String split and NumberFormatException

Here is one interesting catch

I was trying to convert a string with spaces into various subparts

So i used split method and then tried to convert the individual values into int

While parsing int values i was getting NumberFormatException

That seems very strange at first instance but yes i got it.

After careful notice i found that

19 String[] input = line.split("\\s+");
20 System.out.println(input[0]);
21 int withdrawl = Integer.parseInt("input[0]");

Line 21 already had " " quotes inserted in array generated by the split method

So just

19 String[] input = line.split("\\s+");
20 System.out.println(input[0]);
21 int withdrawl = Integer.parseInt(input[0]);

without quotes was enough to parse the value

The javadoc for split method explains more

The string "boo:and:foo", for example, yields the following results with these expressions:

Regex Result
: { "boo", "and", "foo" }
o { "b", "", ":and:f" }

read the program input from text file

How to set and read the program input from text file instead of keyboard

Other day i was trying to take part in some online programming tests and generally we have to give our program which is compliant to certain guidelines.

One of them is that input has to be given from keyboard.

For testing locally i suggest that you can make one text file to give input all in one go

Some thing like

System.setIn(new FileInputStream(

This will set the to the text file specified and you can see the output in console.

Happy Programming

Useful link

Use BufferedReader to read line by line

InputStreamReader in = new InputStreamReader(;
BufferedReader br = new BufferedReader(in);

String line ;
while ((line = br.readLine()) != null){

Earlier i was doing one mistake

invoking readLine() both for checking null and for printing so as a effect the values were skipped and alternate values were being printed. This is due to fact that readLine was called two times and one value was being skipped

Useful resource

Invalid escape sequence (valid ones are \b \t \n \f \r \" \' \\ )

Exception in thread "main" java.lang.Error: Unresolved compilation problem:
Invalid escape sequence (valid ones are \b \t \n \f \r \" \' \\ )

This error comes when we give path


instead of


We should escape the backslash with \


Programming problem at

We have a loud talking parrot. The "hour" parameter is the current hour time in the range 0..23. We are in trouble if the parrot is talking and the hour is before 7 or after 20. Return true if we are in trouble.
parrotTrouble(true, 6) → true
parrotTrouble(true, 7) → false
parrotTrouble(false, 6) → false

My Solution

First i wrote

public boolean parrotTrouble(boolean talking, int hour) {
return false;

if((talking) && ( (hour<7)||(hour>20) ) )
return true;


I got error that

Error:	public boolean parrotTrouble(boolean talking, int hour) {
This method must return a result of type boolean

Possible problem: the if-statement structure may theoretically
allow a run to reach the end of the method without calling return.
Consider using a final else {... to ensure that return is always called.


public boolean parrotTrouble(boolean talking, int hour) {
return false;
return ((talking)&&( (hour<7)||(hour>20) ) );

The official solution was

public boolean parrotTrouble(boolean talking, int hour) {
return (talking && (hour < 7 || hour > 20));
// Need extra parenthesis around the || clause
// since && binds more tightly than ||
// && is like arithmetic *, || is like arithmetic +


Comparison and Lessons

I see that the official solution was too clean , i did extra smartness but straight away saying false if parrot is not talking. I was trying to avoid further checks. But yes official code looks good.

The main issue of missing return in first try.

We need to return always something as per function definition.

The else was missing from earlier code snippet


Programming problem at

Given an int n, return the absolute difference between n and 21, except return double the absolute difference if n is over 21.
diff21(19) → 2
diff21(10) → 11
diff21(21) → 0

My Solution

First i wrote

public int diff21(int n) {
  int absDiff = java.Math.abs(n-21);
  absDiff =  2*absDiff;
  return absDiff;


It gave error that java.Math cannot be resolved to a type. Then i realized i should not use java build in packages

Then i modified correct the code as

public int diff21(int n) {
  int absDiff = n-21;
  if (absDiff < 0 )
  absDiff = (-1)*absDiff;
  absDiff =  2*absDiff;
  return absDiff;


After i read the coding rules ( see Comparison and Lessons below ) , i realized that packages are allowed to be imported

However my mistake was different , i wrote wrong java class package.

