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Checking internet connectivity in Java
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 MoreAutomatic resource management in Java
automatic resource management or try-with-resources is a new exception handling mechanism that was introduced in Java 7, which automatically closes the resources used within the try-catch block.ResourceA resource is an object which is required to be closed once our program finishes. For example, a file is read, database connection and so on.UsageTo use the try-with-resources statement, you simply need to declare the required resources within the parenthesis, and the created resource will be closed automatically at the end of the block. Following is the syntax of the try-with-resources statement.Syntaxtry(FileReader fr = new FileReader("file path")) { // use the resource ...
Read MoreWhat are the 6 ways to use this keyword in Java?
this can be used to get the current object.this can be used to invoke current object's method.this() can be used to invoke current class constructorthis can be passed as a parameter to a method call.this can be passed as a parameter to a constructor.this can be used to return the current object from the method.
Read MoreJava (JVM) Memory Types
Java Virtual Machine is a program/software which takes Java bytecode (.class files)and converts the byte code (line by line) into machine understandable code.JVM contains a module known as a class loader. A class loader in JVM loads, links and, initializes a program. It−Loads the class into the memory. Verifies the byte code instructions.Allocates memory for the program.The memory in the JVM is divided into five different parts namely− Method area− The method area stores the class code − code of the variables and methods. Heap − The Java objects are created in this area. Java Stack− While running methods the results are stored in ...
Read MoreHow is the java memory pool divided?
Java memory pool is divided into 5 parts namely −Method area − The method area stores the class code − code of the variables and methods.Heap−The Java objects are created in this area.Java Stack− While running methods the results are stored in the stack memory.PC registers− These contain the address of the instructions of the methods.Native method stacks− Similar to Java stack, native methods are executed on the Native method stacks.
Read MoreBest practice for variable and method naming in Java
All Java components require names. Names used for classes, variables and methods are called identifiers. In Java, there are several points to remember about identifiers. They are as follows -All identifiers should begin with a letter (A to Z or a to z), currency character ($) or an underscore (_). After the first character, identifiers can have any combination of characters.A keyword cannot be used as an identifier. Most importantly, identifiers are case sensitive. Examples of legal identifiers: age, $salary, _value, __1_value. Examples of illegal identifiers: 123abc, -salary.
Read MoreWebsites every Java developer should bookmark
There are many sites which are a good resource to learn java. Following is the list of most popular websites.Tutorialspoint - www.tutorialspoint.comStackOverflow - www.stackoverflow.comDZone - www.dzone.comWikipedia - www.wikipedia.orgIBM Developer Works - www.ibm.com/developerworks/java/TechGig - www.techgig.comGitHub - www.github.comJava documentation - docs.oracle.com/javase/Coursera - www.coursera.org/JavaWorld - www.javaworld.com/
Read MoreHow to pass a function as a parameter in Java
Yes. From Java 8 onwards, we can do so using method references.Method references help to point to methods by their names. A method reference is described using "::" symbol. A method reference can be used to point the following types of methods −Static methodsInstance methodsConstructors using new operator (TreeSet::new)Method Reference ExampleCreate the following Java program using any editor of your choice in, say, C:\> JAVA.Java8Tester.java Live Demo import java.util.List; import java.util.ArrayList; public class Java8Tester { public static void main(String args[]) { List names = new ArrayList(); names.add("Mahesh"); names.add("Suresh"); names.add("Ramesh"); ...
Read MoreHow to return 2 values from a Java method
A method can give multiple values if we pass an object to the method and then modifies its values. See the example below −Examplepublic class Tester { public static void main(String[] args) { Model model = new Model(); model.data1 = 1; model.data2 = 2; System.out.println(model.data1 + ", " + model.data2); changeValues(model); System.out.println(model.data1 + ", " + model.data2); } public static void changeValues(Model model) { model.data1 = 100; model.data2 = 200; } } class Model { int data1; int data2; }Output1, 2 100, 200
Read MoreHow to filter an array in Java
You can use List.removeAll() method to filter an array. exampleimport java.util.ArrayList; import java.util.List; public class Tester { public static void main(String[] args) { List list = new ArrayList(); list.add("A"); list.add("B"); list.add("C"); list.add("D"); list.add("E"); list.add("F"); list.add("G"); list.add("H"); List ...
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