Java Articles - Page 185 of 440

This article will discuss how to implement a Queue using a Stack in Java. It will briefly introduce the Queues and Stacks, and provide a suitable example that shows their implementation. Queues in Java In Java, the Queue class extends the Collection interface, and it supports the insert and remove operations using a FIFO (First-in-First-Out). The last element added to the end of the queue can become the first element to be removed from the queue. The following diagram will give you a better understanding of the Queue: Stacks in Java In Java, a Stack is a subclass (child class) ... Read More

Converting a character array to a reader in Java means treating the array as a stream of characters to be read sequentially. Let's quickly learn about character array and its creation in Java: In Java, a character array is an array that holds elements of only char type, and it is also used to store a sequence of characters. Following is the syntax to define a character array in Java: char char_array_name[] = {'char1', 'char2', 'char3'....} or char char_array_name[] = new char[size]; Here, char_array_name: The name of the character array. ... Read More

No, for that matter to throw any exception explicitly you need to create an object of that exception and throw it using the throw keyword.Without creating an object you cannot throw an exception explicitly, you might create a scenario that causes the respective exception.ExampleFollowing Java program throws a NullPointerExceptionpublic class ExceptionExample {    public static void main(String[] args) {       System.out.println("Hello");       NullPointerException nullPointer = new NullPointerException();       throw nullPointer;    } }OutputHello Exception in thread "main" java.lang.NullPointerException    at MyPackage.ExceptionExample.main(ExceptionExample.java:6)

Read the inputs and perform the required calculations within a method. Keep the code that causes exception in try block and catch all the possible exceptions in catch block(s). In each catch block display the respective message and call the method again.ExampleIn the following example we have an array with 5 elements, we are accepting two integers from user representing positions in the array and performing division operation with them, if the integer entered representing the positions is more than 5 (length of the exception) an ArrayIndexOutOfBoundsException occurs and, if the position chosen for denominator is 4 which is 0 ... Read More

An exception is an issue (run time error) occurred during the execution of a program. When an exception occurred the program gets terminated abruptly and, the code past the line that generated the exception never gets executed.Printing the Exception messageYou can print the exception message in Java using one of the following methods which are inherited from Throwable class.printStackTrace() − This method prints the backtrace to the standard error stream.getMessage() − This method returns the detail message string of the current throwable object.toString() − This message prints the short description of the current throwable object.Exampleimport java.util.Scanner; public class PrintingExceptionMessage { ... Read More

In Java there is default value for every type, when you don’t initialize the instance variables of a class Java compiler initializes them on your be-half with these values. Null is the default value of the object type, you can also manually assign null to objects in a method.Object obj = null;But, you cannot use an object with null value or (a null value instead of an object) if you do so, a NullPointerException will be thrown.Examplepublic class Demo {    String name = "Krishna";    int age = 25;    public static void main(String args[]) {       ... Read More

In Java there is default value for every type, when you don’t initialize the instance variables of a class Java compiler initializes them on your be-half with these values. Null is the default value of the object type, you can also manually assign null to objects in a method.Object obj = null;But, you cannot use an object with null value or (a null value instead of an object) if you do so, a NullPointerException will be thrown.Examplepublic class Demo {    String name = "Krishna";    int age = 25;    public static void main(String args[]) {       ... Read More

IllegalStateException:This exception is thrown when you call a method at illegal or inappropriate time an IlleagalStateException is generated.For example, the remove() method of the ArrayList class removes the last element after calling the next() or previous methods.After removing the element at the current position you need to move to the next element to remove it i.e. per one call of the next() method you can invoke this remove() method only once.Since the initial position of the list (pointer) will be before the first element, you cannot invoke this method without calling the next method.If you invoke the remove() method otherwise ... Read More

Whenever you pass inappropriate arguments to a method or constructor, an IllegalArgumentException is thrown. It is a Runtime exception therefore there is no need to handle this at the time of compilation.ExampleThe valueOf() method of the java.sql.Date class accepts a String representing a date in JDBC escape format yyyy-[m]m-[d]d and converts it into a java.sql.Date object.import java.sql.Date; import java.util.Scanner; public class IllegalArgumentExample {    public static void main(String args[]) {       Scanner sc = new Scanner(System.in);       System.out.println("Enter your date of birth in JDBC escape format (yyyy-mm-dd) ");       String dateString = sc.next();   ... Read More

An exception is an issue (run time error) occurred during the execution of a program. Here are some example scenarios −If you have an array of size 10 if a line in your code tries to access the 11th element in this array.If you are trying to divide a number with 0 which (results to infinity and JVM doesn’t understand how to valuate it).When exception occurs the program terminates abruptly at the line that caused exception, leaving the remaining part of the program unexecuted. To prevent this, you need to handle exceptions.There are two types of exceptions in java.Unchecked Exception ... Read More