List<String> list = ..; String[] array = list.toArray(new String[0]); For example: List<String> list = new ArrayList<String>(); //add some stuff list.add(“android”); list.add(“apple”); String[] stringArray = list.toArray(new String[0]); The toArray() method without passing any argument returns Object[]. So you have to pass an array as an argument, which will be filled with the data from the list, … Read more
Press Back when you get the notification and then Next. This time it will find the JDK.
Since JSR 305 (whose goal was to standardize @NonNull and @Nullable) has been dormant for several years, I’m afraid there is no good answer. All we can do is to find a pragmatic solution and mine is as follows: Syntax From a purely stylistic standpoint I would like to avoid any reference to IDE, framework … Read more
ServletContext When the servlet container (like Apache Tomcat) starts up, it will deploy and load all its web applications. When a web application is loaded, the servlet container creates the ServletContext once and keeps it in the server’s memory. The web app’s web.xml and all of included web-fragment.xml files is parsed, and each <servlet>, <filter> … Read more
Oracle has a poor record for making it easy to install and configure Java, but using Homebrew, the latest OpenJDK (Java 14) can be installed with: brew install –cask adoptopenjdk8 For the many use cases depending on an older version (commonly Java 8), the AdoptOpenJDK project makes it possible with an extra step. brew tap … Read more
Since Date implements Comparable, it has a compareTo method just like String does. So your custom Comparator could look like this: public class CustomComparator implements Comparator<MyObject> { @Override public int compare(MyObject o1, MyObject o2) { return o1.getStartDate().compareTo(o2.getStartDate()); } } The compare() method must return an int, so you couldn’t directly return a boolean like you … Read more
The org.json library is easy to use. Just remember (while casting or using methods like getJSONObject and getJSONArray) that in JSON notation [ … ] represents an array, so library will parse it to JSONArray { … } represents an object, so library will parse it to JSONObject Example code below: import org.json.*; String jsonString … Read more
First, it’s kind of weird, to see you run java -jar “app” and not java -jar app.jar Second, to make a jar executable… you need to jar a file called META-INF/MANIFEST.MF the file itself should have (at least) this one liner: Main-Class: com.mypackage.MyClass Where com.mypackage.MyClass is the class holding the public static void main(String[] args) … Read more
Iterator.remove() is safe, you can use it like this: List<String> list = new ArrayList<>(); // This is a clever way to create the iterator and call iterator.hasNext() like // you would do in a while-loop. It would be the same as doing: // Iterator<String> iterator = list.iterator(); // while (iterator.hasNext()) { for (Iterator<String> iterator = … Read more
Code : public class JavaApplication { public static void main(String[] args) { System.out.println(“Working Directory = ” + System.getProperty(“user.dir”)); } } This will print the absolute path of the current directory from where your application was initialized. Explanation: From the documentation: java.io package resolve relative pathnames using current user directory. The current directory is represented as … Read more