Hello so i am new to javax.swing and i wanted to ask you guys why am i getting this error(i am going to put the exact error after my code). I have tried everything i can find. Thank you guys and im sorry if this is an easy fix i really suck at ruby right now
testGui.rb
# javaSwingHello.rb
require 'java' # Line 2
JFrame = javax.swing.JFrame
JLabel = javax.swing.JLabel
JPanel = javax.swing.JPanel
JButton = javax.swing.JButton
BorderFactory = javax.swing.BorderFactory
BorderLayout = java.awt.BorderLayout
GridLayout = java.awt.GridLayout
count = 1
frame = JFrame.new
panel = JPanel.new
button = JButton.new "Click me"
button.addActionListener self
label = JLabel.new "Number of clicks: 0"
panel.setBorder BorderFactory.createEmptyBorder(70, 70, 20, 70)
panel.setLayout GridLayout.new(0, 1)
panel.add button
panel.add label
frame.add panel, BorderLayout::CENTER
frame.setDefaultCloseOperation(JFrame::EXIT_ON_CLOSE)
frame.setTitle "TEST GUI"
frame.pack
frame.setVisible true
def actionPerformed(event)
count += 1
texttoset = "Number of clicks " + count
label.setText(texttoset)
end
Error( I am getting this when i press the button )
Exception in thread "AWT-EventQueue-0" org.jruby.exceptions.NoMethodError: (NoMethodError) undefined method `+' for nil:NilClass
at testGui.actionPerformed(testGui.rb:26)
more of a Ruby question - local variables won't be copied into a new scope:
def actionPerformed(event)
count += 1
texttoset = "Number of clicks " + count
label.setText(texttoset)
end
count is a local variable for the method (initially nil) thus the failure.
if you're just testing things out you can work-around this using a global:
$count = 1
def actionPerformed(event)
$count += 1
texttoset = "Number of clicks " + count
label.setText(texttoset)
end
that being said do not use globals and rather setup a proper object that will encapsulate the state and 'implement' the actionPerformed inteface.
You did not say, how you are going to use actionPerformed, but one possibility would be make the method a lambda:
count = 1
$ActionPerformed = -> (event) do
count += 1
texttoset = "Number of clicks " + count
label.setText(texttoset)
end
You would have to invoke it as
$ActionPerformed.call(myEvent)
What makes comparison of the expected and actual object quite difficult:
error: -[MyServiceSpec test_ MyServiceSpec__first_object__should_be_an_exact_meter_reading] : expected: <MyClassName: 0x7f8579c67970> {\n actual = 4650;\n expected = 4561;\n meterReadingDate = "2015-10-26 00:00:00 +0000";\n price = "0.05355";\n productType = Electricity;\n}, got: < MyClassName: 0x7f8579c6aed0> {\n actual = 4650;\n expected = 4560;\n meterReadingDate = "2015-10-26 00:00:00 +0000";\n price = "0.05355";\n productType = Electricity;\n}
There's a difference in one value which is hard to find due to this one line output. Printing the same object with "po" in debug makes the output multiline.
Any idea how to make this output multiline?
I'm trying to do Euler project 13:
Work out the first ten digits of the sum of the following one-hundred 50-digit numbers.
