Basic Output

Java Output

You can simply use System.out.println(), System.out.print() or System.out.printf() to send output to standard output (screen).

System is a class and out is a public static field which accepts output data. Don't worry if you don't understand it. Classes, public, and static will be discussed in later chapters.

Let's take an example to output a line.

class AssignmentOperator {
    public static void main(String[] args) {
    	
    	System.out.println("Java programming is interesting.");   
    }
}

When you run the program, the output will be:

Java programming is interesting.

Here, println is a method that displays the string inside quotes.

What's the difference between println(), print() and printf()?

• print() - prints string inside the quotes.
• println() - prints string inside the quotes similar like print() method. Then the cursor moves to the beginning of the next line.
• printf() - it provides string formatting (similar to printf in C/C++ programming).

Example: print() and println()

class Output {
    public static void main(String[] args) {
    	
    	System.out.println("1. println ");
    	System.out.println("2. println ");
    	
    	System.out.print("1. print ");
    	System.out.print("2. print");
    }
}

When you run the program, the output will be:

1. println 
2. println 
1. print 2. print

Visit this page to learn about Java printf().

To display integers, variables and so on, do not use quotation marks.

Example: Printing Variables and Literals

class Variables {
    public static void main(String[] args) {
    	
    	Double number = -10.6;
    	
    	System.out.println(5);
    	System.out.println(number);
    }
}

When you run the program, the output will be:

5
-10.6

You can use + operator to concatenate strings and print it.

Example: Print Concatenated Strings

class PrintVariables {
    public static void main(String[] args) {
    	
    	Double number = -10.6;
    	
    	System.out.println("I am " + "awesome.");
    	System.out.println("Number = " + number);
    }
}

When you run the program, the output will be:

I am awesome.
Number = -10.6

Consider: System.out.println("I am " + "awesome.");

Strings "I am " and "awesome." is concatenated first before it's printed on the screen.

Consider: System.out.println("Number = " + number);

The value of variable number is evaluated first. It's value is in double which is converted to string by the compiler. Then, the strings are concatenated and printed on the screen.