Coding Compiler

Creating Calendar objects Calendar objects can be created by using getInstance() or by using the constructor GregorianCalendar. It’s important to notice that months in Calendar are zero based, which means that JANUARY is represented by an int value 0. In order to provide a better code, always use Calendar constants, such as Calendar.JANUARY to avoid … Read more

Java offers a wide variety of Collections. Choosing which Collection to use can be tricky. See the Examples section for an easy-to-follow flowchart to choose the right Collection for the job. Java Collections Flowchart Use the following flowchart to choose the right Collection for the job.

A concurrent collection is a [collection][1] which permits access by more than one thread at the same time. Different threads can typically iterate through the contents of the collection and add or remove elements. The collection is responsible for ensuring that the collection doesn’t become corrupt. Thread-safe Collections By default, the various Collection types are … Read more

Method w/ Parameter Description List.of(E e) A generic type that can be a class or interface. Set.of(E e) A generic type that can be a class or interface. Map.of(K k, V v) A key-value pair of generic types that can each be a class or interface. Map.of(Map.Entry<? extends V> entry) A Map.Entry instance where its … Read more

Readers and Writers and their respective subclasses provide simple I/O for text / character-based data. BufferedReader Introduction The BufferedReader class is a wrapper for other Reader classes that serves two main purposes: A BufferedReader provides buffering for the wrapped Reader. This allows an application to read charactersmone at a time without undue I/O overheads. A … Read more

Using preferences Preferences can be used to store user settings that reflect a user’s personal application settings, e.g. their editor font, whether they prefer the application to be started in full-screen mode, whether they checked a “don’t show this again” checkbox and things like that. public class ExitConfirmer { private static boolean confirmExit() { Preferences … Read more

Closing Streams Most streams must be closed when you are done with them, otherwise you could introduce a memory leak or leave a file open. It is important that streams are closed even if an exception is thrown. Version ≥ Java SE 7 try(FileWriter fw = new FileWriter(“outfilename”); BufferedWriter bw = new BufferedWriter(fw); PrintWriter out … Read more

Elements from a Stream can be easily collected into a container by using the Stream.collect operation: Collect with toList() and toSet() Elements from a Stream can be easily collected into a container by using theStream.collect operation: System.out.println(Arrays .asList(“apple”, “banana”, “pear”, “kiwi”, “orange”) .stream() .filter(s -> s.contains(“a”)) .collect(Collectors.toList()) ); // prints: [apple, banana, pear, orange] Other … Read more

Java 8 provides classes called IntSummaryStatistics, DoubleSummaryStatistics and LongSummaryStatistics which give a state object for collecting statistics such as count, min, max, sum, and average. Version ≥ Java SE 8 List naturalNumbers = Arrays.asList(1, 2, 3, 4, 5, 6, 7, 8, 9, 10); IntSummaryStatistics stats = naturalNumbers.stream() .mapToInt((x) -> x) .summaryStatistics(); System.out.println(stats); Which will result … Read more

Method references make excellent self-documenting code, and using method references with Streams makes complicated processes simple to read and understand. Consider the following code: public interface Ordered { default int getOrder(){ return 0; } } public interface Valued { boolean hasPropertyTwo(); V getValue(); } public interface Thing { boolean hasPropertyOne(); Valued getValuedProperty(); } public List … Read more

A Streams represents a sequence of elements and supports different kind of operations to perform computations upon those elements. With Java 8, Collection interface has two methods to generate a Stream: stream() andparallelStream(). Stream operations are either intermediate or terminal. Intermediate operations return a Stream so multiple intermediate operations can be chained before the Stream … Read more

The Java Console class is be used to get input from console. It provides methods to read texts and passwords. If you read password using Console class, it will not be displayed to the user. The java.io.Console class is attached with system console internally. Reading user input from the console Using BufferedReader: System.out.println(“Please type your … Read more