Java Articles - Page 180 of 445

A Java class file has a ".class" extension and contains the Java bytecode. This class file can be executed by the Java Virtual Machine (JVM). A  ".class" file is created as a result of successful compilation by the Java compiler from the ".java" file. Each class in the .java file is compiled into a separate class file if the ".java " file has more than one class.Exampleclass A {    A() {       System.out.println("This is class A");    } } class B {    B() {       System.out.println("This is class B");    } } class C { ... Read More

When a value is assigned to a variable that is less than the minimum allowed value for that variable, then an underflow occurs. There is no exception thrown by the JVM if an underflow occurs in Java and it is the responsibility of a programmer to handle the underflow conditions.Examplepublic class UnderlowTest {    public static void main(String[] args) {       int num1 = -2147483648;       int num2 = -1;       System.out.println("Number 1: " + num1);       System.out.println("Number 2: " + num2);       long sum = (long)num1 + (long)num2;     ... Read More

A JTable provides a very flexible possibility to create and display tables. The TableModel interface defines methods for objects that specify the contents of a table. The AbstractTableModel class is typically extended to provide a custom implementation of a model table. A JTable class provides the ability to edit tables using the method setCellEditor() allows an object of the TableCellEditor interface.We can filter a table using the setRowFilter() method of TableRowSorter class.Exampleimport java.awt.*; import java.awt.event.*; import java.util.regex.*; import javax.swing.*; import javax.swing.table.*; public class FilterTableTest extends JFrame {    private JTable table;    private TableModel model;    public FilterTableTest() {       setTitle("FilterTable Test");       ... Read More

No, the "this" keyword cannot be used to refer to the static members of a class. This is because the “this” keyword points to the current object of the class and the static member does not need any object to be called. The static member of a class can be accessed directly without creating an object in Java. Example public class StaticTest { static int a = 50; static int b; static void show() { System.out.println("Inside the show() method"); b = a + 5; ... Read More

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