Anyone can explain this program to me?

Question

import java.util.List;
import java.util.LinkedList;
import java.util.Iterator;
public class Lab_02
     public static List getLinesOfText(int m)
{      List lines = new LinkedList();     
          StringBuffer line = new StringBuffer();
          for( int i = 0; i < m; i++ )
{         for( int j = 0; j < m; j++ )           
               line.append( j < i ? " ": Integer.toString(i%10) );
     lines.add(line.toString());
               line.setLength(0);
               return lines;
     public static void main(String args[])
     int n = 15;
               if( args.length > 0 )
               try
     {            n = Integer.parseInt(args[0]);
     catch( NumberFormatException nfe )
     {        String msg = nfe.getMessage();
          System.out.println(msg);
     Iterator lineIterator = getLinesOfText(n).iterator();
     while(lineIterator.hasNext())
          System.out.println(lineIterator.next());

Answer 1

  public static void main(String[] args) {
    int n = 15;
    if( args.length > 0 ) {                     // if an argument was entered
      try { n = Integer.parseInt(args[0]); }    // change it to an int
      catch( NumberFormatException nfe ) {      // if bad format
     String msg = nfe.getMessage();          // print a message
     System.out.println(msg);
//  call getLinesOfText(with the above number, it returns a List),
//  get an iterator for that list, and
//  assign that iterator to lineIterator
      Iterator lineIterator = getLinesOfText(n).iterator();
//  loop through the iterator printing each value
      while(lineIterator.hasNext()) System.out.println(lineIterator.next());
  public static List getLinesOfText(int m) {   // m = count from call above
    List lines = new LinkedList();             // make a LinkedList, assign to lines
    StringBuffer line = new StringBuffer();    // make a StringBuffer, assign to line
    for( int i = 0; i < m; i++ ) {             // loop m times
      for( int j = 0; j < m; j++ ) {           // for each value of i, loop m times
// append either a space or the string representation of i modulo 10
// to the StringBuffer depending on whether j is less that i
// (modulo = remainder after division by 10)
     line.append( j < i ? " ": Integer.toString(i%10) );
// Add the string representation of line (a StringBuffer) to the linkedlist lines
      lines.add(line.toString());
// Clear the StringBuffer
      line.setLength(0);
// return the linked list
    return lines;
  }