Java Output

Introduction to Java Output

In Java, the term “output” refers to the data or results displayed to the user after executing a program. Output is a critical part of programming because it helps communicate the program’s results, debug issues or present user-readable information. Java provides several built-in methods for generating output, with the most commonly used being System.out.print() and System.out.println().

Java’s output mechanism is simple and powerful, enabling developers to display text, variables and results of calculations on the console.

How Does Java Handle Output?

Java uses the System.out object to handle standard output. This object has methods that send data to the console. These methods include:

• print(): Prints text or variables on the same line.
• println(): Prints text or variables on a new line.
• printf(): Formats output using a specified format.

Basic Syntax for Output in Java

Using System.out.print()
Syntax:

System.out.print("Text to display");

Example:

public class OutputExample {
    public static void main(String[] args) {
        System.out.print("Welcome to Java Programming!");
    }
}

Output:

Welcome to Java Programming!

Using System.out.println()
Syntax:

System.out.println("Text to display");

Example:

public class OutputExample {
    public static void main(String[] args) {
        System.out.println("Hello, World!");
        System.out.println("Learning Java is fun.");
    }
}

Output:

Hello, World!  
Learning Java is fun.

Using System.out.printf()
Syntax:

System.out.printf("Formatted text: %d", value);

Example:

public class OutputExample {
    public static void main(String[] args) {
        int age = 25;
        System.out.printf("I am %d years old.", age);
    }
}

Output:

I am 25 years old.

Examples of Output with Variables

Printing Variables
You can display the values of variables using System.out.print() or System.out.println().

Example:

public class VariableOutput {
    public static void main(String[] args) {
        String name = "Alice";
        int age = 20;
        double marks = 95.5;

        System.out.println("Name: " + name);
        System.out.println("Age: " + age);
        System.out.println("Marks: " + marks);
    }
}

Output:

Name: Alice  
Age: 20  
Marks: 95.5

Concatenation in Output
You can concatenate (combine) text and variables using the + operator.

Example:

public class ConcatenationExample {
    public static void main(String[] args) {
        int num1 = 10;
        int num2 = 20;

        System.out.println("Sum of numbers: " + (num1 + num2));
    }
}

Output:

Sum of numbers: 30

Output Formatting with printf()

The printf() method is useful when you need to format the output. It allows you to use format specifiers like %d, %s and %f.

Example:

public class FormattedOutput {
    public static void main(String[] args) {
        String product = "Laptop";
        int quantity = 5;
        double price = 599.99;

        System.out.printf("Product: %s%n", product);
        System.out.printf("Quantity: %d%n", quantity);
        System.out.printf("Price: $%.2f%n", price);
    }
}

Output:

Product: Laptop  
Quantity: 5  
Price: $599.99

Difference Between print() and println()

Feature	System.out.print()	System.out.println()
Line Break	Does not move to a new line.	Moves to a new line.
Use Case	Use for continuous output.	Use for output with line breaks.

Example:

public class PrintVsPrintln {
    public static void main(String[] args) {
        System.out.print("This is ");
        System.out.print("on the same line. ");
        System.out.println("This is on a new line.");
    }
}

Output:

This is on the same line. This is on a new line.

Common Mistakes in Java Output

Forgetting Semicolons:

• Every output statement must end with a semicolon (;).
• Example:

System.out.println("Hello") // Missing semicolon (Error)

Using Incorrect Quotes:

• Always use double quotes ( ” ) for strings. Single quotes ( ‘ ) are for characters.
• Example:

System.out.println('Hello'); // Error  

Mismatched Parentheses:

• Ensure parentheses match correctly.
• Example:

System.out.println("Hello"; // Error

Advanced Examples of Output in Java

Using Loops for Output
Example:

public class LoopOutput {
    public static void main(String[] args) {
        for (int i = 1; i <= 5; i++) {
            System.out.println("Number: " + i);
        }
    }
}

Output:

Number: 1  
Number: 2  
Number: 3  
Number: 4  
Number: 5

Printing Arrays
Example:

public class ArrayOutput {
    public static void main(String[] args) {
        String[] colors = {"Red", "Green", "Blue"};

        for (String color : colors) {
            System.out.println(color);
        }
    }
}

Output:

Red  
Green  
Blue