Control Statements in Java

Control statements in Java are used to control the flow of execution of the program based on certain conditions.

• Based on specific conditions, you can decide which block of code should be executed, repeated, or skipped.

Types of Control Statements:

• Conditional Statements
• Looping Statements
• Jump Statements

1.) Conditional Statements:

Conditional statements, also known as Selection statements, are control statements that allows a program to make decisions and execute certain blocks of code only when specific conditions are met.

• Conditional statements evaluate expressions (conditions) that return either true or false and perform actions based on these evaluations.

Types of Conditional Statements in Java:

• The if Statement
• The if-else statement
• The if-else if-else statement
• The switch Statement

a.) The if Statement:

• The if statement is used to execute a block of code if a condition is true. If the condition is false, it is skipped.

Syntax:

if (condition) {
    // Code to execute if condition is true
}

Example:

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

b.) The if-else statement:

• The if-else statement allows you to execute one block of code if the condition is true and another block if the condition is false.

Syntax:

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

Example:

int number = 5;
if (number % 2 == 0) {
    System.out.println("Even number");
} else {
    System.out.println("Odd number");
}

c.) The if-else if-else Statement:

The if-else if-else statement is used when you have multiple conditions to check. It allows you to test multiple conditions and execute code based on the first true condition.

Syntax:

if (condition1) {
    // Code
} else if (condition2) {
    // Code
} else {
    // Default code
}

Example:

int score = 75;
if (score >= 90) {
    System.out.println("Grade A");
} else if (score >= 75) {
    System.out.println("Grade B");
} else {
    System.out.println("Grade C");
}

d.) The switch Statement

The switch statement is used for scenarios where multiple conditions need to be checked.

Syntax:

switch (expression) {
    case value1:
        // Code
        break;
    case value2:
        // Code
        break;
    default:
        // Default code
}

Example:

int day = 3;
switch (day) {
    case 1: System.out.println("Sunday"); break;
    case 2: System.out.println("Monday"); break;
    case 3: System.out.println("Tuesday"); break;
    default: System.out.println("Invalid day");
}

2.) Looping statements:

Looping statements are used to execute a block of code repeatedly, either for a specific number of times or until a condition is met.

• A loop continues to execute as long as its condition remains true.
• Loops help in situations where repetitive tasks are required.

Types of Looping Statement in Java:

• for loop
• while loop
• do-while
• for-each

a.) for loop

The for loop is used when you know beforehand how many times you want to execute a statement or a block of statements.

Syntax:

for (initialization; condition; update) {
    // code block to be executed
}

Example:

for (int i = 1; i <= 5; i++) {
    System.out.println("Count: " + i);
}

b.) while loop

The while loop is used to execute a block of code as long as the specified condition is true. It checks the condition before executing the loop.

Syntax:

while (condition) {
    // code block to be executed
}

Example:

int i = 1;
while (i <= 5) {
    System.out.println("Count: " + i);
    i++;
}

c.) do-while Loop:

The do-while loop is used to executes the code block at least once before checking the condition.

Syntax:

do {
    // code block to be executed
} while (condition);

Example:

int i = 1;
do {
    System.out.println("Count: " + i);
    i++;
} while (i <= 5);

d.) for-each loop:

It is best for looping through arrays or collections when index is not needed.

Syntax:

for (dataType item : arrayName) {
    // code block to be executed
}

Example:

int[] numbers = {10, 20, 30};
for (int num : numbers) {
    System.out.println(num);
}

3.) Jumping Statements:

Jumping statements are used to alter the normal flow of program execution in loops or conditional blocks.

• They help manage the execution flow by skipping iterations, exiting loops, or stopping the program.

Java provides three primary jumping statements:

• break Statement
• continue Statement
• return Statement

a.) break Statement

The break statement is used to exit from a loop or a switch statement prematurely. It stops the execution of the loop or switch and transfers control to the next statement outside of the loop.

Example:

for (int i = 1; i <= 5; i++) {
    if (i == 3) {
        break; // exits loop when i is 3
    }
    System.out.println("i = " + i);
}

b.) continue Statement

The continue statement is used to skip the current iteration of a loop and move on to the next iteration. It does not terminate the loop; it just skips the code below it for the current iteration.

Example:

for (int i = 1; i <= 5; i++) {
    if (i == 3) {
        continue; // skips printing when i is 3
    }
    System.out.println("i = " + i);
}

c.) return Statement

The return statement exits from the current method and optionally returns a value.

Example:

public class ReturnExample {
    public static void main(String[] args) {
        System.out.println("Start");
        test();
        System.out.println("End");
    }

    static void test() {
        System.out.println("Inside test");
        return;
        // code here won't run
    }
}