“Cannot be resolved to a type” when attempting to use Scanner
when i run following code it shows error that scanner cannot be resolved to type. i checked that jre is installed and version is 1.7 what else do i need to check ? please help.
java
Get Mouse Position
MouseInfo.getPointerInfo().getLocation() might be helpful. It returns a Point object corresponding to current mouse position.
Exception in thread “AWT-EventQueue-0”?
You don’t ever initialize the JTextArea member field called textArea. You are shadowing the member field in your declaration. Try this: instead of
Popup Message boxes
javax.swing.JOptionPane Here is the code to a method I call whenever I want an information box to pop up, it hogs the screen until it is accepted: The first JOptionPane parameter (null in this example) is used to align the dialog. null causes it to center itself on the screen, however any java.awt.Component can be … Read more
Javac “cannot find symbol”
First, To compile the java source file using javac you need to specify the files to compile explicitly. Example: you need not provide the path if the source file is in the current working directory. Second, whenever java encounters import abc.xyz.ClassName; it tries to resolve abc/xyz/ClassName with respect to the classpath or current working directory. … Read more
What’s wrong with overridable method calls in constructors?
On invoking overridable method from constructors Simply put, this is wrong because it unnecessarily opens up possibilities to MANY bugs. When the @Override is invoked, the state of the object may be inconsistent and/or incomplete. A quote from Effective Java 2nd Edition, Item 17: Design and document for inheritance, or else prohibit it: There are … Read more
What does it mean: The serializable class does not declare a static final serialVersionUID field? [duplicate]
From the javadoc: The serialization runtime associates with each serializable class a version number, called a serialVersionUID, which is used during deserialization to verify that the sender and receiver of a serialized object have loaded classes for that object that are compatible with respect to serialization. If the receiver has loaded a class for the … Read more
Java Exception in thread “AWT-EventQueue-0” java.lang.NullPointerException
OK what I am trying to do here is create a game where the object/ball is controlled by clicking on the object with the mouse, pulling back the mouse (the distance the mouse is pulled back will determine the velocity of the object) and on releasing the button the object will move (it’s angle of … Read more
java.lang.ArrayIndexOutOfBoundsException: 0
Problem This ArrayIndexOutOfBoundsException: 0 means that the index 0 is not a valid index for your array args[], which in turn means that your array is empty. In this particular case of a main() method, it means that no argument was passed on to your program on the command line. Possible solutions If you’re running … Read more
unexpected type error
The problem is here: The left-hand-side is a value. Not a variable. That’s why you can’t to a += to it. Although it defeats the purpose of learning how do it the hard way, you can do it like this: