You need to somehow give class Alpha a reference to cBeta. There are three ways of doing this. 1) Give Alphas a Beta in the constructor. In class Alpha write: and call cAlpha = new Alpha(cBeta) from main() 2) give Alphas a mutator that gives them a beta. In class Alpha write: and call cAlpha … Read more
This is wrong: The problem is, what’s going to wake this thread up? That is to say, how do you guarantee that the other thread won’t call foo.notify() before the first thread calls foo.wait()? That’s important because the foo object will not remember that it was notified if the notify call happens first. If there’s … Read more
Firstly, I am considering my answer to show you another better way for connection with MySQL Database, it’s much easier and less nu-expected Exception(s).You need to do some steps: Download Connector/J and add it to your class path(if you are using an IDE there is add the .jar to the library, or there is many … Read more
So i’m a student in high school new to the Java language and i’m using this program called jgrasp, which we use to program java. I just got the program for home to try to finish off a lab I was working on and when I compile, this shows up: I just recently upgraded my … Read more
Every JPanel is a container, so either add it to a panel then add it to the container or directly use add(component) or use the getContentPane().add method. Both add the component to the container in Java 7 (I don’t know if version 6 has a problem with this or not).
On Windows, Java prevents starting the Installer twice by creating (two) lock files. If those files exist, Java Installer show the Message: “Another Java installation is in progress (…)”. If Java Installer crashes, or Windows crashes during Java Installation, the installer cannot delete the lock files when finalizing. Solution: Deleting the lock files, unlocks the … Read more
There are a couple of awkward things with your example class: it’s called People while it has a price and info (more something for objects, not people); when naming a class as a plural of something, it suggests it is an abstraction of more than one thing. Anyway, here’s a demo of how to use a Comparator<T>: EDIT And an … Read more
First of all, this is a compilation error. If you see the message it at runtime, you are probably running code that has compilation errors. Here are a couple of examples of the error: In both cases, the compiler error message will be error: ‘.class’ expected. What does the error message mean and what causes it? The … Read more
You can just copy the value of readln2 into a final variable: If you want to grab a new random line each time, you can either cache the lines of interest and select a random one in the event handler: Or you could just re-read the file in the event handler. The first technique is (much) faster but could … Read more
You can have an overflow when doing mathematic opetations between integers and chars, this can affect the expected result since that value is going to be assigned to a char… here you have but you should cast to char like: