Java Output

A program that does not show anything is not very useful. In Java you print to the terminal with System.out, which has three methods you will use all the time: println, print and printf.

println and print

println prints its text and then moves to a new line. print prints its text and stays on the same line, so the next output continues right after it:

public class Main {
    public static void main(String[] args) {
        System.out.println("First line");
        System.out.print("Same ");
        System.out.print("line ");
        System.out.println("here.");
        System.out.println("Last line");
    }
}

First line
Same line here.
Last line

An empty System.out.println(); prints just a new line, which is a simple way to leave an empty line in the output.

Printing numbers and calculations

Numbers are written without quotes. If you print a calculation, Java works it out first and prints the result:

public class Main {
    public static void main(String[] args) {
        System.out.println(42);
        System.out.println(7 + 3);
        System.out.println(10 * 4);
        System.out.println("7 + 3");
    }
}

42
10
40
7 + 3

Look at the last line: with quotes, "7 + 3" is just text, so Java prints it as it is.

Special characters

Inside quotes, a backslash starts an escape sequence, a way to write characters you cannot type directly:

public class Main {
    public static void main(String[] args) {
        System.out.println("Name\tAge");
        System.out.println("Asha\t21");
        System.out.println("She said \"hello\".\nNew line here.");
    }
}

Name	Age
Asha	21
She said "hello".
New line here.

printf: formatted output

printf prints text with placeholders that are filled with values: %d for a whole number, %s for text, %.2f for a decimal number with two digits after the point, and %n for a new line.

public class Main {
    public static void main(String[] args) {
        System.out.printf("%s is %d years old.%n", "Ravi", 30);
        System.out.printf("Price: %.2f%n", 19.5);
    }
}

Ravi is 30 years old.
Price: 19.50

The String Formatting topic shows many more placeholders. For now, println is all you need, and printf is handy when numbers must look neat.

Practice exercises

1. Print your name, then on the same line your age, using one print and one println.
2. Print a small table with three rows of a name and a score, separated by \t.
3. Use printf to print the result of 22.0 / 7 with three digits after the point.