Java Tutorials

Concurrent Collections in Java

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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

Readers and Writers in Java

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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

Preferences in Java

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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

Command Line Argument Processing in Java

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A Java application can accept any number of command line argument. This allows the user to specify configuration information when the application is launched. When an application is launched, the runtime system passes the command line arguments to the application’s main method via an array of String s. Related Article: The Java Command – ‘java’ and ‘javaw’ Parameter Details … Read more

Java Commands & Options

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The java commands supports a wide range of options: All options start with a single hyphen or minus-sign (-): the GNU/Linux convention of using — for “long” options is not supported. Options must appear before the or the -jar argument to be recognized. Any arguments after them will be treated as arguments to be passed … Read more

Collect Elements of a Stream into a Collection in Java

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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

Finding Statistics about Numerical Streams in Java

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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

Using Streams and Method References to Write Self-Documenting Processes in Java

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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

Streams in Java

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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

Console I/O in Java

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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

Reference Types in Java

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Reference datatypes in java are those which contains reference/address of dynamically created objects. These are not predefined like primitive data types. Different Reference Types java.lang.ref package provides reference-object classes, which support a limited degree of interaction with the garbage collector. Java has four main different reference types. They are: Strong Reference Weak Reference Soft Reference Phantom … Read more

Local Inner Classe in Java

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Local Inner Classes are the inner classes that are defined inside a block. Generally, this block is a method body. … These classes have access to the fields of the class enclosing it. Local inner classes are must be instantiated in the block they are defined in. Basic Object Construction and Use in Java Objects come Basic Object Construction and Use in Java in … Read more

Generics in Java

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Generics are a facility of generic programming that extend Java’s type system to allow a type or method to operate on objects of various types while providing compile-time type safety. In particular, the Java collections framework supports generics to specify the type of objects stored in a collection instance. Related Article: Visibility (controlling access to … Read more