list = [37107287533902102798797998220837590246510135740250,
46376937677490009712648124896970078050417018260538,
74324986199524741059474233309513058123726617309629,
91942213363574161572522430563301811072406154908250,
23067588207539346171171980310421047513778063246676,
89261670696623633820136378418383684178734361726757,
28112879812849979408065481931592621691275889832738,
44274228917432520321923589422876796487670272189318,
47451445736001306439091167216856844588711603153276,
70386486105843025439939619828917593665686757934951,
62176457141856560629502157223196586755079324193331,
64906352462741904929101432445813822663347944758178,
92575867718337217661963751590579239728245598838407,
58203565325359399008402633568948830189458628227828,
80181199384826282014278194139940567587151170094390,
35398664372827112653829987240784473053190104293586,
86515506006295864861532075273371959191420517255829,
71693888707715466499115593487603532921714970056938,
54370070576826684624621495650076471787294438377604,
53282654108756828443191190634694037855217779295145,
36123272525000296071075082563815656710885258350721,
45876576172410976447339110607218265236877223636045,
17423706905851860660448207621209813287860733969412,
81142660418086830619328460811191061556940512689692,
51934325451728388641918047049293215058642563049483,
62467221648435076201727918039944693004732956340691,
15732444386908125794514089057706229429197107928209,
55037687525678773091862540744969844508330393682126,
18336384825330154686196124348767681297534375946515,
80386287592878490201521685554828717201219257766954,
78182833757993103614740356856449095527097864797581,
16726320100436897842553539920931837441497806860984,
48403098129077791799088218795327364475675590848030,
87086987551392711854517078544161852424320693150332,
59959406895756536782107074926966537676326235447210,
69793950679652694742597709739166693763042633987085,
41052684708299085211399427365734116182760315001271,
65378607361501080857009149939512557028198746004375,
35829035317434717326932123578154982629742552737307,
94953759765105305946966067683156574377167401875275,
88902802571733229619176668713819931811048770190271,
25267680276078003013678680992525463401061632866526,
36270218540497705585629946580636237993140746255962,
24074486908231174977792365466257246923322810917141,
91430288197103288597806669760892938638285025333403,
34413065578016127815921815005561868836468420090470,
23053081172816430487623791969842487255036638784583,
11487696932154902810424020138335124462181441773470,
63783299490636259666498587618221225225512486764533,
67720186971698544312419572409913959008952310058822,
95548255300263520781532296796249481641953868218774,
76085327132285723110424803456124867697064507995236,
37774242535411291684276865538926205024910326572967,
23701913275725675285653248258265463092207058596522,
29798860272258331913126375147341994889534765745501,
18495701454879288984856827726077713721403798879715,
38298203783031473527721580348144513491373226651381,
34829543829199918180278916522431027392251122869539,
40957953066405232632538044100059654939159879593635,
29746152185502371307642255121183693803580388584903,
41698116222072977186158236678424689157993532961922,
62467957194401269043877107275048102390895523597457,
23189706772547915061505504953922979530901129967519,
86188088225875314529584099251203829009407770775672,
11306739708304724483816533873502340845647058077308,
82959174767140363198008187129011875491310547126581,
97623331044818386269515456334926366572897563400500,
42846280183517070527831839425882145521227251250327,
55121603546981200581762165212827652751691296897789,
32238195734329339946437501907836945765883352399886,
75506164965184775180738168837861091527357929701337,
62177842752192623401942399639168044983993173312731,
32924185707147349566916674687634660915035914677504,
99518671430235219628894890102423325116913619626622,
73267460800591547471830798392868535206946944540724,
76841822524674417161514036427982273348055556214818,
97142617910342598647204516893989422179826088076852,
87783646182799346313767754307809363333018982642090,
10848802521674670883215120185883543223812876952786,
71329612474782464538636993009049310363619763878039,
62184073572399794223406235393808339651327408011116,
66627891981488087797941876876144230030984490851411,
60661826293682836764744779239180335110989069790714,
85786944089552990653640447425576083659976645795096,
66024396409905389607120198219976047599490197230297,
64913982680032973156037120041377903785566085089252,
16730939319872750275468906903707539413042652315011,
94809377245048795150954100921645863754710598436791,
78639167021187492431995700641917969777599028300699,
15368713711936614952811305876380278410754449733078,
40789923115535562561142322423255033685442488917353,
44889911501440648020369068063960672322193204149535,
41503128880339536053299340368006977710650566631954,
81234880673210146739058568557934581403627822703280,
82616570773948327592232845941706525094512325230608,
22918802058777319719839450180888072429661980811197,
77158542502016545090413245809786882778948721859617,
72107838435069186155435662884062257473692284509516,
20849603980134001723930671666823555245252804609722,
53503534226472524250874054075591789781264330331690]
Here is my code:
def countNumbers(list)
value = 0
(0..list.count).each { |y| value += list[y] }
return value
end
puts "#{countNumbers(list)}"
I get: *nil can't be coerced into Bignum* error when I run the code.
The issue is with the range in countNumbers method.
0..list.count returns 0 to 100 with 100 included but list[100] is nil.
Change it to 0...list.count with return 0 to 99.
See the documentation to better understand using .. and ...
I am trying to change one example to take a user input rather than using hard coded values then use those local variables to work out items needed.
