This document covers the content related to variables and system input/output in Java Chapter 2.4.

1. System Input/Output

Until now, we have used functions associated with System.in and System.out for monitor input and output. This can especially be seen in System.out.println.

1.1 System Output

The System.out.println we have used prints a line and moves to a new line. If you do not want to add a newline after the printed content, you can use System.out.print.

Additionally, System.out.printf is provided for printing formatted strings similar to the C language. This function operates in the same manner as the printf function in C. An example of using a format string is as follows:

package study;

public class Hello {
  public static void main(String[] args){
    System.out.printf("My name is %s and I am %d years old." , "Hong Gil-dong", 20);
  }
}

1.2 System Input

There are input functions that receive input from the user. The System.in.read() function reads a single character. However, this function can only read one character at a time, which means it cannot accept strings like "ab" or even Korean characters. The Enter key is processed as both a carriage return and a line feed with two keystrokes.

To address this limitation, the Scanner class is introduced. By creating a Scanner object and using the nextLine() function, you can accept an entire line of input.

package study;

import java.util.Scanner;

public class Hello {
  public static void main(String[] args){
    // Create a Scanner object and store it in sc
    Scanner sc = new Scanner(System.in);
    // Store the read string
    String userInput = sc.nextLine();
    System.out.println(userInput);
  }
}