[Java] Java Console Input and Output Examples

Java Console Input and Output Examples

In this Java tutorial, learn different ways to read from and write to the system console. A console is generally connected with Java processes which are started using the command-line tool.

If the Java process has started automatically, (for example a background task), the console may not be available for input and output purposes.

1. Java read input from console

By default, to read from system console, we can use the Console class. This class provides methods to access the character-based console, if any, associated with the current Java process. To get access to Console, call the method System.console().

Console gives three ways to read the input:

  • String readLine() – reads a single line of text from the console.
  • char[] readPassword() – reads a password or encrypted text from the console with echoing disabled
  • Reader reader() – retrieves the Reader object associated with this console. This reader is supposed to be used by sophisticated applications.

    For example, Scanner object which utilizes the rich parsing/scanning functionality on top of the underlying Reader.

Java program to read console input with readLine()

Console readLine() method example
Console console = System.console();
 
if(console == null) {
    System.out.println("Console is not available to current JVM process");
    return;
}
 
String userName = console.readLine("Enter the username: ");
System.out.println("Entered username: " + userName);

Program output

Console
Enter the username: lokesh
Entered username: lokesh

Java program to read console input with readPassword()

Console readPassword() method example
Console console = System.console();
         
if(console == null) {
    System.out.println("Console is not available to current JVM process");
    return;
}
 
char[] password = console.readPassword("Enter the password: ");
System.out.println("Entered password: " + new String(password));

Program output

Console
Enter the password:     //input will not visible in the console
Entered password: passphrase

Java program to read console input with reader()

Console reader() method example
Console console = System.console();
         
if(console == null) {
    System.out.println("Console is not available to current JVM process");
    return;
}
 
Reader consoleReader = console.reader();
Scanner scanner = new Scanner(consoleReader);
 
System.out.println("Enter age:");
int age = scanner.nextInt();
System.out.println("Entered age: " + age);
 
scanner.close();

Program output

Console
Enter age:
12
Entered age: 12

2. Java print output to console

The easiest way to write the output data to console is System.out.println() statements. Still, we can use printf() methods to write formatted text to console.

Java program to write to console with System.out.println

System.out.println() method example
System.out.println("Hello, world!");

Program output

Console
Hello, world!

Java program to write to console with printf()

The printf(String format, Object... args) method takes an output string and multiple parameters which are substituted in the given string to produce the formatted output content. This formatted output is written in the console.

경축! 아무것도 안하여 에스천사게임즈가 새로운 모습으로 재오픈 하였습니다.
어린이용이며, 설치가 필요없는 브라우저 게임입니다.
https://s1004games.com

Console printf() method example
String name = "Lokesh";
int age = 38;
 
console.printf("My name is %s and my age is %d", name, age);

Program output

Console
My name is Lokesh and my age is 38

The above listed methods for reading the input and writing output to the console provide alot of flexibility to read inputs in different formats and in different ways.

I will suggest you to play with given code to understand it better.

Happy Learning !!

[출처] https://howtodoinjava.com/java-examples/console-input-output/

 

 

 

 

 

 

본 웹사이트는 광고를 포함하고 있습니다.
광고 클릭에서 발생하는 수익금은 모두 웹사이트 서버의 유지 및 관리, 그리고 기술 콘텐츠 향상을 위해 쓰여집니다.
번호 제목 글쓴이 날짜 조회 수
27 [java][maven] jar 파일 의존성 한번에 다운로드 maven 사용 졸리운_곰 2023.08.24 12
26 Prometheus + Grafana로 Java 애플리케이션 모니터링하기 file 졸리운_곰 2020.12.17 79
25 Blockchain Implementation With Java Code file 졸리운_곰 2019.06.16 108
24 Java 코드로 이해하는 블록체인(Blockchain) 졸리운_곰 2019.06.16 126
23 순수 Java Application 코드로 Restful api 호출 졸리운_곰 2018.10.10 244
22 WebDAV 구현을 위한 환경 설정 file 졸리운_곰 2017.09.24 74
21 [Java] Apache Commons HttpClient로 SSL 통신하기 졸리운_곰 2017.03.27 545
20 JSoup를 이용한 HTML 파싱 졸리운_곰 2017.03.04 100
19 jsoup을 활용해서 Java에서 HTML 파싱하는 방법 정리 file 졸리운_곰 2017.03.04 157
18 NSA의 Dataflow 엔진 Apache NiFi 소개와 설치 file 졸리운_곰 2017.01.23 463
17 wordpress-java-integration 자바와 워드프레스 통합 졸리운_곰 2016.12.30 166
16 Create New Posts in Wordpress using Java and XMLRpc 졸리운_곰 2016.11.14 69
15 자바로 POST 방식으로 통신하기, java httppost 클래스를 활용한 예제 졸리운_곰 2016.11.14 444
14 [Java]아파치 HttpClient사용하기 file 졸리운_곰 2016.11.14 104
13 Building a Search Engine With Nutch Solr And Hadoop file 졸리운_곰 2016.04.21 219
12 Nutch and Hadoop Tutorial file 졸리운_곰 2016.04.21 209
11 Latest step by Step Installation guide for dummies: Nutch 0. file 졸리운_곰 2016.04.21 131
10 Nutch 초간단 빌드와 실행 졸리운_곰 2016.04.21 454
9 Nutch로 알아보는 Crawling 구조 - Joinc 졸리운_곰 2016.04.21 352
8 A tiny bittorrent library Java: 자바로 만든 작은 bittorrent 라이브러리 file 졸리운_곰 2016.04.20 242
대표 김성준 주소 : 경기 용인 분당수지 U타워 등록번호 : 142-07-27414
통신판매업 신고 : 제2012-용인수지-0185호 출판업 신고 : 수지구청 제 123호 개인정보보호최고책임자 : 김성준 sjkim70@stechstar.com
대표전화 : 010-4589-2193 [fax] 02-6280-1294 COPYRIGHT(C) stechstar.com ALL RIGHTS RESERVED