The revised correct code with build in function of abs is

public int diff21(int n) {
  int absDiff = java.lang.Math.abs(n-21);
  absDiff =  2*absDiff;
  return absDiff;


The official solution was


public int diff21(int n) {
if (n <= 21) {
return 21 - n;
} else {
return (n - 21) * 2;

Comparison and Lessons

I read the coding rules for CodingBat website (  The java.util package is included in all the problems

My second mistake was to use the wrong java.lang.Math package ( i used java.Math )

Other thing which i noticed specific to CodingBat is below

If the method takes a String or array argument, those arguments will not be passed in a null. However, the empty String or array is still a valid case unless the problem statement specifically says otherwise.

Lessons learnt to remember the java Math class package


Programming problem at

Given two int values, return their sum. Unless the two values are the same, then return double their sum.
sumDouble(1, 2) → 3
sumDouble(3, 2) → 5
sumDouble(2, 2) → 8

My Solution

public int sumDouble(int a, int b) {

return 2*(a+b);

The official solution was

public int sumDouble(int a, int b) {
// Store the sum in a local variable
int sum = a + b;

// Double it if a and b are the same
if (a == b) {
sum = sum * 2;

return sum;

Comparison and Lessons

Missed semi colons in first run , always check sytax errors


Programming problem at

We have two monkeys, a and b, and the parameters aSmile and bSmile indicate if each is smiling. We are in trouble if they are both smiling or if neither of them is smiling. Return true if we are in trouble.
monkeyTrouble(true, true) → true
monkeyTrouble(false, false) → true
monkeyTrouble(true, false) → false


My Solution

Both smiling and both not smiling , that is both true and both false points my brain towards the XOR gate

First i wrote

return (aSmile ^ bSmile );

which gave result exatly opposite to what was required , so i read the problem again

i had to change the code with

return !(aSmile ^ bSmile );

The complete solution is


public class monkeyTrouble {
    public boolean monkeyTrouble(boolean aSmile, boolean bSmile) {
        return !(aSmile ^ bSmile);


The official solution was


public boolean monkeyTrouble(boolean aSmile, boolean bSmile) {
if (aSmile && bSmile) {
return true;
if (!aSmile && !bSmile) {
return true;
return false;
// The above can be shortened to:
// return ((aSmile && bSmile) || (!aSmile && !bSmile));
// Or this very short version (think about how this is the same as the above)
// return (aSmile == bSmile);

Comparison / Analysis

Lesson learnt is to read the problem carefully and to retest your solution with dry run for possible outputs. I am going to write unit tests for testing the programs in future

I found one website which explain all the logical operators in Java


Programming problem at

The parameter weekday is true if it is a weekday, and the parameter vacation is true if we are on vacation. We sleep in if it is not a weekday or we're on vacation. Return true if we sleep in.
sleepIn(false, false) → true
sleepIn(true, false) → false
sleepIn(false, true) → true


My Solution

public class SleepIn {

    public boolean sleepIn(boolean weekday, boolean vacation) {
        if ((weekday == false) || (vacation == true))
            return true;
            return false;



The official solution was


public boolean sleepIn(boolean weekday, boolean vacation) {
if (!weekday || vacation) {
return true;
} else {
return false;
// This can be shortened to: return(!weekday || vacation);



I tried to do it too childish way , comparing booleans :P

Websites for improving programming and algorithms skills

Bunch of resources for improving programming skills by practice and participating in online competitions

Online code practice which shows the right solution straight away. The best part which i like the most is that you can type your code into the text pad on website and see its output

Here you will find hundreds of problems used in the ACM-ICPC Regional's and World Finals. You can submit your sources in a variety of languages, trying to solve any of the problems available in database.

