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Articles by raja
Page 33 of 38
What is the use of the Tab key in JShell in Java 9?
JShell can also provide an auto-completion feature when we partially type the name of an existing class, variable, or method by pressing the Tab key. If an item can't determine from what we entered, then possible options are provided.Pressing the Tab key in JShell performs one of the following tasks:If no other name matches what we have typed, JShell enters the rest of the name for us.If there are multiple names that begin with the same letters, then JShell displays a list of those names to help what to type next, then type the next letter(s) and press tab key ...
Read MoreHow can we create an unmodifiable List in Java 9?
A list considered to be unmodifiable if the elements can't be added, removed, or replaced from a list once an unmodifiable instance of a list has created. The static factory method: List.of() provides a convenient way to create unmodifiable lists in Java 9.An instance of a list created by using the List.of() method has the following characteristics.The list returned by a factory method is conventionally immutable. It means that the elements can't be added, removed, or replaced from a list. Calling any mutator method on the List causes UnsupportedOperationException.If the contained elements of List are mutable, it may cause the ...
Read MoreImportance of iterate() method of Stream API in Java 9?
In Java 8, the iterate() method of Stream API takes the seed and the unary operator as arguments. As stream becomes infinite, it makes the developer add explicit termination conditions by using limit, findFirst, findAny and etc. In Java 9, the iterate() method of Stream API has added a new argument, a predicate that takes the condition to break the flow.Syntaxstatic Stream iterate(T seed, Predicate
Read MoreHow to add/insert additional property to JSON string using Gson in Java?
The com.google.gson.JSonElement class represents an element of Json. We can use the toJsonTree() method of Gson class to serialize an object's representation as a tree of JsonElements. We can add/ insert an additional property to JSON string by using the getAsJsonObject() method of JSonElement. This method returns to get the element as JsonObject.Syntaxpublic JsonObject getAsJsonObject()Exampleimport com.google.gson.*; public class AddPropertyGsonTest { public static void main(String[] args) { Gson gson = new GsonBuilder().setPrettyPrinting().create(); // pretty print JSON Student student = new Student("Adithya"); ...
Read MoreHow to convert an array to JSON Array using JSON-lib API in Java?
A Java array is an object which stores multiple variables of the same type, it can hold primitive types and object references whereas JSONArray is an ordered sequence of values. Its external text form is a string wrapped in square brackets with commas separating the values, an internal form is an object having get() and opt() methods for accessing the values by index and element() method for adding or replacing values. In the first step, we can create an Object[] array and pass this parameter as an argument to the toJSON() of JSONSerializer class and typecasting it to get the ...
Read MoreHow can we sort a JSONObject in Java?
A JSONObject is an unordered collection of a key, value pairs, and the values can be any of these types like Boolean, JSONArray, JSONObject, Number and String. The constructor of a JSONObject can be used to convert an external form JSON text into an internal form whose values can be retrieved with the get() and opt() methods or to convert values into a JSON text using the put() and toString() methods.In the below example, we can sort the values of a JSONObject in the descending order.Exampleimport org.json.*; import java.util.*; public class JSonObjectSortingTest { public static void main(String[] ...
Read MoreHow to create a class and object in JShell in Java 9?
JShell is a new java shell tool released in java 9. It is the first official REPL (Read-Evaluate-Print-Loop) application. This tool helps in executing and evaluating simple java programs and logics such as statements, loops, expressions, and etc. Java REPL provides a simple programming environment in the command prompt. It can read the input, evaluate it and print the output.In the below example we can able to create a class and object in JShell using command prompt.Examplejshell> class Employee { ...> private String name; ...> Employee(String name) { ...> this.name=name; ...> ...
Read MoreHow to deserialize a JSON string using @JsonCreator annotation in Java?
The @JsonProperty annotation can be used to indicate the property name in JSON. This annotation can be used for a constructor or factory method. The @JsonCreator annotation is useful in situations where the @JsonSetter annotation cannot be used. For instance, immutable objects do not have any setter methods, so they need their initial values injected into the constructor.@JsonProperty - ConstructorExampleimport com.fasterxml.jackson.annotation.*; import java.io.IOException; import com.fasterxml.jackson.databind.*; public class JsonCreatorTest1 { public static void main(String[] args) throws IOException { ObjectMapper om = new ObjectMapper(); String jsonString = ...
Read MoreHow to define alternate names to a field using Jackson in Java?
The @JsonAlias annotation can define one or more alternate names for the attributes accepted during the deserialization, setting the JSON data to a Java object. But when serializing, i.e. getting JSON from a Java object, only the actual logical property name is used instead of the alias.Syntax@Target(value={ANNOTATION_TYPE, FIELD, METHOD, PARAMETER}) @Retention(value=RUNTIME) public @interface JsonAliasExampleimport com.fasterxml.jackson.annotation.*; import com.fasterxml.jackson.core.*; import com.fasterxml.jackson.databind.*; import java.io.*; public class ObjectToJsonTest { public static void main(String[] args) throws JsonProcessingException { ObjectMapper mapper = new ObjectMapper(); Technology tech = new Technology("Java", "Oracle"); ...
Read MoreJShell in Java 9?
JShell is a new concept introduced in Java 9 version. It provides Java with REPL (Read-Eval-Print-Loop) ability. By using JShell, we can test the java-based logic and expressions without compiling it. REPL acts as an immediate feedback loop and has a great effect on productivity in that particular language.Step 1: Open Command Prompt and type JShell.Microsoft Windows [Version 6.3.9600] (c) 2013 Microsoft Corporation. All rights reserved. C:\Users\User>JShell | Welcome to JShell -- Version 9.0.4 | For an introduction type: /help intro jshell>Step 2: Type /help (to view JShell commands) in the JShell command window once it starts running.jshell> /help | Type ...
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