Java Articles - Page 179 of 440

A Java Class is stored in the form of byte code in a .class file after it is compiled. The ClassLoader loads the class of the Java program into memory when it is required. The ClassLoader is hierarchical and so if there is a request to load a class, it is delegated to the parent class loader.The types of ClassLoader in Java are given as followsBootstrap ClassLoaderExtensions ClassLoaderSystem ClassLoaderExamplepublic class ClassLoaderTest {    public static void main(String[] args) {       System.out.println("class loader for this class: " + ClassLoaderTest.class.getClassLoader());       System.out.println("class loader for DNSNameService: " + sun.net.spi.nameservice.dns.DNSNameService.class.getClassLoader());     ... Read More

Yes, we can have an empty catch block. But this is a bad practice to implement in Java.Generally, the try block has the code which is capable of producing exceptions, if anything wrong in the try block, for instance,  divide by zero, file not found,  etc. It will generate an exception that is caught by the catch block. The catch block catches and handles the exception. If the catch block is empty then we will have no idea what went wrong within our code.Examplepublic class EmptyCatchBlockTest {    public static void main(String[] args) {       try {          int a ... Read More

A JTable is a subclass of JComponent class for displaying complex data structures. A JTable can follow the Model View Controller (MVC) design pattern for displaying the data in rows and columns. A JTable will generate TableModelListener, TableColumnModelListener, ListSelectionListener, CellEditorListener and RowSorterListener interfaces.We can validate whether the JTable cell is empty or not by implementing the getValueAt() method of JTable class. If we click on the "Click Here" button, it will generate an action event and display a popup message like "Field is Empty" to the user.Exampleimport java.awt.*; import java.awt.event.*; import javax.swing.*; import javax.swing.table.*; public class JTableEmptyValidateTest extends JFrame {    private JPanel panel;    private JTable table;   ... Read More

A JTable is a subclass of JComponent class and it can be used to create a table with information displayed in multiple rows and columns. When a value is selected from a JTable, a TableModelEvent is generated, which is handled by implementing a TableModelListener interface.In the below program, we can display "No records available" text if the rows are not available in a JTable.Exampleimport java.awt.*; import java.awt.event.*; import javax.swing.*; import javax.swing.table.*; public class NoRecordTableTest extends JFrame {    private JPanel panel;    private JTable table;    private JScrollPane scrollPane;    public NoRecordTableTest() {       panel = new JPanel();       panel.setLayout(new BorderLayout()); ... Read More

This article will discuss how to print the first character of each word in a given string. For example, if we have the string "Hello John", the output should be H J. In Java, the String class is used to represent character strings. All string literals in a Java program are implemented as instances of the String class. Strings in Java are immutable, which means that once a string is created, its value cannot be changed. To print the first character of each word in a String, we have the following approaches - Using split() ... Read More

What are Generic Collections in Java? In Java, the Generic collections were introduced in Java 5. These collections disable the type-casting, and there is no need for explicit type-casting if we use generic collections. The generic collections are type-safe and detect type-related errors at compile time. It allows the datatypes to pass as parameters to classes or interfaces. The Compiler is responsible for checking the compatibility of the types. Syntax Following is the way to create generic collections in Java: class or interface Where type specifies the type of the object, such as: Integer, String, Character, etc.. You can create generic ... Read More

A JTree is a component that presents a hierarchical view of data. The user has the ability to expand or collapse individual sub-trees. A TreeNode interface defines the methods that must be implemented nodes of a JTree object. The DefaulMutableTreeNode class provides a default implementation of a TreeNode interface. We can disable the leaf of JTree by overriding the getTreeCellRendererComponent() method of DefaultTreeCellRenderer class.Syntaxpublic Component getTreeCellRendererComponent(JTree tree, Object value, boolean sel, boolean expanded, boolean leaf, int row, boolean hasFocus)Exampleimport java.awt.*; import javax.swing.tree.*; import javax.swing.*; public class JTreeLeafNodeDisableTest extends JFrame {    private TreeNode treeNode;    private JTree tree;    public JTreeLeafNodeDisableTest() {       setTitle("JTreeLeafNodeDisable Test");     ... Read More

In Java, a HashMap is a subclass of the AbstractMap class and is used to store key-value pairs. Each key in the map is mapped to a single value in the map, and the keys are unique.Printing Java HashMap Elements  We can insert a key only once in a map, and duplicate keys are not allowed, but the value can be mapped to multiple keys. We can add the elements using the put() method of the HashMap class and iterate over the elements using the Iterator interface. Java HashMap provides various ways to print its elements as follows: ... Read More

A JTree is a subclass of JComponent class that can be used to display the data with the hierarchical properties by adding nodes to nodes and keeps the concept of parent and child node. Each element in the tree becomes a node. The nodes are expandable and collapsible. We can implement the mouse right-click on each node of a JTree using the mouseReleased() method of MouseAdapter class and need to call show() method of JPopupMenu class to show the popup menu on the tree node.Exampleimport java.awt.*; import java.awt.event.*; import javax.swing.*; import javax.swing.tree.*; public class JTreeRightClickTest extends JFrame {    public JTreeRightClickTest() {       ... Read More

Yes, we can synchronize a run() method in Java using the synchronized keyword before this method. If this method is synchronized, only one thread can execute this on a given instance of the object at any point in time. Here is a code snippet that shows how to define the run() method as synchronized: @Override synchronized run(){ //code implementation } Here, the @Override annotation specifies that the run() method overrides a method from the Runnable interface, and synchronized is a reserved keyword in Java used to define a method or block as synchronized. Synchronization of a run() ... Read More