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'm making a Hangman program for Java, here's my code:
import java.util.Scanner; public class Hangman { /** * @param args the command line arguments */ public static void main(String[] args) { String answerWord = WordList.getWord();
[Code] .....
The Compiler gives me this only error:
Hangman.java:39: error: unexpected type displayWord.charAt(i)=userInput.charAt(0); ^ required: variable found: value
I understand that charAt returns i as a value and not a variable. What do I use to return a variable as I intended?
public class Class1 extends AbstractClass { //stuff } public class Class2 extends AbstractClass { //stuff }
within another class I have a private variable with the type of the Abstract class, and within one of the methods I assign an object to the the variable like this:
public class Test { private AbstractClass temp; public testMethod(){ Class1 anObject = new Class1(); temp = anObject; } }
I don't understand how i'm supposed to define a variable when the user has to type it into the program so it can be converted. This program i'm working on is supposed to convert from meters to feet (meter = feet * 0.305) but the user has to type in the meters they want converted. how do i solve the problem that keeps coming up that says "variable meter symbol cant be found" ? I keep trying different lines to no avail
public class Lab2 { public static void main(String[] args) { double feet = meter * 0.305; double meter = feet/0.305; System.out.println("Enter in feet for conversion to meters"); meter = meter * 0.305;
I have created an enumerated data type that represents months. In my program I have asked the user for the month. I hold the month entered by user into a string variable. From that string variable I'm trying to display the month using my enumerated data type. I know I can use if statements, but is there another simple way to do it?
import java.util.Scanner; public class demo { //Enum class called month that has constants in it representing months enum month{january,february,march,april,may,june, july,august,september, october,november, december};
I have a JavaFX application with multiple scenes. In the application one scene plays the "master" role and the others are loaded according to actions . The issue i have is that i need to redirect all the PrintStream activity to a specific TextArea on the "master" scene, and by "all" i am meaning every PrintStream activity on every scene should be redirected to this specific TextArea . The code i am using on the "master" is :
Node node =primaryStage.getScene().lookup("#ShowInfo"); TextArea ta =(TextArea)node; FXConsole console = FXConsole.getInstance(ta); PrintStream ps = new PrintStream(console, true); System.setOut(ps); System.setErr(ps); System.out.println("Test");
I am using the Singleton pattern for the rest of the scenes :
I want to write formatted output on a notepad file using ObjectOutputStream but I am not getting it in human readable formatted form
Here is my person class
public class Person implements Serializable { private String firstName; private String lastName; private int age; public String getFirstName() { return firstName;
[code]....
I want to know how to use printStream.print() like method to write formatted output.
I know that System is a final class and it cannot be instantiated, out is a static final variable of type PrintStream in System class and println is a method in PrintStream class.Still I don't understand why we use System.out to call println() method.To my knowledge a method can be called using an object reference, in case of static behaviors we use classname. Then why here we are using System.out.println? Can't we just create an object of PrintStream class and call the println() method as PrintStream class can be instantiated.Are there any ways of calling a method apart from those I know(I have mentioned above what I know)?
My problem: Every time a new account is created all previous accounts will be deleted because I use: u.println(""); and p.println(""); How can I fix this problem?
I have a JavaFX application with multiple scenes. In this applications one scene plays the role of "master" role and the others are loaded according to actions on the "master" scene(buttons,menu items)
The issue is that i need to redirect all the PrintStream activity to a specific TextArea on the "master" scene...
So everything that normally goes to the console to get redirected to that specific TextArea and this should be global,on every scene that is outputting something it should displayed on the specific TextArea on the "master" scene
The code i am using right now on the "master" scene is :
Node node =primaryStage.getScene().lookup("#ShowInfo"); TextArea ta =(TextArea)node; FXConsole console = FXConsole.getInstance(ta); PrintStream ps = new PrintStream(console, true); System.setOut(ps); System.setErr(ps); System.out.println("Test");
For the rest of the scenes i am using the Singleton Pattern to keep the pointing to the Specific TextArea
I don't understand why the object reference variable 'a' cannot be recast from a thisA object reference to a thisB object reference.Is it the case that once a reference variable is linked to a particular object type then it cannot switch object types later on.I am facing the Java Associate Developer exam soon and I am just clearing up some issues in my head around object reference variable assignment,
class thisA {} class thisB extends thisA { String testString = "test";} public class CastQuestion2 { public static void main(String[] args) { thisA a = new thisA(); thisB b = new thisB();
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?
The term "Local variable" is related to scope. That is a local variable is one which is defined in a certain block of code, and its scope is confined inside that block of code.And a "Member variable" is simple an instance variable.
I read in a discussion forum that when local variables are declared (example code below), their name reservation takes place in memory but they are not automatically initialized to anything. On the other hand, when member variables are declared, they are automatically initialized to null by default.
Java Code: public void myFunction () { int [] myInt; // A local, member variable (because "static" keyword is not there) declared } mh_sh_highlight_all('java');
So it seems that they are comparing local variables and member variables. While I think a member variable can also be be local in a block of code, isn't it?
when we create another variable and set it equal to the first : Car c2 = c1;
we're pointing c2 at the same car object that c1 points to (as opposed to pointing c2 at c1, which in turn points at the car). So if we have code like,
Car c1 = new Car(); Car[] cA = {c1, c1, c1, c1};
are we doing the same? Are we creating four *new* reference variables, each of which points at the same car (again as opposed to pointing them at c1 itself)? I think so, but want to make sure I'm understanding this correctly.
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);
