How-to articles, tricks, and solutions about JAVA-8

In Java 8, the :: (double colon) operator is used to refer to a method or a constructor.

To break or return from a Java 8 Stream.forEach() operation, you can use the break or return statements as you would normally do in a loop.

If you get the error "class has been compiled by a more recent version of the Java Environment", it means that you are trying to run a class file that was compiled with a newer version of Java than the one you have installed.

To convert a java.time.LocalDate into a java.util.Date type in Java, you can use the atStartOfDay() method of the LocalDate class to get a LocalDateTime object and then use the toInstant() method to convert it to an Instant object.

To convert a java.util.Date object to a java.time.LocalDate object, you can use the java.time.Instant class to represent the date as an instant in time, and then use the java.time.LocalDateTime class to convert the instant to a date and time in the local

This error message usually indicates that you are trying to compile your Java code with a version of the javac compiler that is not compatible with the version of the Java language that your code is written in.

To find the first element in a list that matches a certain condition, you can use the stream() method to create a stream from the list, and then use the filter() method to specify the condition that the element should satisfy. Finally, you can use the fin

The ifPresent() and ifPresentOrElse() methods of the Optional class in Java 8 provide a functional style way to perform different actions depending on whether the Optional object is empty or contains a value.

In Java 8 and later, you can use the java.time.LocalDateTime class to represent a date and time without a time zone. To parse a date and time string into a LocalDateTime object, you can use the java.time.format.DateTimeFormatter class.

You can use the flatMap method from the Stream API to turn a List<List<T>> (a list of lists) into a List<T> in Java 8. Here's an example of how you can do this:

To convert a Java 8 Stream to an array, you can use the toArray() method of the Stream interface.

To get the milliseconds from a LocalDateTime object in Java 8, you can use the toInstant method and the toEpochMilli method.

To install Java 8 on macOS, follow these steps:

You can use the reduce() operation in the Java Streams API to sum the elements of a list of integers.

To use a Java 8 lambda to sort a stream in reverse order, you can use the sorted() method of the Stream interface and pass a lambda function that compares the elements in reverse order.

To get a list of distinct elements by a property in Java 8, you can use the distinct() method of the Stream interface and the map() method to extract the property from each element.

In Java 8, the Iterable.forEach() method is a default method that allows you to iterate over the elements of an Iterable (such as a List or Set) and perform a specific action on each element.

In Java 8, you can use a lambda expression to create a functional interface that throws an exception.

To convert a List<V> into a Map<K, V> in Java 8, you can use the toMap() method of the Collectors class from the java.util.stream package.

To find the difference between two LocalDateTime objects in multiple units, you can use the Duration class.

You can use the map and collect methods of the Stream class to achieve this.

In Java 8, the map() and flatMap() methods are part of the Stream API, and are used to transform the elements of a stream.