Scanner Class and Output in Java

The Scanner class is widely used in Java to take user input, and Java provides three main methods (print(), println(), and printf()) for displaying output effectively.

Scanner Class in Java

Common Methods of Scanner

Before using these methods, create a Scanner object.

1. Import the class:
   import java.util.Scanner;
2. Create object wherever needed:
   Scanner sc = new Scanner(System.in);
3. Call methods to take input:
   int n = sc.nextInt();
   String name = sc.next(); or String name = sc.nextLine();

Example: Scanner Input

import java.util.Scanner;  // Import the Scanner class from java.util package

class ScannerDemo {  
    public static void main(String args[]) {  
        // Create a Scanner object to read input from keyboard
        Scanner sc = new Scanner(System.in);        
        
        // Prompt the user to enter a name
        System.out.print("Enter Name:");  
        String name = sc.next();  // Read a single word string from user input

        // Prompt the user to enter an integer ID
        System.out.print("Enter ID:");  
        int id = sc.nextInt();  // Read an integer from user input

        // Prompt the user to enter a salary
        System.out.print("Enter Salary:");  
        double sal = sc.nextDouble();  // Read a double value from user input

        // Print a separator
        System.out.println("----------"); 

        // Display the entered values
        System.out.println("ID: " + id);  
        System.out.println("Name: " + name);  
        System.out.println("Salary: " + sal);  

        // Close the Scanner object to free resources
        sc.close();  
    }  
}
                        

Enter Name:Ayan
Enter ID:123
Enter Salary:20000
----------
ID:123
Name:Ayan
Salary:20000.0
                        

Scanner sc = new Scanner(System.in);

System.out.print("Enter age: ");
int age = sc.nextInt();

System.out.print("Enter full name: ");
String fullName = sc.nextLine(); // reads leftover newline

System.out.println("Age: " + age);
System.out.println("Name: " + fullName);

sc.close();
    

Enter age: 25
Enter full name: 
Age: 25
Name: 
    

Scanner sc = new Scanner(System.in);

System.out.print("Enter age: ");
int age = sc.nextInt();
sc.nextLine(); // consume leftover newline

System.out.print("Enter full name: ");
String fullName = sc.nextLine();

System.out.println("Age: " + age);
System.out.println("Name: " + fullName);

sc.close();
    

Enter age: 25
Enter full name: Alice Johnson
Age: 25
Name: Alice Johnson
    

Output Methods: print, println, and printf:

In Java, there are several ways to output data to the console:

• System.out.print() → Prints text on the same line without moving to a new line.
• System.out.println() → Prints text and moves the cursor to a new line after output.
• System.out.printf() → Prints formatted text using format specifiers, similar to C's printf. Example specifiers: %d (integer), %f (floating-point), %s (string).
• To start a new line in printf, use %n instead of \n for platform-independent newline.

System.out.print("Hello, ");  // stays on the same line
System.out.println("world!"); // moves to next line after printing
System.out.println("Bye");            

Hello, world!
Bye
            

%[argument_index$][flags][width][.precision]conversion

// Print integer with width and zero-padding
System.out.printf("ID: %05d%n", 42); // Output: ID: 00042

// Print floating-point with 2 decimal places
System.out.printf("Price: %.2f%n", 123.456); // Output: Price: 123.46

// Print string left-aligned within 10 characters
System.out.printf("Name: %-10s End%n", "Alice"); // Output: Name: Alice      End

// ISO and custom date/time formatting
java.util.Date now = new java.util.Date();
System.out.printf("ISO date: %tF%n", now);           // yyyy-MM-dd
System.out.printf("Time: %tT%n", now);               // HH:mm:ss
System.out.printf("Custom: %1$td/%1$tm/%1$tY %1$tR%n", now); 
// Note the reuse of the 1st argument via %1$...
    

Next: Java Type Casting

java.util.Date now = new java.util.Date();
System.out.printf("ISO date: %___%n", now);

int x = 5;
System.out.____("Value: %d%n", x);

int age = sc.nextInt();
// fix here
String name = sc.nextLine();

Scanner sc = new Scanner(System.in);

Scanner sc = new Scanner(System.in);
String line = sc._____();