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Object Oriented Programming Articles
Page 294 of 589
Compilation and execution of Java Program
Let us look at a simple code first that will print the words Hello World.Examplepublic class MyFirstJavaProgram { /* This is my first java program. * This will print 'Hello World' as the output */ public static void main(String []args) { System.out.println("Hello World"); // prints Hello World } }Let's look at how to save the file, compile, and run the program. Please follow the subsequent steps −Open notepad and add the code as above.Save the file as: MyFirstJavaProgram.java.Open a command prompt window and go to the ...
Read MoreAssigning long values carefully in java to avoid overflow
In case of having the operation of integer values in Java, we need to be aware of int underflow and overflow conditions. Considering the fact that in Java, The int data type is a 32-bit signed two's complement integer having a minimum value of -2, 147, 483, 648 and a maximum value of 2, 147, 483, 647. If a value goes beyond the max value possible, the value goes back to minimum value and continue from that minimum. In a similar way, it happens for a value less than the min value. Consider the following example.Examplepublic class Tester { ...
Read MoreAssigning values to static final variables in java
In java, a non-static final variable can be assigned a value at two places.At the time of declaration.In constructor.Examplepublic class Tester { final int A; //Scenario 1: assignment at time of declaration final int B = 2; public Tester() { //Scenario 2: assignment in constructor A = 1; } public void display() { System.out.println(A + ", " + B); } public static void main(String[] args) { Tester tester = new Tester(); ...
Read MoreSleeping for a while in Java
You can sleep for any period of time from one millisecond up to the lifetime of your computer. For example, the following program would sleep for 3 seconds −Exampleimport java.util.*; public class SleepDemo { public static void main(String args[]) { try { System.out.println(new Date( ) + ""); Thread.sleep(5*60*10); System.out.println(new Date( ) + ""); } catch (Exception e) { System.out.println("Got an exception!"); } } }This will produce the following result −OutputSun May 03 18:04:41 GMT 2009 Sun May 03 18:04:51 GMT 2009
Read MoreDate Parsing using SimpleDateFormat
The SimpleDateFormat class has parse() method, which tries to parse a string according to the format stored in the given SimpleDateFormat object.Exampleimport java.util.*; import java.text.*; public class DateDemo { public static void main(String args[]) { SimpleDateFormat ft = new SimpleDateFormat ("yyyy-MM-dd"); String input = args.length == 0 ? "1818-11-11" : args[0]; System.out.print(input + " Parses as "); Date t; try { t = ft.parse(input); System.out.println(t); } catch (ParseException e) { System.out.println("Unparseable using " + ft); } } }A sample run of the above program would produce the following result −Output1818-11-11 Parses as Wed Nov 11 00:00:00 EST 1818
Read MoreDifference between super() and this() in Java
Following are the notable differences between super() and this() methods in Java. super()this()Definitionsuper() - refers immediate parent class instance.this() - refers current class instance.InvokeCan be used to invoke immediate parent class method.Can be used to invoke current class method.Constructorsuper() acts as immediate parent class constructor and should be first line in child class constructor.this() acts as current class constructor and can be used in parametrized constructors.OverrideWhen invoking a superclass version of an overridden method the super keyword is used.When invoking a current version of an overridden method the this keyword is used.Exampleclass Animal { String name; Animal(String name) { ...
Read MoreAddition and Concatenation in Java
'+' operator in java can be used to add numbers and concatenate strings. Following rules should be considered.Only numbers as operands then result will be a number.Only strings as operands then result will be a concatenated string.If both numbers and strings as operands, then numbers coming before string will be treated as numbers.If both numbers and strings as operands, then numbers coming after string will be treated as a string.Above rule can be overridden using brackets().ExampleCreate a java class named Tester.Tester.javapublic class Tester { public static void main(String args[]) { //Scenario 1: Only ...
Read Moreclone() method in Java
Java provides an assignment operator to copy the values but no operator to copy the object. Object class has a clone method which can be used to copy the values of an object without any side-effect. Assignment operator has a side-effect that when a reference is assigned to another reference then a new object is not created and both the reference point to the same object. This means if we change the value in one object then same will reflect in another object as well. clone() method handles this problem. See the below example.Examplepublic class Tester { public static ...
Read MoreCoupling in Java
Coupling refers to the usage of an object by another object. It can also be termed as collaboration. This dependency of one object on another object to get some task done can be classified into the following two types −Tight coupling - When an object creates the object to be used, then it is a tight coupling situation. As the main object creates the object itself, this object can not be changed from outside world easily marked it as tightly coupled objects.Loose coupling - When an object gets the object to be used from the outside, then it is a loose coupling ...
Read MoreCopyOnWriteArraySet Class in Java
Class declarationpublic class CopyOnWriteArraySet extends AbstractSet implements SerializableCopyOnWriteArraySet class uses CopyOnWriteArrayList internally for all of its operations and thus possesses the basic properties of CopyOnWriteArrayList.CopyOnWriteArraySet is a thread-safe.CopyOnWriteArraySet is to be used in Thread based environment where read operations are very frequent and update operations are rare.Iterator of CopyOnWriteArraySet will never throw ConcurrentModificationException.Any type of modification to CopyOnWriteArraySet will not reflect during iteration since the iterator was created.Set modification methods like remove, set and add are not supported in the iteration. This method will throw UnsupportedOperationException.CopyOnWriteArraySet MethodsFollowing is the list of important methods available in the CopyOnWriteArraySet class.Sr.No.Method & ...
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