Ashwin Rao

I was reading about slicing a list in python. All was well until I started the next topic that said there was a third parameter to the slicing called as step. I understood that except for why does the code below print the shoppingList in the reverse order. Can anyone help me? Thanks!
shoppingList = ['apple','orange','banana'] print shoppingList[::-1]

Closing the writer first flushes it and then closes it. So I guess it would have worked if I had just flushed it.

I had forgotten to close the writer!!
After I added writer.close() I got the output! Sorry for the trouble!

Hi,
I'm trying to find out the minimum scalar product of a given two vectors. I've succeeded in my attempt to find out the minimum scalar product. I found the question here. I'm trying to solve the small input. My program calculates the minimum scalar product for all 1000 cases but is only writing 845 of them to the file. I don't understand what's the problem. I think it may have something to do with FileWriter. Any help is much appreciated.
My code is given below:
import java.io.*; import java.util.*; class MinimumScalarProduct { public static void main(String[] args) { try { File inputFile = new File("A-small-practice.in"); FileReader reader = new FileReader(inputFile); BufferedReader bReader = new BufferedReader(reader); FileWriter writer = new FileWriter("Output.txt"); int numberOfCases = Integer.parseInt(bReader.readLine()); StringBuilder output= new StringBuilder(); for(int i = 0; i < numberOfCases; i++) { int lengthOfTheTwoArrays = Integer.parseInt(bReader.readLine()); ArrayList<Integer> arrayOne = new ArrayList<Integer>(); String arrayOneOfString = bReader.readLine(); stringToArrayList(arrayOneOfString,arrayOne); ArrayList<Integer> arrayTwo = new ArrayList<Integer>(); String arrayTwoOfString = bReader.readLine(); stringToArrayList(arrayTwoOfString,arrayTwo); Collections.sort(arrayOne); Collections.sort(arrayTwo); int count = 0; count = arrayTwo.size() - 1; long scalarProduct = 0; for(int j = 0; j < arrayOne.size(); j++) { scalarProduct += arrayOne.get(j) * arrayTwo.get(count--); } writer.write("Case #"+(i + 1)+": "+scalarProduct+"\n"); } } catch (Exception e) { e.printStackTrace(); } } public static void stringToArrayList(String array, ArrayList<Integer> integerArray) { String [] individualStrings = array.split(" "); for (String string : individualStrings) { integerArray.add(Integer.parseInt(string)); } } }

Consider the code below:
class TestClass{ public void method() { System.out.println("Method with no parameters"); } public void method(int a) { System.out.println("Inside a method with one parameter"); } }

Now in main if you write:
TestClass obj = new TestClass(); obj.method(); obj.method(2);

Even before you execute the program the compiler knows which method within the class is gonna be called. Hence the JVM does not have anything to decide at run-time. It already knows which method has to be called based on the arguments. I don't think you can call this compile time binding because the TestClass object is not created until and unless you "run" the program. Whenever you think about something related to objects think "run-time" whenever something is related to static stuff think "compile-time".

Also I want to add one more thing.. a class cannot be marked private. A class can only be marked public,abstract or final.

I think you're confusing Java with C# or C++. Java does not offer operator overloading i.e you cannot define the way operators work on different types.
static functions exist before any objects are created. So you can call a static method before you create any objects of that class as shown below:
class TestClass { public static void method() { System.out.println("Inside TestClass"); } } public class MainClass { public static void main(String [] args) { TestClass.method(); } }

However you need to remember that static methods behave differently than instance methods when involved with inheritance and polymorphism:

class SuperClass { public static void method() { System.out.println("Inside SuperClass"); } } class SubClass extends SuperClass { public static void method() { System.out.println("Inside SubClass"); } }

Now inside main if you write something like this: SuperClass obj = new SubClass(); obj.method();
It would print "Inside SuperClass" instead of "Inside SubcCass". Static methods are not involved in polymorphism!
Hope this helped!!

Here you create an array: Dog[] myDogs = new Dog[3];
Arrays have some built-in superpowers!
"length" is one of them. This "length" variable stores the max. length of the array. In this case it stores 3.

int x = 0; while (x < myDogs.length){ // In this statement you compare the current value of x (which is 0 the first time, //1 the second time and so on) with 3 i.e value of length variable for myDogs array. myDogs[x].bark(); x = x + 1; }

Here's what I think: You need to create a new Person object every time you loop through your while() loop in the main function. To that new object you have to set the name and id fields and then add that object to the list. That way you have a list of Person objects for your list.

Here's what I think is happening. Correct me if I'm wrong:

When you call tst.addAll(); count is incremented by 1 and control goes to the super class version of addAll() as is specified by super.addAll(); but inside the addAll() method of the superclass when you call the add() method it actually calls the overridden add() method in the subclass because the object through which we called it was a subtype.

Am I right? :|

And what CB means by transient sum is that you don't actually need to store the sum of A and B in a seperate variable. You can do something like this return (a + b);
Also the variables A and B inside the main() method have NO RELATIONSHIP to the variables named A and B inside AddAandB. Setting A inside main() does not set A in AddAandB. The two are different. You need to set the A and B inside AddAandB for your program to work. To set them you can pass values through the constructor: setSumAandB(double NumberA, double NumberB).
Hope I helped you out!

Inside the api folder I do not have index.html I have the following folders:

java
javax
org
resources

I actually did download the Java API docs but I don't have a clue how to use them offline..I always end up going to the online docs. Can anyone please explain to me how to use the offline docs?
Thanks!

There is no passage. It written as just one sentence or point and it goes like this:

Only static variables and methods can be accessed as part of the call to super() or this().(Example:super(Animal.NAME) is OK, because NAME is declared as a static variable)

I'm preparing for the OCA 7 exam. I learnt from the OCA 7 book by K&B that you are only allowed to access static variables and methods as a part of the call to super() or this(). I think I would find it easier to understand if they had given a complete example but they just gave (super(Animal.NAME); // OK because NAME is static.) but I am not finding the complete code in the book. So if anyone could give a complete example I would be really grateful. Also another query..Is this actually used in real-world programs?