Sorting ArrayList Of Type Int - Overloading Efficiency
Feb 11, 2014
I have a case in which I want to sort two types of ArrayLists (using quicksort) and the method originally coded only accepts a String ArrayList. The problem is that now I want to sort an ArrayList of type int but couldn't . . . so I decided to overload the method. Since it looks very ugly to copy and paste the same chunk of code only to change the method signature I wondered if there is a better way to make this method more dynamic and be able to take in different types of ArrayLists.
My code:
private ArrayList<String> sort(ArrayList<String> ar, int lo, int hi){
if (lo < hi){
int splitPoint = partition(ar, lo, hi);
sort(ar, lo, splitPoint);
sort(ar, splitPoint +1, hi);
The operator < is undefined for the argument type(s) java.util.ArrayList<FacebookUser>, java.util.ArrayList<FacebookUser>
For this:
class FriendsComparator implements Comparator<FacebookUser> { @Override public int compare(FacebookUser o1, FacebookUser o2) { int returnValue = 0; if (o1.friends < o2.friends) returnValue = -1; [Code] ....
Same as for the second if condition. How can I fix this exactly? What I'm doing is trying to sort Facebook users by the most to least amount of friends.
we have an Arraylist<Tweet>, and this class is defined as followe: public class Tweet implements Comparable<Tweet>, Serializable. now if we implement the method comparteTo, then will it be sorted automatically? I want to sort this array by any insert.
I have to create a method with the following header :
public static <E extends Comparable<E> > void sort ( ArrayList<E> list , int left, int right)
i also had to create a swap cells method and position of max integer method. and also had to read the preserved data file in with a scanner. I implemented the comparable interface I am having difficulty sorting my list by the area. It has to be in descending order.
Geometric Object class: since it has comparator also am interested if i need to change this?
CODE:
Driver: public static void main(String[] args) throws IOException, ClassNotFoundException { Circle c1 = new Circle (4, "red", false); Circle c2 = new Circle (2, "blue", true); Circle c3 = new Circle (10, "blue", true); Rectangle r1 = new Rectangle (10, 6, "yellow", true); Rectangle r2 = new Rectangle ( 5, 11, "green", true); ArrayList <GeometricObject> list = new ArrayList();
I want to get the max volume from a file that I stored in an arraylist but it don't know if this is the way to do it. also I don't know how to print the method in the main method. here is the method that will get the max volume
public Shape3D maxVolume(ArrayList<Shape3D> shapes ){ Shape3D currentMax; int currentMaxIndex = 0; for ( int i = 1; i < shapes.size(); i++)
[Code] ....
This is my shape3D class
public abstract class Shape3D implements Comparable<Shape3D> { private String type; public double radious; public double height;
Where usually to instantiate and declare variables to be used in a loop. If you declare it outside to be used in the loop it will still be there when the loop is done, never to be used again and is just sitting there taking up memory. However, if you declare it inside the loop, you have the issue of it constantly creating space for said variable, but once it's out of scope it's gone. Is there any advantage performance wise to doing it either way?
I am making an android racing game. I have a method that draws the track to the screen, the map is bigger than the screen so i clip the bitmap and draw it to the screen hence to draw the track I have to get the visible track points and then draw them. I have noticed that when I enable drawing the track the game lags quite a bit but when i disable it is smooth as expected the code is below :
public void drawTrack(Canvas canvas) { if (this.trackPoints != null && this.trackPoints.size() > 0) { // get points, convert back to screen coords and add them to array, // then // use that arraylist<point> below getCurrentVisibleTrack(); counter++; if (this.visibleTrackPoints.size() > 0) {
We have an autosys job running in our production on daily basis. It calls a shell script which in turn calls a java servlet. This servlet reads these files and inserts the data into two different tables and then does some processing. Java version is 1.6 & application server is WAS7 and database is oracel-11g.
We get several issues with this process like it takes time, goes out of memory etc etc. Below are the details of the way we have coded this process.
1. When we read the file using BufferedReader, do we really get a lot of strings created in the memory as returned by readLine() method of BufferedReader? These files contain 4-5Lacs of line. All the records are separated by newline character. Is there a better way to read files in java to achieve efficiency? I couldnt find any provided the fact that all the record lines in the file are of variable length.
2. When we insert the data then we are doing a batch process with statement/prepared statement. We are making one batch containing all the records of the file. Does it really matter to break the batch size to have better performance?
3. If the tables has no indexes defined nor any other constraints and all the columns are VARCHAR type, then which operation will be faster:- inserting a new row or updating an existing row based upon some matching condition?
I am going through Thinking in Java, 4th Ed and I came across the section that talks about overloading variable arguments. I tried out a piece of code from the book. (Method and class names not exactly the same).
public class Varargs { public static void m1(Character... args) { System.out.println("Character");
[code]....
In the above code, the compiler throws an 'Ambiguous for the type varargs' error. The error goes away if the first method is changed to:
public static void m1(char c, Character... args)
why there is ambiguity in the first piece of code and not the second.
