Java Basic Input and Output

 Java output

In Java you can just use

System.out.println(); or

System.out.print(); or

System.out.printf();

to send the output to the standard output (screen).

Here,

  • The System is a class
  • out is a public static field: it accepts output data.

Don't worry if you don't understand it. We will discuss the class, public and static in the following chapters.

Let's take an example to pull out a line.

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

Output:

Java programming is interesting.

Here we have used the println() method to display the string.

Difference between println (), print () and printf ()

print() - It prints a string inside the quotes.

println() - It prints a string inside quotes similar to the print() method. Then the cursor moves to the start of the next line.

printf() - Tt 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");
    }
}

Output:

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

In the example above, we showed how the print () and printf () methods work.

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

Here you can see that we haven't used the quotes. This is because to display integers, variables, etc., we don't use quotes.

Example: Printing 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);
    }
}
Output:

I am awesome.
Number = -10.6
In the example above, note the line,

System.out.println("I am " + "awesome.");
Here we have used the + operator to concatenate (join) the two strings: "I am "and "awesome.".
And also, the line,

System.out.println("Number = " + number);
Here, the value of the variable number is first evaluated. Then the value is concatenated to the string: "Number = ".

Java input

Java provides several ways to get user information. However, in this tutorial, you will learn how to get user information using the object of the Scanner class.
To use the Scanner object, we need to import the java.util.Scanner package.

import java.util.Scanner; 

To learn more about importing packages into Java, visit Java Import Packages.
Next, we need to create an object of the Scanner class. We can use the object to take input from the user.

Example: get an entire input from the user

import java.util.Scanner;

class Input {
    public static void main(String[] args) {
    	
        Scanner input = new Scanner(System.in);
    	
        System.out.print("Enter an integer: ");
        int number = input.nextInt();
        System.out.println("You entered " + number);

        // closing the scanner object
        input.close();
    }
}
Output:

Enter an integer: 23
You entered 23
In the example above, we created an object named input of the Scanner class. We then call the nextInt() method of the Scanner class to get integer input from the user.

Likewise, we can use the nextLong(), nextFloat(), nextDouble(), and next() methods to get the user's long, float, double, and string entries, respectively.

Note: We used the close() method to close the object. It is recommended to close the scanner object once the entry is made

Example: Get float, double and String Input

import java.util.Scanner;

class Input {
    public static void main(String[] args) {
    	
        Scanner input = new Scanner(System.in);
    	
        // Getting float input
        System.out.print("Enter float: ");
        float myFloat = input.nextFloat();
        System.out.println("Float entered = " + myFloat);
    	
        // Getting double input
        System.out.print("Enter double: ");
        double myDouble = input.nextDouble();
        System.out.println("Double entered = " + myDouble);
    	
        // Getting String input
        System.out.print("Enter text: ");
        String myString = input.next();
        System.out.println("Text entered = " + myString);
    }
}
Output:

Enter float: 2.343
Float entered = 2.343
Enter double: -23.4
Double entered = -23.4
Enter text: Hey!
Text entered = Hey!
As mentioned, there are several other ways to get user feedback. Find out more about the Scanner

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