Input and Output : MCQs & PYQs with Explanation

Option A

In Java, System.out.println("Hello World!") is used to print messages to the console.

Option B

In Java, System.out is the standard output stream used to display information on the console. The out variable is a static field of the System class, and it refers to an object of the PrintStream class. Therefore, methods such as print(), println(), and printf() can be used with System.out.

Option A

In Java, the format() method of the PrintStream class is used to print formatted output. Since System.out refers to an object of the PrintStream class, we can use System.out.format() to display values in a specified format.

public class FormatExample
{
    public static void main(String args[]) 
    {
        String name = "Suresh Kulahry";
        int marks = 85;
        double percentage = 85.50;
        System.out.format("Name: %s\n",name);
        System.out.format("Marks: %d%n", marks);
        System.out.format("Percentage: %.2f", percentage);
    }
}

Here:

• The %s is used for a string
• The %d is used for an integer.
• The %.2f is used to display a floating-point value with two digits after the decimal point. The %n is used to move to the next line. We can also use \n instead of %n.

Common Format Specifiers Used with System.out.format():

Note:
The format specifiers such as %d, %f, %s, %c, etc. are not interpreted by print() or println(). They are specifically used with methods such as format() and printf().

Option D

In Java, the Scanner class is commonly used to read input from the standard input, which is usually the keyboard. It provides convenient methods for reading different types of primitive data, such as int, double, float, long, and boolean. 
For example, nextInt() reads an integer, nextDouble() reads a double value, and nextBoolean() reads a Boolean value.
The Scanner class, available in the java.util package, provides different methods for reading input from the keyboard or other input sources. The Scanner class provides different types of methods, they are:

The next() stops reading when it encounters whitespace, whereas nextLine() reads the complete line, including spaces.

import java.util.Scanner;
public class ScannerMethods
{
    public static void main(String args[])
    {
        Scanner sc = new Scanner(System.in);
        System.out.print("Enter Name ");
        String name = sc.nextLine();
        System.out.print("Enter City: ");
        String city = sc.next();
        System.out.print("Enter Age: ");
        int age = sc.nextInt();
        System.out.print("Enter Mobile Number: ");
        long mobile = sc.nextLong();
        System.out.print("Enter Salary: ");
        double salary = sc.nextDouble();
        System.out.print("Are You a Student? (true/false): ");
        boolean student = sc.nextBoolean();
        System.out.println("Your Details");
        System.out.println("Name : "+name);
        System.out.println("City :"+city);
        System.out.println("Age : "+age);
        System.out.println("Mobile : "+mobile);
        System.out.println("Salary : "+salary);
        System.out.println("Student :"+student);
        sc.close();
    }
}
OUTPUT
Enter Name Suresh Kulahry
Enter City: Jaipur
Enter Age: 31
Enter Mobile Number: 9828121018
Enter Salary: 78965.58
Are You a Student? (true/false): true
Your Details
Name : Suresh Kulahry
City :Jaipur
Age : 31
Mobile : 9828121018
Salary : 78965.58
Student :true

Option C

In Java, to read input from the user, we commonly use the Scanner class, which is part of the java.util package. First, a Scanner object is created using new Scanner(System.in), which connects the scanner to standard input like keyboard.
The Scanner class provides several methods to read different types of data. To read an integer, the correct method is nextInt().

Option C

Java provides the Scanner class to take input from the keyboard. It is available in the java.util package. The Scanner class provides different methods for reading different types of input. For example, nextInt() is used to read an integer, while nextLine() is used to read a complete line of text.
In the given code, suppose the user enters 55 and presses Enter. The nextInt() method reads the integer 55 and stores it in a. However, nextInt() does not read the Enter key (line separator) after the number. That line separator remains in the input.
When sc.nextLine() is executed, it reads the remaining part of the current line up to the Enter key. Since there is nothing between 55 and the Enter key, nextLine() reads an empty line and returns an empty string "".
Therefore, the values are, a=55 and str="".
Note:
It is important to understand that "" and null are different. An empty string "" is a String containing zero characters, whereas null means that a reference does not refer to any object. In this case, nextLine() returns an empty string, not null.

Option C

Java provides two main types of I/O streams, byte-oriented streams and character-oriented streams.

• Byte-oriented streams are mainly used for handling raw binary data, such as images, audio, video, and other binary files. 
• Character-oriented streams are designed to work with text data, such as letters, words, and sentences.

The FileReader class is a character-oriented class. It is used to read character data from a file and is based on the Reader class hierarchy.