Right Triangle Pattern - 2

A basic program that gets input rows (Integer) from the user and prints the following pattern.

Input: 5
Output:
 
 x
 o  o
 x  x  x
 o  o  o  o
 x  x  x  x  x

Task: Print the desired star pattern as depicted above.

The filename must have the same name as the public class name, This is to ensure that the Java Virtual Machine (JVM) understands the entry point of the program

To run the program, open your commandline and type the following:

• Without Commandline Arguments

 $ ..\JavaBasic> javac .\RightTriangle2\RightTriangle2.java
 $ ..\JavaBasic> java RightTriangle2.RightTriangle2

• With Commandline Arguments

 $ ..\JavaBasic> javac .\RightTriangle2\RightTriangle2.java
 $ ..\JavaBasic> java RightTriangle2.RightTriangle2 5

RightTriangle2.java

package RightTriangle2;

import java.util.Scanner;

public class RightTriangle2 {
    static char symbol;
    static int rows = 0;

    public static void main(String[] args) {
        if (args.length > 0) {
            if (args.length == 1)
                rows = Integer.parseInt(args[0]);
            else
                System.out.println("[!] Available arguments: [rows (integer)] ");
        } else {
            Scanner scan = new Scanner(System.in);
            System.out.print("[<-] Enter the number of rows: ");
            rows = scan.nextInt();
            scan.close();
        }
        starPrinter(rows);
    } // end of main method

    public static void starPrinter(int rows) {
        System.out.println("\n[->] Output: \n");
        if (rows < 1)
            System.out.println("[!] Number of Rows must be greater than 1.");
        else {
            for (int i = 1; i <= rows; i++) {
                if (i % 2 == 0)
                    symbol = 'o';
                else
                    symbol = 'x';
                for (int j = 1; j <= i; j++)
                    System.out.print(" " + symbol + " ");
                System.out.println();
            }
        }
        System.out.println();
    }
}

Explanation

import java.util.Scanner; : imports Scanner class from java > util package. Scanner is a class that lets you get input form the user. Scanner can take any primitive data type as input from the user.

public static void main(String[] args) : main method/function is the first method that will be executed in any java programs.

String[] args : args is a array of String type. It is used to get commandline arguments for your program.

args.length > 0 : checks whether args is empty or not

System.out.println(); : Prints the String and changes output cursor to next line

Scanner scan = new Scanner ( System.in ); : scan is an object(a special variable that stores the address in RAM/main memory) of the class Scanner. Here scan acts as the variable that has the access to System.in stream (An input stream that connects keyboard input to the program.

scan.nextInt() : gets Integer input from user.

scan.close(); : closes the input stream link/pipe.

public static void starPrinter(int rows) : user defined method that prints the desired star pattern by taking the number of rows from the user as input.