Found 9326 Articles for Object Oriented Programming

The Assignment OperatorsFollowing are the assignment operators supported by Java language −OperatorDescriptionExample=Simple assignment operator. Assigns values from right side operands to left side operand.C = A + B will assign value of A + B into C+=Add AND assignment operator. It adds right operand to the left operand and assigns the result to left operand.C += A is equivalent to C = C + A-=Subtract AND assignment operator. It subtracts the right operand from the left operand and assigns the result to left operand.C -= A is equivalent to C = C � A*=Multiply AND assignment operator. It multiplies right ... Read More

Let us look at a simple code first that will print the words Hello World.ExampleLive Demopublic 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 ... Read More

If we compare a float and a double value with .5 or .0 or .1235 (ending with 5 or 0), then == operator returns true, otherwise it will return false. See the below example.ExampleLive Demopublic class Tester {    public static void main(String[] args) {       double d1 = 2.5;       float f1 = 2.5f;       System.out.println(d1 == f1);       double d2 = 2.4;       float f2 = 2.4f;       System.out.println(d2 == f2);    } }Outputtrue falseThe reason behind this logic is the approximation of float and ... Read More

When we assigned an int to Integer object, it is first converted to an Integer Object and then assigned. This process is termed as autoboxing. But there are certain things which you should consider while comparison of such objects using == operator. See the below example first.ExampleLive Demopublic class Tester {    public static void main(String[] args) {       Integer i1 = new Integer(100);       Integer i2 = 100;               //Scenario 1:       System.out.println("Scenario 1: " + (i1 == i2));       Integer i3 = ... Read More

The java.lang.Enum class is the common base class of all Java language enumeration types.Class DeclarationFollowing is the declaration for java.lang.Enum class -public abstract class Enum    extends Object       implements Comparable, SerializableWe can compare enum variables using the following ways.Using Enum.compareTo() method. compareTo() method compares this enum with the specified object for order.Using Enum.equals() method. equals() method returns true if the specified object is equal to this enum constant.Using == operator. The == operator checks the type and makes a null-safe comparison of the same type of enum constants.ExampleLive Demopublic class Tester {    // enum showing topics ... Read More

Prior to Java 2, Java provided ad hoc classes such as Dictionary, Vector, Stack, and Properties to store and manipulate groups of objects. Although these classes were quite useful, they lacked a central, unifying theme. Thus, the way that you used Vector was different from the way that you used Properties.The collections framework was designed to meet several goals, such as −The framework had to be high-performance. The implementations for the fundamental collections (dynamic arrays, linked lists, trees, and hash tables) were to be highly efficient.The framework had to allow different types of collections to work in a similar manner ... Read More

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.ExampleLive Demopublic class Tester {    public ... Read More

Internet connectivity can be checked using java.net.URL and java.net.URLConnection class. Following are the required steps.Create a URL object and pass it the URL say GoogleCall URL.openConnection() method to get a URLConnection object.Call URLConnection.connect() method to check the internet connectivity. connect() method opens a communications link to the resource referenced by the passed URL if a connection has not already been established.Exampleimport java.io.IOException; import java.net.MalformedURLException; import java.net.URL; import java.net.URLConnection; public class Tester {    public static void main(String[] args) {       try {          URL url = new URL("http://www.google.com");          URLConnection connection ... Read More

Checked exceptionsA checked exception is an exception that occurs at the compile time, these are also called as compile time exceptions. These exceptions cannot simply be ignored at the time of compilation, the programmer should take care of (handle) these exceptions.For example, if you use FileReader class in your program to read data from a file, if the file specified in its constructor doesn't exist, then a FileNotFoundException occurs, and the compiler prompts the programmer to handle the exception.ExampleLive Demoimport java.io.File; import java.io.FileReader; public class FilenotFound_Demo {    public static void main(String args[]) {         ... Read More

The java.io.File class provides useful methods on file. This example shows how to check a file hidden or not by using the file.isHidden() method of File class.Exampleimport java.io.File; public class Main {    public static void main(String[] args) {       File file = new File("C:/java.txt");       System.out.println(file.isHidden());    } }ResultThe above code sample will produce the following result (if the file "java.txt" exists and is hidden in 'C' drive).true