Acquisition of input contents using Scanner (Java)

What is Scanner

An external library for "entering" a value into the console and using that value in your program. This article describes how to receive a string and how to receive a number.

How to receive as a string

The procedure for receiving a character string is as follows.

1. Load the library
2. Scanner initialization
3. Processing to receive input contents

Loading the library

In order to use Scanner, a description for loading an external library is required. First, add the description of import java.util.Scanner; above the class definition.

Main.java

import java.util.Scanner;

class Main {
  public static void main (String[] args) {
    System.out.print("name:");
  }
}

Scanner initialization

Next, add the description Scanner scanner = new Scanner (System.in); to initialize the Scanner. The Scanner is initialized with new Scanner (System.in) and assigned to the variable scanner.

Main.java

import java.util.Scanner;

class Main {
  public static void main (String[] args) {
    Scanner scanner = new Scanner(System.in);
    System.out.print("name:");
  }
}

Processing to receive input contents

Finally, add the description String name = scanner.next () ;. You can substitute the character string entered in the variable name by writing scanner.next ().

Main.java

import java.util.Scanner;

class Main {
  public static void main (String[] args) {
    Scanner scanner = new Scanner(System.in);
    System.out.print("name:");
    String name = scanner.next();
    System.out.println("Hello" + name + "Mr.");
  }
}

How to receive numerically

The procedure for receiving numerical values is also as follows, but 1 and 2 are omitted because there is a common part with the procedure for receiving numerical strings.

1. Load the library
2. Scanner initialization
3. Processing to receive input contents

Processing to receive input contents

We will add a description to receive numerical values in the following file. (Steps 1 and 2 have been completed)

Main.java

import java.util.Scanner;

class Main {
  public static void main(String[] args) {
    Scanner scanner = new Scanner(System.in);
    
    System.out.print("age:");
    
    System.out.print("height(m)：");
    
  }
}

To receive the age value int age = scanner.nextInt(); Add the description of. The data type is specified by writing nextInt () as a difference from the procedure for receiving as a character string. Note that if you write nextString () etc. when receiving as a character string, an error will occur.

Main.java

import java.util.Scanner;

class Main {
  public static void main(String[] args) {
    Scanner scanner = new Scanner(System.in);
    
    System.out.print("age:");
    int age = scanner.nextInt();
    
    System.out.print("height(m)：");
    double height = scanner.nextDouble();

  }
}