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Object Oriented Programming Articles
Page 333 of 589
How to convert a List to JSON array using the Jackson library in Java?
JSON is used in Java applications in APIs, file storage, and data communication between systems. Sometimes, we need to convert a list into a JSON array. In this article, we will learn how to convert a list to JSON array using the Jackson library. Jackson Library It is a library that is used in Java to work with JSON data. It provides APIs to serialize Java objects into JSON and deserialize JSON back into Java objects. If you want to read more about the Jackson library, you can refer Jackson library. There are mainly three components of Jackson - ...
Read MoreHow to compile & run a Java program using Command Prompt?
Command prompt is a command line interface that accepts text-based inputs or commands and performs tasks based on those command. Nowadays, there are various integrated development environments (IDEs) that are available to compile, build, and run Java programs within their environment. However, we can also compile and run Java programs using the Command Prompt. Compiling and Running Java Programs using CLI To compile and run Java programs outside the IDEs using the Command Prompt, we need to install the JDK and set its path in our system. To set up the development environment for Java on your local machine, we ...
Read MoreWhy do we get ClassNotFoundException when the class exists in Java?
Whenever we try to load a class, ClassNotFoundException occurs when the application tries to load a class at runtime using methods like Class.forName() or ClassLoader.loadClass(), but the JVM cannot locate the class in the classpath. The following are the reasons of ClassNotFoundException occurence and they are - Incorrect Class Name Incorrect Package Structure ...
Read MoreHow to change/increase the heap size of the Java Virtual Machine in Java?
A Java program can execute in the Java Virtual Machine (JVM) and uses the heap memory to manage the data. If our Java program requires more memory, there is a possibility that the Java Virtual Machine(JVM) will begin to throw OutOfMemoryError instances when attempting to instantiate an object in Java. How to change/increase the JVM Heap Size? In Java, it is possible to increase the heap size allocated by the JVM: -Xms: Set an initial Java heap size JVM automatically manages the heap memory but we can ...
Read MoreCan we change method signature in overriding in Java?
No, you cannot change the method signature while overriding. Changing the method signature becomes method overloading, not overriding. Now, let's understand why - Method Signature In Java, a method signature consists of - Method name: It is used to call the method. Parameter list: It includes the number, type, and order of parameters. Note: The method signature does not include return type, ...
Read MoreDifference between constants and final variables in Java?
In Java, both constants and final variables are used to define variables that cannot be changed after initialization. But they have some differences. In this article, we will learn how they are different. Final Variable A final variable in Java means you cannot reassign it after it has been initialized. Whether it is a local variable, instance variable, or static variable, once it's assigned, the value cannot be changed. If you try to do so, a compile-time error will be generated. public class FinalExample { public static void main(String args[]) { ...
Read MoreIs Swing thread-safe in Java?
No, Java Swing components are not thread-safe in Java. This means that whenever Swing components should be accessed or changed, it is done mostly by using a single thread, the EDT. Why Swing Components are not thread-safe One of the main reasons Java Swing is not thread-safe is to simplify the task of extending its components. Another reason for that Java Swing is not thread-safe due to the overhead involved in obtaining and releasing locks and restoring the state. Below are some methods given by Swing for safe operation with its UI: SwingUtilities.invokeLater(): In ...
Read MoreTrigraphs in C++
Trigraphs in C++ are special three-character sequences that represent a certain single character, which may not be available on some keyboards or systems. Previously, the ISO-646 character set did not have all the characters of the C syntax; therefore, some systems with their keyboard and display faced problems while dealing with those few characters.So the trigraphs have been introduced, which start with two question marks (??) and are further followed by a third character, which the compiler considers as a particular equivalent single-character. Trigraphs Table in C++ There are a total of nine trigraphs available in C++; here is the ...
Read MoreHow to get all the keys of a JSON object using GSON in Java?
JSON is the data interchange format that stores values in key-value pairs. (To learn more about JSON, you can refer to the JSON tutorial). So, as we have key and value in JSON, we will try to get all those keys using the Gson library. Gson Library:Â Retrieving all the keys of a JSON Gson is a third-party Java library developed by Google. It is used for converting Java objects to JSON and vice versa. To know more about Gson, refer to the Gson tutorial. We can use the keySet() method of JsonObject class to get all the keys of a ...
Read MoreWhat are the differences between the TableCellRenderer and TableCellEditor in Java?
In this article, we will learn about the differences between the TableCellRenderer and TableCellEditor in Java. The JTable interface in Java Swing has these important interfaces called TableCellRenderer and TableCellEditor. Though they serve different purposes, they complement each other in defining the table cells' render and edit functions. TableCellRenderer A TableCellRenderer creates a component that displays the value of a JTable cell. The default renderer uses JLabel to display the value of each table cell. The TableCellRenderer interface can be specified in three ways : By the class of the object to be ...
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