Is Type Irrelevant As Long As Value Is Within Boundaries Of Type Of Switch Expression
Apr 30, 2014
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?
The objective of the code is to add new records based on existing records with a partial change to the key. I'm getting "type of the expression must be an array type but it resolved to DstidArray" on dsTidRecTbl[i]
String stMajor = request.getParameter("stMajorVersion"); String stMinor = request.getParameter("stMinorVersion"); String stPatch = request.getParameter("stPatchVersion"); StringBuffer stKeySB = new StringBuffer(stMajor+stMinor+stPatch); String stKey = new String(stKeySB.toString()); DstidArray dsTidRecTbl = new DstidArray(stKey); request.setAttribute("dsTidRecTbl", dsTidRecTbl);
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 tried to create file and write the output of my program in it in java when i use WriteLong then the file does not contain long value, how I create this file my program is to print prime numbers between 500000 to 10000000
public class primenumber { public static void main(String[] args) { long start = 5000000; long end = 10000000; System.out.println("List of prime numbers between " + start + " and " + end); for (long i = start; i <= end; i++) { if (isPrime(i)) { System.out.println(i);
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?
Take a Java (Oracle SE 7 JVM) long, primitive or it's wrapper class... assign a variable with the value slightly less than 2^63-1 (the maximum value... i.e. infinity? for a long); keep adding 1. What happens? You quite quickly get - minimum long, or minus infinity (?).Infinity is my perspective from a Mathematics degree.
I don't really know what this means and it is sending an error when I try to run my program I am trying to set the x and y value (Int x and int y) to setVisible false at a specific time in my game but it keeps sending the error that int is not a reference type.
I am trying to understand Life time of a variable by writing a below program. But unable to compile it as it is throwing some error. Code snippet and error as follows,
// Understanding Lifetime of a variable. class LifeTime { public static void main(String args[]) { int x; for(x = 0; x <3 ; x++) { int y = -1; // y is initialized each time block is entered
[Code] .....
Please refer to the print screen attached 'LifeTime.jpeg' to this thread to know more about error.
I want to implement a kind of "container" in which to store objects (instances) of different types. Then with an iterator I'd call common methods. This is what I have in mind:
Where translate(x, y, z) is a method common for objects in Positionables which objects are of different types (Sphere, Box etc.).
Now I was thinking Positionables could be a List<Positionable> and Positionable is an abstract class and Sphere and Box extends from it. But I don't know how to propagate the call of translate() to the subclasses.
What are the best approaches for this matter? It would be perfect if I could make it so I could somehow use the "with" construction like in the example above.
For some reason when I try to run the program it gives me an "editor does not contain a main type" launch error.
/* * A program that plays and scores a round of the game Poker Dice. In this game, five dice are rolled. The player is allowed to select a number of those five dice to re-roll. The dice are re-rolled and then scored as if they were a poker hand. The following hands MUST be scored in this assignment: * * High card * * One Pair * * Two Pair * * Three of a Kind * * Full House * * Four of a Kind * * Five of a Kind * For extra credit, you may also implement: * * Straight */
import java.util.Scanner; public class Project10 { public static void main(String[] args) { Scanner inScanner = new Scanner(System.in); int[] dice = new int[5]; resetDice(dice); System.out.print("Your current dice: + dice");
If I don't append the L, is the msb (most significant bit) somehow still carried over to the resulting long variable and in the latter case, where I append an L, it is not and instead the value is filled up with 32 leading zeros (4 Byte difference between int and long)?
This means that x is a reference to objects of type, "myType" and no memory has been set aside for an instance of this object. I think it's true that x also has the starting memory address of this object.
What I feel uncertain about is if x is telling the JVM(?) where it can find the starting address of this object, why do we care about the type that x is?
i.e., if we assign x to an object totally unrelated to this type then the compiler would complain - correct? If so, how come, since all x is doing is telling the JVM(?) where to find your object (via the address it contains).
I suppose all, hy a reference has a type associated with it if all the reference does is point you to the object?
I'm trying to run a simple code which is to just print out "Hello World", but whenever I run it, a message appears that reads: "Select a way to run Project_1(Which is the Java Project)"
The selections for it are: Java Applet and Java Application.Whenever I click Java Applet it reads: Selection does not contain an applet.When I click Java Application: Selection does not contain a main type.Here is the code which I believe is correct:
package packag_1; public class Num_1 { public static void main(String args){ System.out.println("Hello World"); } }
I recently switched some of code around to restructure how some things were working but now when I run the program I am getting a NullPointerException in multiple areas. I suspect it may have something to do with a constructor. I am very new to "object" - ish based programming.
I figured I should give a little background on the program, this program is reading from a text file of names and decade numbers(for each name) and storing each line into an object array. From there, there are menus and based on the users decision they can type a name and get a histogram, compare names with histograms, ect. Below this main method, I have provided the area where I have gotten the null pointer exception.
Here is the main method for the Client "nameApp"
Also excuse the formatting and curly braces for now!
And here is the method in the same Client that is getting the null pointer exception:
The pointer exception is on line 6 which is:
if (nameInput.equalsIgnoreCase(list[i].getName())){ private static int checkListArray(String nameInput, Name[] list){ int nameLocation = -1; int listLength = list.length;
String contentType = fi.getContentType(); gives text/plain when my file is.txt file and gives image/jpeg when my file is .jpeg file but when my file is .jar or .docx it will return application/octet-stream and application/vnd.openxmlformats-officedocument.wordprocessingml.document respictively so what to do to get exact mime type.
