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Articles by Maruthi Krishna
Page 48 of 50
How to loop the program after an exception is thrown in java?
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 MoreWhen do IllegalStateException and IllegalArgumentException get thrown? in java?
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 MoreHandling IllegalComponentStateException in java.
It is the sub class of IllegalStateException, This indicates that AWT component is not in an appropriate state i.e. if you are working with components but, not using them properly leads to this exception. There are several scenarios where this exception occursExampleIn the following example we are trying to build a sample login form here after setting the visibility of the window to true, we are trying to set the location by platform true which is inappropriate.import java.awt.*; import java.awt.event.*; import javax.swing.*; public class LoginDemo extends JFrame implements ActionListener { JPanel panel; JLabel user_label, password_label, message; JTextField ...
Read MoreDifferent scenarios that cause NoSuchElementException in Java.
An exception is an issue (run time error) occurred during the execution of a program. When an exception occurs the program gets terminated abruptly and, the code past the line that generated the exception never gets executed. Each exception is represented by its respective class.NosuchElement ExceptionThis is a Runtime exception i.e. it occurs at the execution time.While accessing the contents of a collection, array or other objects using the accessor methods of an Enumeration, Iterator or, tokenizer, such as next() or nextElement(), if you try to get the elements from an empty object, or if you try to get the ...
Read MoreHow to create an immutable set in Java?
Whenever you need to create an object which cannot be changed after initialization you can define an immutable object. There are no specific rules to create immutable objects, the idea is to restrict the access of the fields of a class after initialization.A Set is an interface in collection framework, which does not allow duplicate values.You need to keep following points in mind while creating an immutable set −We should not be able to add or delete elements from it.we should not be able to add null values to an immutable set.Once you create an immutable set you cannot add ...
Read MoreWhat is a variable, field, property in Java?
In programming to hold data members we use variables, Java you can declare three types of variables namely, Local variables − Variables defined inside methods, constructors or blocks are called local variables. The variable will be declared and initialized within the method and the variable will be destroyed when the method has completed.Instance variables − Instance variables are variables within a class but outside any method. These variables are initialized when the class is instantiated. Instance variables can be accessed from inside any method, constructor or blocks of that particular class.Class (static) variables − Class variables are variables declared within ...
Read MoreHow to include current date when logging exceptions to a file with FileOutputStream in java?
There are several logging frame works available to log your data into files. You can also define your own method. In either cases to add the current time to your logged exception you can use the LocalDateTime class.It is an immutable class representing the date-time, it stores date-time as year-month-day-hour-minute-second. The now() method of this class returns the current date-time.Using this method concatenate the current date and time to your exception message and write to your required file.Exampleimport java.io.FileOutputStream; import java.io.IOException; import java.time.LocalDateTime; import java.util.Arrays; import java.util.Scanner; public class LoggingToFile { private static void writeLogToFile(Exception e) throws IOException { ...
Read MoreHow to access Static variable of Outer class from Static Inner class in java?
A class with in another class is known as inner class, you cannot declare a class static unless it is an inner class. A static inner class is just like other class variables. You can access it (static inner class) without instantiationExampleYou can access the static variable of an outer class just using the class name. Following Java example demonstrates how to access static variables of a class from a static inner class.public class Outer { static int data = 200; static class InnerDemo { public void my_method() { System.out.println("This is ...
Read MoreWhy interfaces don't have static initialization block when it can have static methods alone in java?
An interface in Java is similar to class but, it contains only abstract methods and fields which are final and static.A static method is declared using the static keyword and it will be loaded into the memory along with the class. You can access static methods using class name without instantiation.Static methods in an interface since java8Since Java8 you can have static methods in an interface (with body). You need to call them using the name of the interface, just like static methods of a class.ExampleIn the following example, we are defining a static method in an interface and accessing ...
Read MoreHow to access the object of a class without using the class name from a static context in java?
The only possible solution is to get the stack trace of the current thread. Get the class name using an element in the stack trace. Pass it to the forName() method of the class named Class.This returns a Class object and you can get an instance of this class using the newInstance() method.Examplepublic class MyClass { String name = "Krishna"; private int age = 25; public MyClass() { System.out.println("Object of the class MyClass"); System.out.println("name: "+this.name); System.out.println("age: "+this.age); } public static void demoMethod() throws Exception { ...
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