New location is

SPOJ – Sphere Online Judge – is a problem set archive, online judge and contest hosting service accepting solutions in many languages.

This website has lots of programming contests

Project Euler is a series of challenging mathematical/computer programming problems that will require more than just mathematical insights to solve. Although mathematics will help you arrive at elegant and efficient methods, the use of a computer and programming skills will be required to solve most problems.

Participate in programming competitions , practice online questions , participate in online discussions

the USA Computing Olympiad, training pages and online contests.

The USACO 2011 December contest runs from December 9 through December 12. Click Here for further details.

2011-2012 Schedule

Nov 11-14: November Contest
Dec 9-12: December Contest
Jan 6-9: January Contest
Feb 3-6: February Contest
Mar 2-5: March Contest
April: US Open
June: Training Camp
September: IOI 2012 in Milan, Italy

IITKGP Annual Algorithms and Programming contest

Bitwise 2011 was a great success with participation from 3200 teams from over 80 countries.

Any one around the world (except students of IITKGP CSE department) can participate in the contest

Puzzles for solving posted by Facebook



Other Resources

A website having calendar which has dates for coding contests around the world

New line character / OS dependence

The new line character depends on your OS \n for Unix, \r\n for Windows and \r for old Macs

Always use


To find out OS specific line separator instead of judging yourself and hard coding it.

This error can lead to many bugs in system

Katya karoon lyrics meaning

I was asked by my Non punjabi friends about meaning of Katya karoon , the famous song from Rockstar . Thought to translate full.

Kateya Karoon is an old punjabi folk song- The women in old days used to make cotton on the spinning feel . Still this is common time pass in villages but not in cities.  Group of ladies join and sing , talk things of here and there.

Often they sing for for their husbands or lovers..

Following is the detailed analysis

Ting ling ling ling ting ling ling ling >>>> Punjabi rhyme sort of kids do this often
Ting ling ling ling ting ling ling

Kateya karoon kateya karoon >>>> I will spin the cotton wheel ,

Tera roon kateya karoon >>>> Girl is saying to his beloved i will spin your cotton >>> roon means cotton
Tera roon tera roon tera roon roon roon roon roooon  >>>> tera means yours
Saari raati kateya karun  >>> I spin your cotton all night >>>> literal means in your thoughts all night
Kateya karoon kateya karoon
Sari raati kateya karoon
Saara din sochhan vich langhda >>>>> The entire day is spent in this thought
Tere lai hun jiyun te marun  >>>>> I shall live and die for you
Eh tan mera charkha hove  >>>>> My body will be the spinning wheel
Hove ulfat yaar di chittaa roon   >>>>>> And let the love of my beloved be pure cotton
Nachdi phiroon tapdi phiroon >>>>> Let me dance let me fly jumping all around
Keeli mai napdi phiroon >>> Let me be in ecstasy , full speed no stop :P   >>>>> keeli napdi phiroon is often used in punjabi to do things fast
Hadh karoon, hadh karoon >>>>  Crossing all boundaries all barriers
Hadh karoon roon roon roon rooooon
Yaara bulle luteya karoon  >>>>>  I will enjoy full

Mainu darr hun naiyo jag da  >>>>>> Now I dont fear this world
Tere lai hun jiyun te maroon   >>>>> I shall live and die for you
Mai saari raat kateya kateya karoon....




The one more thing which you might be interested

In song Nadaan parindey there are few lines written by Sheik farid who was
a 12th-century Sufi preacher and saint of the Chishti Order of South Asia.

IF you listen song below from time 4.06 min

You can listen following lines

The original lines are as follows  ( In Punjabi with english translation)




English transliteration

kaga karang dhandolya sagla khaya maas

eh do naina mat chuho pir dekhan ki aas

The image below says all about feelings behind these original lines. 



Although film people have copied and modified the lines to make suitable for the film but

i just wanted to share the original person behind those lovely lines

The bani ( text ) written by Sheik farid has been incorporated into Guru Granth Sahib ( the holy book of Sikhs)