How to get input via command line in Java? [closed]

Answer 1

The Scanner class was implemented in Java 5.0 to make getting input easier:

Scanner input = new Scanner(System.in) the System.in will allow for console input.

Scanner sc = new Scanner(System.in);
int i = sc.nextInt();
/* will wait for input then assign it to the variable,
 * in this case it will wait for an int.
 */
System.out.println(i); // will print the variable

https://docs.oracle.com/javase/7/docs/api/java/util/Scanner.html

Answer 2

You might want to use the Scanner class: java.util.Scanner

The basic setup is simple:

Scanner scan = new Scanner(System.in);
int number = scan.nextInt();

This sets up a scanner object and makes the scanner get an integer from the default input stream. However, this doesn't check to see if the user entered "good data". It will cause errors if the user enters anything other than a number. You might want to include a loop until the user enters valid data.

Here's the same code, but with error checking:

Scanner scan = new Scanner(System.in);
boolean validData = false;
int number=0;
do{
    System.out.println("Enter a Number");
    try{
        number = scan.nextInt();//tries to get data. Goes to catch if invalid data
        validData = true;//if gets data successfully, sets boolean to true
    }catch(InputMismatchException e){
        //executes when this exception occurs
        System.out.println("Input has to be a number. ");
    }
}while(validData==false);//loops until validData is true

This program will ask the user to enter a number. If the user enters bad data, an InputMismatchException is thrown, taking the program to the catch clause and skiping setting validData to true. This loops until valid data is entered.

Hope this helps.

Answer 3

Yea, System.in will work fine for a small number of predictably entered commands. Apache has a nice little tool if you want a more pro/robust mechanism.

See: http://commons.apache.org/proper/commons-cli/

Answer 4

Are you looking for this? As you asked about getting input via command line so if you run your java program via command line and want to pass it some inputs, they are received by args parameter in main. look here

Echoing Command-Line Arguments

The Echo example displays each of its command-line arguments on a line by itself:

public class Echo {
    public static void main (String[] args) {
        for (String s: args) {
            System.out.println(s);
        }
    }
}