decision-making in programming, is similar to decision-making in real life. Java provides several control statements to manage program flow, including:

  • Conditional Statements: if, if-else, nested-if, if-else-if

  • Switch case: For multiple fixed-values checks

  • Jump Statements: break, continue, return

Types of Decision-Making Statements

• if

• if-else

• nested-if

• if-else-if

• switch-case

• break, continue, return

The table below demonstrates various control flow statements in programming, their use cases, and examples of their syntax.

1. Java if Statement

• The if statement executes the code if the condition is true; it executes the code inside the curly brackets { }.

Syntax

if(condition) {

// Statements to execute if condition is true

}

If statement execution flowchart

The Java program below demonstrates that if the condition is true, the code inside the curly braces will execute.

// file name: ifcondition.java
public class ifcondition{
    public static void main (String[] args) {
        int age = 20;
        if(age >= 18){ // here age 20 is greater than 18 so true and execute
            System.out.println("Eligible to vote");
        }
    }
}

Output

Eligible to vote

Explanation

• The condition age evaluates Boolean value

• If the condition is true, the code inside the curly bracket is executed

• If the condition is false, code will be skipped.

2. Java if-else Statement

• An if-else statement is used to run a block of code when the condition in the if statement evaluates to false.

Syntax

if(condition){

// Executes this block if condition is true

} else {

// Executes this block if condition is false

}

if-else Statement Execution Flowchart

The below Java program demonstrates the use of the if-else statement to execute different blocks of code based on the condition.

// file name: ifelsecondition.java
public class ifelsecondition{
    public static void main (String[] args) {
        int age = 15;
        if(age >= 18){ // here age is less than 18 so if statement false and not execute
            System.out.println("Eligible to vote");
        } else { // here age is less than 18 so true else statement true and execute
            System.out.println("Not eligible to vote");
        }
    }
}

Output

Not eligible to vote

Explanation

• The condition age evaluates Boolean value

• If the if statement is false, the code inside the curly bracket is not executed

• If the else statement is true, the code inside the curly bracket is executed

3. Java nested-if statement

• A nested if statement means a if statement inside another if statement. To perform the second if statement, the condition of the first if statement must be true.

Syntax

if (condition1) {

// Executes when condition1 is true or false

if (condition2)

{

// Executes when condition2 is true

}

}

nested-if Statement Execution Flow

The below Java program demonstrates the use of nested if statements to check multiple conditions.

// file name: nestedif.java
public class nestedif{
    public static void main (String[] args) {
        int age = 25;
        boolean hasId = true;
        if(age >= 18){
            if(hasId){
                System.out.println("Access Granted");
            } else {
                System.out.println("Id required for verification");
            }
        } else {
            System.out.println("You must be 18+ to enter");
        }
    }
}

Output

Access Granted

4. Java if-else-if ladder

• The else-if statement is used to check multiple conditions in sequence when the previous if condition is false.

Syntax

if (condition1) {

// code to be executed if condition1 is true

} else if (condition2) {

// code to be executed if condition2 is true

} else {

// code to be executed if all conditions are false

}

if-else-if ladder Execution Flow

This example demonstrates an if-else-if ladder to check multiple conditions and execute the corresponding block of code based on the score grade.

// file name: ifelseif.java
public class ifelseif{
    public static void main (String[] args) {
        int score = 75;
        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 D");
        }
    }
}

Output

Grade c

5. Java Switch case

• In the switch case, depending on the variable value, that particular case will be executed. If the variable value doesn’t match any case, the default value will be executed.

• In every case, we have to use the break keyword. If we use the break keyword, the program will terminate (stop) without executing the next line.

Syntax

switch (expression) {

case value1:

// code to be executed if expression == value1

break;

case value2:

// code to be executed if expression == value2

break;

// more cases...

default:

// code to be executed if no cases match

}

switch Statements Execution Flow

The below Java program demonstrates the use of the switch-case statement to evaluate multiple fixed values.

// file name: switchcase.java
public class switchcase{
    public static void main (String[] args) {
        int num = 2;
        switch (num) {
        case 1:
            System.out.println("Monday");
            break;
        case 2:
            System.out.println("Tuesday");
            break;
        case 3:
            System.out.println("Wednesday");
            break;
        case 4:
            System.out.println("Thursday");
            break;
        case 5:
            System.out.println("Friday");
            break;
        default:
            System.out.println("Weekend");
        }
    }
}

Output

Tuesday

• The expression can be of type byte, short, int, char, or an enumeration. Beginning with JDK7, the expression can also be of type String.

• Duplicate case values are not allowed.

• The default statement is optional.

• The break statement is used inside the switch to terminate a statement sequence.

• The break statements are necessary; without the break keyword, statements in switch blocks fall through.

• If the break keyword is omitted, execution will continue to the next case.

6. Jump Statement

• Java supports three jump statements: break, continue and return. These three statements transfer control to another part of the program.

  • Break: In Java, a break is majorly used to terminate a sequence in a switch statement (discussed above) and to exit a loop.

  • Continue: continue keyword is used in a looping statement. it is used to skip the remaining code in the current iteration and continue the next iteration.

  • Return: The return statement is used to explicitly return from a method. That is, it causes program control to transfer back to the caller of the method.

The Java program below demonstrates how the continue statement skips the current iteration when a condition is true.

// file name: jumpstatement.java
public class jumpstatement{
    public static void main (String[] args) {

        for (int i = 0; i < 10; i++) {

            // If the number is even
            // skip and continue
            if (i % 2 == 0){
                continue;
            }
            // If number is odd, print it
            System.out.print(i + " ");

        }
    }
}

Output

1 3 5 7 9

The below Java program demonstrates how the return statements stop a method and skips the rest of the code.

// file name: jumpstatement.java
public class jumpstatement{
    public static void main (String[] args) {

        boolean t = true;
        System.out.println("Before the return.");

        if (t){
            return;
        }
        // Compiler will bypass every statement
        // after return
        System.out.println("This won't execute.");
    }
}

Output

Before the return.

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Happy Learning

Thanks For Reading! :)

SriParthu 💝💥