Java I/O (Input and Output) is used to process the input and produce the output. Java uses the concept of stream to make I/O operation fast. The java.io package contains all the classes required for input and output operations. Handling files is also done in java by Java I/O API. Migrating from java.io.File to Java … Read more
Optional is a container object which may or may not contain a non-null value. If a value is present, isPresent() will return true and get() will return the value. Additional methods that depend on the presence of the contained value are provided, such as orElse(), which returns a default value if value not present, and … Read more
Java provides a mechanism, called object serialization where an object can be represented as a sequence of bytes that includes the object’s data as well as information about the object’s type and the types of data stored in theobject. After a serialized object has been written into a file, it can be read from the … Read more
Multimap in Guava, Apache and Eclipse Collections This multimap allows duplicate key-value pairs. JDK analogs are HashMap, HashMap and so on. Examples using Multimap Task: Parse “Hello World! Hello All! Hi World!” string to separate words and print all indexes of every word using MultiMap (for example, Hello=[0, 2], World!=[1, 5] and so on) MultiValueMap … Read more
Documentation for java code is often generated using Javadoc. Javadoc was created by Sun Microsystems for the purpose of generating API documentation in HTML format from Java source code. Using the HTML format gives the convenience of being able to hyperlink related documents together. Building Javadocs From the Command Line Many IDEs provide support for … Read more
A regular expression is a special sequence of characters that helps in matching or finding other strings or sets of strings, using a specialized syntax held in a pattern. Java has support for regular expression usage through the java.util.regex package. This topic is to introduce and help developers understand more with examples on howRegular Expressions … Read more
Java Interfaces Tutorial – An interface is a reference type, similar to a class, which can be declared by using the interface keyword. Interfaces can contain only constants, method signatures, default methods, static methods, and nested types. Method bodies exist only for default methods and static methods. Like abstract classes, Interfaces cannot be instantiated—they can … Read more
In this Java Scanner Tutorial, we will learn about Java Scanner and its methods with the help of examples. Parameter Details Source Source could be either one of String, File or any kind of InputStream General Pattern that does most commonly asked about tasks The following is how to properly use the java.util.Scanner class to … Read more
Creating paths The Path class is used to programmatically represent a path in the file system (and can therefore point to files as well as directories, even to non-existent ones) A path can be obtained using the helper class Paths: Path p1 = Paths.get(“/var/www”);Path p2 = Paths.get(URI.create(“file:///home/testuser/File.txt”));Path p3 = Paths.get(“C:\Users\DentAr\Documents\HHGTDG.odt”);Path p4 = Paths.get(“/home”, “arthur”, “files”, … Read more
In this tutorial, we will learn about Java BufferedWriter and its methods with the help of code examples. Write a line of text to File This code writes the string to a file. It is important to close the writer, so this is done in a finally block. public void writeLineToFile(String str) throws IOException { … Read more
The switch statement is Java’s multi-way branch statement. It is used to take the place of long if-else if-else chains, and make them more readable. However, unlike if statements, one may not use inequalities; each valuemust be concretely defined. Switch statements There are three critical components to the switch statement: case: This is the value … Read more
Lambda expressions provide a clear and concise way of implementing a single-method interface using an expression. They allow you to reduce the amount of code you have to create and maintain. While similar toanonymous classes, they have no type information by themselves. Type inference needs to happen. Method references implement functional interfaces using existing methods … Read more
Object References as method parameters This topic explains the concept of an object references; it is targeted at people who are new to programming in Java. You should already be familiar with some terms and meanings: class definition, main method, object instance, and the calling of methods “on” an object, and passing parameters to methods. … Read more
All Java exceptions are instances of classes in the Exception class hierarchy. This can be represented as follows: java.lang.Throwable – This is the base class for all exception classes. Its methods and constructors implement a range of functionality common to all exceptions. java.lang.Exception – This is the superclass of all normal exceptions. various standard and … Read more
The Exception Handling in Java is one of the powerful mechanism to handle the runtime errors so that normal flow of the application can be maintained. Objects of type Throwable and its subtypes can be sent up the stack with the throw keyword and caught with try…catch statements. Catching an exception with try-catch An exception can be caught and … Read more
The properties object contains key and value pair both as a string. The java.util.Properties class is the subclass of Hashtable. It can be used to get property value based on the property key. The Properties class provides methods to get data from properties file and store data into properties file. Moreover, it can be used … Read more
The static keyword in Java is used for memory management mainly. We can apply static keyword with variables, methods, blocks and nested classes. The static keyword belongs to the class than an instance of the class. Reference to non-static member from static context Static variables and methods are not part of an instance, There will always be a single copy of … Read more
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
Super keyword use with examples super keyword performs important role in three places Constructor Level Method Level Variable Level Constructor Level super keyword is used to call parent class constructor. This constructor can be default constructor or parameterized constructor. Default constructor : super(); Parameterized constructor : super(int no, double amount, String name); class Parentclass { … 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.