So far my code looks like this:
print "Number of cars available today."
cars = gets.chomp()
print "Number of available seats in the car."
space_in_a_car = gets.chomp()
print "Number of drivers available."
drivers = gets.chomp()
print "Number of passagers that need transport."
passangers = gets.chomp
cars_not_driven = #{cars} - #{drivers}
cars_driven = drivers
carpool_capacity = #{cars_driven} * #{space_in_a_car}
average_passanger_per_car = #{passangers} / #{drivers}
print "The number of cars being driven today is #{cars_driven}.\n"
print "The number of cars not being driven today is #{cars_not_driven}.\n"
print "We have #{carpool_capacity} cars available.\n"
print "So we need to carry #{average_passanger_per_car} passangers per car to make sure we can transport everyone.\n"
The code will run without throwing any errors but of course because I am not getting the correct commands in:
cars_not_driven = #{cars} - #{drivers}
cars_driven = drivers
carpool_capacity = #{cars_driven} * #{space_in_a_car}
average_passanger_per_car = #{passangers} / #{drivers}
the only value I am getting in the return is:
print "The number of cars being driven today is #{cars_driven}.\n"
How should I be writing:
cars_not_driven = #{cars} - #{drivers} etc
to get the number of cars_not_driven?
I don't understand very well why you use this #{var} and <br>. If I am right that you want to use plain ruby, this should be the solution:
print "Number of cars available today."
cars = gets.chomp().to_i
print "Number of available seats in the car."
space_in_a_car = gets.chomp().to_i
print "Number of drivers available."
drivers = gets.chomp().to_i
print "Number of passagers that need transport."
passangers = gets.chomp.to_i
cars_not_driven = cars - drivers
cars_driven = drivers
carpool_capacity = cars_driven * space_in_a_car
average_passanger_per_car = passangers / drivers
print "The number of cars being driven today is #{cars_driven}.\n"
print "The number of cars not being driven today is #{cars_not_driven}.\n"
print "We have #{carpool_capacity} cars available.\n"
print "So we need to carry #{average_passanger_per_car} passangers per car to make sure we can transport everyone.\n"
When you use gets Ruby is expecting and returning a String. So variables car, drivers etc are all String.
In order to do integer operation over them, you need to convert them to integers. In Ruby you can do this using .to_i.
Now with that information, try:
cars_not_driven = cars.to_i - drivers.to_i
cars_driven = drivers.to_i
carpool_capacity = cars_driven * space_in_a_car.to_i
average_passanger_per_car = passangers.to_i / drivers.to_i
You can check the class of a variable using .class. Here:
cars = gets.chomp()
10
# => "10"
cars.class
# => String
drivers = gets.chomp()
20
# => "20"
drivers.class
# => String
Now lets add them:
cars + drivers
# => "1020"
Since they are string, + operator is adding two strings to one. Not something you intended. Now try this:
cars.to_i + drivers.to_i
# => 30
I worked up a working code to check if a credit card is valid using luhn algorithm:
class CreditCard
def initialize(num)
##num_arr = num.to_s.split("")
raise ArgumentError.new("Please enter exactly 16 digits for the credit card number.")
if ##num_arr.length != 16
#num = num
end
def check_card
final_ans = 0
i = 0
while i < ##num_arr.length
(i % 2 == 0) ? ans = (##num_arr[i].to_i * 2) : ans = ##num_arr[i].to_i
if ans > 9
tens = ans / 10
ones = ans % 10
ans = tens + ones
end
final_ans += ans
i += 1
end
final_ans % 10 == 0 ? true : false
end
end
However, when I create driver test codes to check for it, it doesn't work:
card_1 = CreditCard.new(4563960122001999)
card_2 = CreditCard.new(4563960122001991)
p card_1.check_card
p card_2.check_card
I've been playing around with the code, and I noticed that the driver code works if I do this:
card_1 = CreditCard.new(4563960122001999)
p card_1.check_card
card_2 = CreditCard.new(4563960122001991)
p card_2.check_card
I tried to research before posting on why this is happening. Logically, I don't see why the first driver codes wouldn't work. Can someone please assist me as to why this is happening?
Thanks in advance!!!
You are using a class variable that starts with ##, which is shared among all instances of CreditCard as well as the class (and other related classes). Therefore, the value will be overwritten every time you create a new instance or apply check_card to some instance. In your first example, the class variable will hold the result for the last application of the method, and hence will reflect the result for the last instance (card_2).