I can understand result 3 is because of an upcast from short to int, since FunWithOverloading will not have a overloaded method with short now. However, what is happening with result 4? Shouldn't it call methodA of the subclass with the argument type short? If its because I have declared the reference variable, derived, of the type FunWithOverloading, then how come the first result correctly picks the overloaded method of the sub class?
class FunWithOverloading{ void methodA(int x){System.out.println("Integer method " + x);} void methodA(short x){System.out.println("Short method " + x);} //line 3 } class OverloadedSubClass extends FunWithOverloading{ void methodA(short x){System.out.println("Sub class short method " + x);}
The class Overloading below asks for two names and prints three different greetings. Your task is to write the class methods missing from the class declaration. Methods print the greetings as shown in the example print. The names and parameter types of the needed methods can be checked from the main method because all methods are called there. This exercise also does not require you to copy the source code below to the return field. The method declarations will suffice.
Example output
Type in the first name: John
Type in the second name: Doe
Java Code:
import java.util.Scanner; public class Overloading { public static void main(String[] args) { String firstName, secondName; Scanner reader = new Scanner(System.in);
The class Overloading below asks for two names and prints three different greetings. Your task is to write the class methods missing from the class declaration. Methods print the greetings as shown in the example print.
Hint:The names and parameter types of the needed methods can be checked from the main method because all methods are called there. This exercise also does not require you to copy the source code below to the return field.
The method declarations will suffice.
Example output Type in the first name: John Type in the second name: Doe
********** Hi! ********** Hi, John ********** Hi, John and Doe **********
import java.util.Scanner; public class Overloading { public static void main(String[] args) { String firstName, secondName;
I was told to create a class named Billing that includes three overloaded computeBill methods for a photobook store.
The first method takes the price of the book ordered, adds 8% tax and returns the total due. The second method takes the price of the book, and the quantity, adds tax and returns the total. The final method takes the price, quantity and a coupon discount, adds tax and returns the total.
All of this I have managed fairly well, although I keep getting a strange error at the end of my program that the constructor is undefined. The problem bits of code(the one throwing the errors) are under the comment //Enter values into each of the methods
Code:
package org.CIS406.lab2;
public class Billing { //Declarations double bookPrice; int quantityOrdered; double couponValue;
[Code] ....
My first thought was to create a constructor for each of the methods that I am using...
If you have final int i = 1; short s = 1; switch(s) { case i: System.out.println(i); }
it runs fine. Note that the switch expression is of type short (2 bytes) and the case constant is of type int (4 bytes).My question is: Is the type irrelevant as long as the value is within the boundaries of the type of the switch expression?I have the feeling that this is true since:
byte b = 127; final int i = 127; switch(b) { case i: System.out.println(i); }
This runs fine again, but if I change the literal assigned to i to 128, which is out of range for type byte, then the compiler complains.Is it true that in the first example the short variable and in the second example the byte variable (the switch expressions) are first implicitly converted to an int and then compared with the case constants?
Got a problem with generics, which I'm still pretty new at. Here's a program that compiles fine:
import java.util.ArrayList; import javax.swing.JComponent; public class Experiments { public static void main(String[] args) { ListHolder holder = new ListHolder();
[Code] ....
It's useless, but it compiles. If I change Line 14, however, to add a generic type parameter to the ListHolder class, Line 10 no longer compiles:
import java.util.ArrayList; import javax.swing.JComponent; public class Experiments { public static void main(String[] args) { ListHolder holder = new ListHolder();
[Code] ....
I get this error:
Uncompilable source code - incompatible types: java.lang.Object cannot be converted to javax.swing.JComponent at experiments.Experiments.main(Experiments.java:10)
Apparently, the introduction of the type parameter leaves the compiler thinking that aList is of type Object. I can cast it, like this:
JComponent c = ((ArrayList<JComponent>)holder.aList).iterator().next();
That makes the compiler happy, but why is it necessary? How does adding the (unused) type parameter to the ListHolder class end up making the compiler think the aList member of an instance of ListHolder is of type Object?
I'm trying to parse and compare the content of a zip file. However I'm stuck at what SHOULD be a very simple problem, however I can't seem to find a solution. I have done the following:
ZipInputStream zin1 = new ZipInputStream(fin); ZipEntry ze1 = null; fin2 = new FileInputStream(fileName2); ZipInputStream zin2 = new ZipInputStream(fin2); ZipEntry ze2 = null; //fin.close(); ze1 = zin1.getNextEntry(); ze2 = zin2.getNextEntry();
Which gives me the first entry of each zipfile as a ZipEntry type object. I have tried getting the path of the file (inside the zip file) and using this to create a File type object. This does not seem to work though I get:
Exception in thread "main" java.io.FileNotFoundException: My DocumentsmetadatacoreProperties.xml (The system cannot find the file specified) at java.io.FileInputStream.open(Native Method) at java.io.FileInputStream.<init>(Unknown Source) at java.io.FileReader.<init>(Unknown Source)
And this is because I get a null return from trying to create the File file1 = new File(correctLocation);
I guess I cannot access the file inside a zip file this way. So my question is how can I make a ZipEntry type object into a File type object?
