Running JAR file on Windows

Easiest route is probably upgrading or re-installing the Java Runtime Environment (JRE). Or this: Open the Windows Explorer, from the Tools select ‘Folder Options…’ Click the File Types tab, scroll down and select JAR File type. Press the Advanced button. In the Edit File Type dialog box, select open in Actions box and click Edit… … Read more

What is the best way to implement constants in Java?

That is perfectly acceptable, probably even the standard. where TYPE is the type, NAME is the name in all caps with underscores for spaces, and VALUE is the constant value; I highly recommend NOT putting your constants in their own classes or interfaces. As a side note: Variables that are declared final and are mutable … Read more

Java string to date conversion

That’s the hard way, and those java.util.Date setter methods have been deprecated since Java 1.1 (1997). Moreover, the whole java.util.Date class was de-facto deprecated (discommended) since introduction of java.time API in Java 8 (2014). Simply format the date using DateTimeFormatter with a pattern matching the input string (the tutorial is available here). In your specific case of “January 2, 2010” as the input … Read more

and in Java – why it works this way?

The way I look at it is this – the placeholder T stands in for a definite type and in places where we need to know the actual type we need to be able to work it out. In contrast the wildcard ? means any type and I will never need to know what that type is. You can … Read more

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