I am totally new to Java. What is the purpose of this method?
Flow of the int x=3; like where does the 3 go step by step?
Passing Primitive Data Type Arguments (from oracle java tutorials)
Primitive arguments, such as an int or a double, are passed into methods by value. This means that any changes to the values of the parameters exist only within the scope of the method. When the method returns, the parameters are gone and any changes to them are lost. Here is an example:
public class PassPrimitiveByValue {
public static void main(String[] args) {
int x = 3;
// invoke passMethod() with
// x as argument
passMethod(x);
Primitive arguments, such as an int or a double, are passed into methods by value. This means that any changes to the values of the parameters exist only within the scope of the method. When the method returns, the parameters are gone and any changes to them are lost.
Reference data type parameters, such as objects, are also passed into methods by value. This means that when the method returns, the passed-in reference still references the same object as before. However, the values of the object's fields can be changed in the method, if they have the proper access level.For example, consider a method in an arbitrary class that moves Circle objects:
public void moveCircle(Circle circle, int deltaX, int deltaY) { // code to move origin of // circle to x+deltaX, y+deltaY circle.setX(circle.getX() + deltaX); circle.setY(circle.getY() + deltaY);
// code to assign a new // reference to circle circle = new Circle(0, 0); }
Let the method be invoked with these arguments: moveCircle(myCircle, 23, 56)
Inside the method, circle initially refers to myCircle. The method changes the x and y coordinates of the object that circle references (i.e., myCircle) by 23 and 56, respectively. These changes will persist when the method returns. Then circle is assigned a reference to a new Circle object with x = y = 0. This reassignment has no permanence, however, because the reference was passed in by value and cannot change. Within the method, the object pointed to by circle has changed, but, when the method returns, myCircle still references the same Circle object as before the method was called.
I have a code in which I am reading input from System.in and Destination is some where else
Here is my code
File file=new File("D:/output.txt"); OutputStream os=new java.io.FileOutputStream(file); Scanner scanner=new Scanner(System.in); System.out.println("Enter Data to write on File"); String text=scanner.nextLine(); int c=Integer.parseInt(text); int a; while((a=c.read())!=-1) os.write(a); System.out.println("File Written is Successful");
In the line while((a=c.read())!=-1)
a compile time error is shown "cannot invoke read on primitive data type int"
I have to use a long primitive type for the input of a credit card number and ID the credit card by using the first number of the input; however, the only way I know for that is to use charAt, which is used for a String. Is there a way to convert long to String, or am I missing a better solution? (There's no code because I'm still doing the pseudocode).
I am currently working on modules of a java program but am having issues with this module . it gives this error code"syntax error on token '?', invalid primitive type".
I have set up a project in Eclipse 3.1 and am using java 5.0 compiler.
Here's my folder structure in Eclipse
Java Code:
DFSRemoteClientTestClient.java mh_sh_highlight_all('java'); DFS is the project in Eclipse
And this is how it looks my java class
Java Code:
package RemoteClient; import java.util.*; // other imports public class TestClient { public static void main(String [] args) throws ServiceInvocationException { // business logic here .... } } mh_sh_highlight_all('java');
So, basically, my java class is just a simple class with a main function.
Now when I build my project, using Project->Clean...
Then I get this as an error at the very first line where i specify the package
This is the error:
Java Code: The type Class is not generic; it cannot be parameterized with arguments <T> mh_sh_highlight_all('java');
I have an int array that has information read from a file. Now i want to display this int on a jtable but ofcourse i cant display primitive data types.. and also you cannot cast an int[] to an Object[], so I am stuck...
Trying to find a way to use primitive data types to overload sound()method. I can't seem to warp my head around using an int or a double to overload the method. And if I did, how do you call them in the main afterwards?
