How to Get Input from User in Java from Command Line : 3 Approach

 

Are you looking for How to get input from user in java from command Line ?

Actually There are three easy and possible ways in java for taking input from user in command line . Lets go one by one .

How to get input from user in java using Bufferedreader Class-

1.1 – String ( input from user in java using Bufferedreader Class ) –

 

//BufferedReader object creation 
BufferedReader readerObj = new BufferedReader(new InputStreamReader(System.in));
 //readLine function for reading string 
String UserInputString = readerObj.readLine(); 
//Print the the String Input System.out.println(UserInputString);

1.2 – Integer  ( input from user in java using Bufferedreader Class)-

Now ervery thing will be same as above . I mean you have to take the input as String and then covert into required Format .Here is the code sample  for how to convert String to Integer in java .

// code for taking Input as String 
 BufferedReader readerObj = new BufferedReader(new InputStreamReader(System.in));
 String UserInputString = readerObj.readLine(); 
// code to convert string into java  
int userInputInteger = Integer.parseInt(userInputString);

Note – You may get run time exception if the input String can not be converted into Integer.For example is user input the string like “23as”  then it is not a valid Integer while parsing . In that situation you may get exception link this –

how to get input from user in java Exception in BufferedReader

1.3-   Float /Double  (input from user in java using Bufferedreader Class)-

In the same way as we did the parsing of String into Integer , We can do it with Float and Double . Here is the Syntax for conversion of String into Float and Double .

//code for taking Input as String 
 BufferedReader readerObj = new BufferedReader(new InputStreamReader(System.in)); 
String UserInputString = readerObj.readLine(); 
//Coverting the String into Double 
double userInputDouble = Double.parseDouble(userInputString);

Complete code for BufferedReader Class Input –

Here is the complete code for – How to get input from user in java from command Line using Buffered Reader Class.

 

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
public class InputExampleUsingBufferedReader {
public static void main (String args[]) throws IOException
{
//BufferedReader object creation
BufferedReader readerObj = new BufferedReader(new InputStreamReader(System.in));
//readLine function for reading string
// Reading data using readLine
String userInputString = readerObj.readLine();
//Print the the String Input
System.out.println(userInputString);
//Coverting the String into Integer
int userInputInteger = Integer.parseInt(userInputString);
System.out.println(" /n Here is coverted Integer from the Input String" +userInputInteger);
//Coverting the String into Double
double userInputDouble = Double.parseDouble(userInputString);
System.out.println(" /n Here is coverted Double from the Input String" +userInputDouble);
//Coverting the String into Float
float userInputFloat = Float.parseFloat(userInputString);
System.out.println(" /n Here is coverted Float from the Input String" +userInputFloat);
}
}

 

How to get input from user in java using Scanner Class –

Here first you need to create Scanner Class object . Once you have the object you may call functions likenextInt() for integer Input and nextLong()for long input etc . Below is the complete example for that .

 

import java.util.Scanner;
public class InputExampleUsingScanner {
public static void main(String args[]) {
//Scanner Object creation
Scanner scannerObj= new Scanner(System.in);
//Integer Input using Scanner 
int userInputInteger=scannerObj.nextInt();
//String Input using Scanner 
String userInputString =scannerObj.nextLine();
/Double Input using Scanner 
Long userInputLong=scannerObj.nextLong();
}
}

How to get input from user in java using Console Class –

In this section before jumping into code part , It is essential to introduce System.class in java . This class is available in (Java.lang) package . You need not to initiate this class .

Now lets jump into code part –

 

//console() function for reading string 
String userInputString = System.console().readLine();

 

hink it will be more clear to see the full example . Specially I am focusing more on the part where I have said , You need not to initiate System.class explicitly .

 

public class UserInputUsingConsoleFunction 
{
 public static void main(String[] args) 
{ 
// How to invoke System.console() method 
String userInputString = System.console().readLine(); 
System.out.println(userInputString);
 } 
}

 

Note – You can not run directly on IDE . You need console to run this code . If you run it on IDE , You will get Exception .

Which One Java user Input method is better –

  1. BufferedReader and console.readLine() are synchronized . Although Scanner is not synchronized .
  2. Syntax wise BufferedReader is little difficult than other two .
  3. You can avoid displaying user input screen with console.readLine()  . So it is more prefer where password or any other confidential information is needed .

Bonus Tips –

Although this article is beneficial in every field of software development with java  because its Core Java Understanding . In case you are more Interested in Data Science with Java , Must read the article –  How a Java Engineer can Transform his career into Data Science | Java for Data Science ?
Thanks

Data Science Learner  Team 

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