Alright, let’s elaborate with some simplified explanation about the Scanner class. It is a standard Oracle class which you can use by calling the import java.util.Scanner. So let’s make a basic example of the class: Now when you call Scanner input = new Scanner(System.in); you make a new object of the Scanner class (so you make a new “Scanner”) and you store … Read more
Everything in a Java program not explicitly set to something by the programmer, is initialized to a zero value. For references (anything that holds an object) that is null. For int/short/byte/long that is a 0. For float/double that is a 0.0 For booleans that is a false. For char that is the null character ‘\u0000’ (whose decimal equivalent is 0). When … Read more
The HTTP 502 “Bad Gateway” response is generated when Apache web server does not receive a valid HTTP response from the upstream server, which in this case is your Tomcat web application. Some reasons why this might happen: Tomcat may have crashed The web application did not respond in time and the request from Apache … Read more
In terms of Java, both the class HashMap and the class Dictionary are implementations of the “Map” abstract data type. Abstract data types are not specific to any one programming language, and the Map ADT can also be known as a Hash, or a Dictionary, or an Associative Array (others at http://en.wikipedia.org/wiki/Associative_array). (Notice we’re making a distinction between the Dictionary class and the Dictionary … Read more
It’s a static initializer. It’s executed when the class is loaded (or initialized, to be precise, but you usually don’t notice the difference). It can be thought of as a “class constructor”. Note that there are also instance initializers, which look the same, except that they don’t have the static keyword. Those are run in addition to the code in the constructor … Read more
java is part of the JRE, not the JDK. You need to add the JDK bin to the system PATH, in “Control Panel” | System | Advanced | “Environment Variables”
Try the following Rebuilding the project Cleaning the project Syncing with Gradle Files Closing the Project, closing AS and relaunching / reopening File > Invalidate Caches / Restart Double checking all support libraries are up to date in the SDK manager Exit Android Studio Back up your project Delete all the .iml files and the … Read more
Launch4j works on both Windows and Linux/Mac. But if you’re running Linux/Mac, there is a way to embed your jar into a shell script that performs the autolaunch for you, so you have only one runnable file: exestub.sh: Then you create your runnable file from your jar: It works the same way launch4j works: because a … Read more
You cannot overload operators in Java. The < operator only applies to primitive (or numeric) types, not reference types. Since T is a type variable that represents a reference type, you cannot use < on variables of type T. You have to use check the value returned and decide to do what you wish with … Read more
If you want that for display purposes, use java.text.DecimalFormat: If you need it for calculations, use java.lang.Math: