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Control Statements

If Statement

This is the simplest form of conditional statement and is fundamental to decision-making in Java programming.

if statement allows you to execute a code block only if a specified condition is true.

Syntax

if (condition) {
    // code to be executed if condition is true
}

condition: This is a boolean expression that evaluates to either true or false. If the condition evaluates to true, then the block of code enclosed in curly braces {} will be executed.

Simple if

This is the most used control statement in all programming languages. Let us see an example code snippet.

public class Main {
    public static void main(String[] args) {
        int number = 10;

        // if statement
        if (number > 5) {
            System.out.println("The number is greater than 5.");
        }

        System.out.println("This statement is always executed.");
    }
}

// Outputs:
// The number is greater than 5.
// This statement is always executed.

In this example:

  • The condition number > 5 is evaluated.
  • Since number is 10, which is greater than 5, the condition evaluates to true.
  • Therefore, the code inside the if block (System.out.println("The number is greater than 5.");) is executed.
  • The subsequent System.out.println("This statement is always executed."); line is outside the if block and is executed regardless of the condition.

Multiple Conditions

You can use multiple if statements to check multiple conditions independently:

public class Main {
    public static void main(String[] args) {
        int number = 10;

        if (number > 5) {
            System.out.println("The number is greater than 5.");
        }

        if (number < 20) {
            System.out.println("The number is less than 20.");
        }
    }
}
// Outputs:
// The number is greater than 5.
// The number is less than 20.

In this example:

  • The first if statement checks if number is greater than 5.
  • The second if statement checks if number is less than 20.
  • Both conditions are true, so both messages are printed.

Nested if Statements

if statements can be nested inside other if statements to handle more complex conditions:

public class Main {
    public static void main(String[] args) {
        int number = 10;

        if (number > 5) {
            if (number < 15) {
                System.out.println("The number is between 5 and 15.");
            }
        }
    }
}

// Outputs:
// The number is between 5 and 15.

In this example:

  • The outer if statement checks if number is greater than 5.
  • If true, the inner if statement then checks if number is less than 15.
  • Since both conditions are true, "The number is between 5 and 15." is printed.

Logical Operators

You can also use logical operators to combine multiple conditions in a single if statement:

public class Main {
    public static void main(String[] args) {
        int number = 10;

        if (number > 5 && number < 15) {
            System.out.println("The number is between 5 and 15.");
        }
    }
}

// Outputs:
// The number is between 5 and 15.

In this example:

  • The condition number > 5 && number < 15 uses the logical AND operator (&&) to check if both conditions are true.
  • Since number is 10, both conditions are true, and the message is printed.

Summary

  • The if condition allows you to execute code based on whether a condition is true.
  • It is a basic but powerful tool for decision-making in Java.
  • Conditions are boolean expressions that evaluate to true or false.
  • You can use multiple if statements, nested if statements, and logical operators to handle more complex decision-making.

Using the if statement effectively enables you to control the flow of your Java programs based on dynamic conditions.