I get an error when I try to divide 500 miles by 25.5 gallons
Exception in thread "main" java.lang.NumberFormatException: For input string: "25.5" at java.lang.NumberFormatException.forInputString(Num berFormatException.java:65) at java.lang.Integer.parseInt(Integer.java:580) at java.lang.Integer.parseInt(Integer.java:615) at Mileage.main(Mileage.java:42) Java Result: 1
So I want to know how in Java you can pass a unkown type into a method (type can be an int, double, or a user defined object) and return that unkown type.
example of what I want: Java Code: public (unknowntype)[] method2 ((unknowntype)[]) //Process Data //unknowntype.process(); return (unknowntype); } mh_sh_highlight_all('java');
I know in C you can use void pointers and in c++ we have templates but I do not know how java handles this. Also I want to know if it is possible to call a method in the unknowntype.
import java.awt.*; import java.awt.event.*; import java.sql.*; public class ChickenListener implements ActionListener { int loopctrl; static Connection cn; static Statement st; static ResultSet rs; static PreparedStatement ps;
[Code]...
the second code
import java.awt.*; import java.awt.event.*; import java.sql.*; public class QuantityCounterListener implements ActionListener { String tempStrng; int tempInt; int x = 0;
[Code]...
what my problem is i need to transfer what does "tempString" from code 1 holds to code 2 in the //x part in the prepared statement.
I have created a DefaultTableModel tablel as a Global variable. The table is then created and attached to a Grid bag layout. Then I want to call the table again in another method to add rows of data into it. Hopefully that makes sense.
So the addrow for the table is located in the final method private class CalcButtonListener implements ActionListener
When I debug the code, deftablemodel variable is carrying NULL data.
Also to make things even more complicated, The actual headers for the table aren't showing up,... not entirely sure why though.
While practicing java i have came across boolean data type. i have executed below program but i am not sure how i got output of the program like below:
10 > 9 is true
Here is my program:
class BoolTest3 { public static void main(String args[]) { System.out.println("10 > 9 is "+(10>9)); } }
My question is: how this program will come to know that 10>9 true or false.. how bolean data type used in this program.
I was struggling to use BufferedReader to extract some data and then perform some calculations and then have the results as outputs.
I haven't quite solved that issue but in order to progress, I hard coded some values into my application and proceeded with the actual calculation loops etc.
Currently, the value out put from one of my calculations is given as:
1.1704926E7
How can I make the console show it in a natural way. I've performed the calculation manually and it should be 11704926.5 I don't want to lose that .5!
I am trying to use double data type in a for loop for precise operations and just to see if there could be any problem doing that I tested a small code :
public class doubleLimit { public static void main(String[] args){ for(double i=-0.1;i<=0;i+=0.01) System.out.println(i); }}
The output I was expecting is : -0.1 -0.09 -0.08 -0.07 -0.06 -0.05 -0.04 -0.03 -0.02 -0.01 0.00
But the output of the code is : -0.1 -0.09000000000000001 -0.08000000000000002 -0.07000000000000002 -0.06000000000000002 -0.05000000000000002 -0.040000000000000015 -0.030000000000000013 -0.02000000000000001 -0.01000000000000001 -1.0408340855860843E-17
Why is the code not working the way I expected, I think it has something to do with any property of double but I am not sure.
Is this the proper way to add to a generic list? My code works just fine, but I got this feeling that there might be some kind of flaw in it or something. Is this pretty much the basic way to add any type of data to a generic list?
import java.util.LinkedList; public class ListOfGeneric<E> { private LinkedList<E> myList;
public class InputFileData { /** * @param inputFile a file giving the data for an electronic * equipment supplier’s product range * @return an array of product details * @throws IOException */ public static Product [] readProductDataFile(File inputFile) throws IOException{ // YOUR CODE HERE }
This code is meant to be used to read a text file and store the data in an array of type Product[]. I know how to read in a text file and have it sort it into an array, but I've never seen code laid out in this fashion before (specifically "public static Product[]", and I'm unsure how to work with "(File inputfile)". I've looked all over the place but can't find any examples of anything like this.
Also, the code given cannot be changed, as it's that code I have to work with.
I still don't understand how to use it as a whole. For example, do I read the file in the main and have this method read that in and output to the Product class? Do I read the file in this method? I can't work out how to make this work when I have to use this method.
In my project i am facing an problem, The My SQL Data base will accept the date format of yyyy/mm/dd only as "Date" data type but in my program i wants to use dd/mm/yyyy format. (i have this same format now) that's why I am unable to insert / retrieve it..
