java - Read For Learn

Error: A JNI error has occurred, please check your installation and try again – during running Java program from Ubuntu terminal

The error says it all: Exception in thread “main” java.lang.UnsupportedClassVersionError: Test has been compiled by a more recent version of the Java Runtime (class file version 55.0)… You’ve compiled for Java 11 … but you’re running an older JRE (Java 8). SUGGESTIONS: recompile with -source and -target to target an earlier version of Java in your .class file, or … Read more

What does the following Oracle error mean: invalid column index

If that’s a SQLException thrown by Java, it’s most likely because you are trying to get or set a value from a ResultSet, but the index you are using isn’t within the range. For example, you might be trying to get the column at index 3 from the result set, but you only have two … Read more

Convert java.util.Date to String

Convert a Date to a String using DateFormat#format method: From http://www.kodejava.org/examples/86.html

Reading in from System.in – Java

You can use System.in to read from the standard input. It works just like entering it from a keyboard. The OS handles going from file to standard input.

How do I resolve the “java.net.BindException: Address already in use: JVM_Bind” error?

Yes you have another process bound to the same port. TCPView (Windows only) from Windows Sysinternals is my favorite app whenever I have a JVM_BIND error. It shows which processes are listening on which port. It also provides a convenient context menu to either kill the process or close the connection that is getting in the way.

Why is there no Constant feature in Java?

Every time I go from heavy C++ coding to Java, it takes me a little while to adapt to the lack of const-correctness in Java. This usage of const in C++ is much different than just declaring constant variables, if you didn’t know. Essentially, it ensures that an object is immutable when accessed through a special kind of pointer … Read more

Best Java obfuscator?

First, you really need to keep in mind that it’s never impossible to reverse-engineer something. Everything is hackable. A smart developer using a smart IDE can already get far enough. Well, you can find here a list. ProGuard is pretty good. I’ve used it myself, but only to “minify” Java code.

Recompile with -Xlint:unchecked for detail error in java

When you compile the code use this: Then you will see: So bottom line, the problem is due to the creation of the generic type array. To solve this read this link: https://stackoverflow.com/a/530289/588532

java.text.ParseException: Unparseable date

Your pattern does not correspond to the input string at all… It is not surprising that it does not work. This would probably work better: Then to print with your required format you need a second SimpleDateFormat: Notes: you should include the locale as if your locale is not English, the day name might not … Read more

How to create PPTP connection with Java?

I need to check what accounts from my huge list are still valid on VPN-server, but I haven’t found any information on how to do it with Java language. How do I connect to PPTP-server using Java? I created a socket with the server ip and PPTP-port, just like this, according to PPTP working over … Read more

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