Java Program to take input from user through command-Line Argument.
Objective
Write a Java program to read input directly from Command-Line Arguments.
Algorithm / Approach
- In the
main(String[] a)method, access the arraya(orargs). - Read the first argument at index 0 (
a[0]) as a String name. - Read the second argument at index 1 and convert it to an int using
Integer.parseInt(a[1]). - Read the third argument at index 2 and convert it to a double using
Double.parseDouble(a[2]). - Print the variables.
InputDemo.java
class InputDemo{
public static void main(String[] a)
{
String n = a[0];
int age = Integer.parseInt(a[1]);
double m = Double.parseDouble(a[2]);
System.out.println("Name- "+n);
System.out.println("Age- "+age);
System.out.println("Marks- "+m);
}
}Expected Output
// Run as java InputDemo Alok 24 73.4 Name- Alok Age- 24 Marks- 73.4
Explanation of the Program
- Command-line arguments allow you to pass data into a Java program at the exact moment you run it from the terminal (e.g.,
java InputDemo Alok 24 73.4). - The JVM automatically takes those space-separated values and packs them into the
String[]array parameter of the main method. - Because everything from the command line is strictly considered text (String), you must use wrapper classes like
IntegerandDoubleto parse the text back into numbers if you want to do math with them.
Complexity
Time Complexity
O(1)
Space Complexity
O(1)
